title: Willis Tower

text: Each of the "tubes" is a column-free module measuring , which set back at different stories. There are setbacks at the 50th, 66th, and 90th floors. The lowest 50 stories contain nine tubes and cover each. The northwest and southeast tubes terminate at the 50th floor. The 51st through 66th floors each span , above which the northeast and southwest tubes end. From the 67th to 90th floors, each story is shaped like a cross, covering . The north, east, and south tubes end at the 90th floor; the remaining west and center tubes reach 108 floors, with an area of on each of the top stories.


title: Willis Tower

text: The Sears Tower was the first building to use this innovative design. It was both structurally efficient and economic: at 1,450 feet, it provided more space and rose higher than the Empire State Building and cost much less per unit area. The system would prove highly influential in skyscraper construction and has been used in most supertall buildings since, including the world's current tallest building, the Burj Khalifa. In February 1982, two television antennas were added to the structure, increasing its total height to . The western antenna was later extended, bringing the overall height to on June 5, 2000, to improve reception of local NBC station WMAQ-TV.


title: Willis Tower

text: The perimeter of the Willis Tower contains columns that are spaced apart on their centers. The facade is made of anodized aluminum and black glass. Alcoa manufactured of aluminum sheeting for the building's facade. Black bands appear on the tower around the 29th–32nd, 64th–65th, 88th–89th, and 104th–108th floors. These elements are louvers to ventilate the building's environmental support systems and obscure its belted trusses. The rest of the facade is made of 16,000 rectangular windows. all of which measure and are tinted with bronze.


title: Willis Tower

text: Outside the building, there was originally a plaza made of pink granite. In the late 2010s, a three-level wing was built along the western and southern sides of the tower replacing the tower. The roof garden above the annex spans . The annex contains a facade of black steel and aluminum, similar to in the original building. The Jackson Boulevard facade of the annex contains an artwork by Olafur Eliasson, entitled "Atmospheric wave wall". The work, measuring across, comprises almost 2,000 blue-and-green steel tiles, which are decorated with hexagonal motifs. The wall is backlit at night.


title: Willis Tower

text: The interior includes of steel, of aluminum, and of concrete flooring. The building contains diagonal columns only on the two stories immediately below each of the setbacks, thus reducing shear stress. The interior of the building could not contain diagonal beams, since these would have obstructed the connections between each of the "tubes". Therefore, the columns and the horizontal beams on each story are connected by rigid joints. The superstructure was designed to withstand wind gusts of , which on average would occur once every hundred years. According to the "Chicago Tribune", the top of the building would be able to bend by as much as , returning to its normal position within 7.2 seconds.


title: Willis Tower

text: The Willis Tower's basement extends deep, resting on a concrete slab. The ground directly beneath the building was largely made of clay; the underlying layer of limestone was as much as beneath ground level. As a result, the foundation was excavated using 201 caissons, of which 114 reached the underlying limestone. The caissons created holes that measured up to across. Some holes at the northwestern and northeastern corners of the site filled up with groundwater and had to be drained. Workers next placed steel tubes into the holes, then poured concrete around the tubes.


title: Willis Tower

text: During the Sears Tower's construction, SOM and Chicago government officials considered adding "smoke free and fire free" areas to the building, as well as a complete sprinkler system serving all floors. Neither of these features had previously been used in a structure in Chicago. Even though regulations did not require a fire sprinkler system, the building was equipped with one from the beginning. There are around 40,000 sprinkler heads in the building, installed at a cost of $4 million. When it was completed, the Sears Tower was heated electrically, unlike older structures that used gas heating. It included 145,000 light fixtures and a cooling system capable of 17,000 tons of refrigeration. Furthermore, the tower contained fire-suppression and communications systems for emergency use, which were powered by diesel generators. If there was a fire in one section of the building, the building's smoke-detection system would close off the fresh-air intake openings in that section, discharging smoke outdoors.


title: Willis Tower

text: Fifteen above-ground stories, as well as three of the basement levels, contain mechanical equipment. Above the Skydeck on the 103rd floor is a seven-story mechanical penthouse.


title: Willis Tower

text: The Sears Tower was planned with 103 elevators, including 14 double-deck elevators. The office stories are served by 97 elevator cabs; due to the presence of the double-deck elevators, these occupy 83 shafts. As designed, one bank of single-deck elevators connected the lobby to the lowest 28 stories. Banks of double-deck elevators traveled to "sky lobbies" at the 33rd/34th and 66th/67th floors, where passengers could transfer to local elevators. The 34th through 103rd stories were served by local elevators that operated from the sky lobbies. Two elevators also ran directly from the lobby to the Skydeck on the 103rd floor. , the elevators carried 5.8 million passengers per year.


title: Willis Tower

text: Six of the elevators are used for freight. One of the freight elevators served all stories, traveling to a height of . During a fire or another emergency, this elevator would be reserved for the Chicago Fire Department. Other elevators would be controlled from the 33rd floor. During a fire, elevators would be dispatched to the affected floors to assist with evacuation.


title: Willis Tower

text: The building also had 16 escalators, including a set of double-height escalators that traveled from the main lobby to the lower mezzanine. Another set of escalators connects the 33rd and 34th stories.


title: Willis Tower

text: When the building was completed, the main entrance was on Wacker Drive to the west. There was a plaza on the south side of the building, sloping upward toward Franklin Street to the east. The Franklin Street side of the building was lower than the Wacker Drive entrance, so the entrances on Franklin Street were actually below the plaza, leading to the building's lower mezzanine. Below ground level are three basement levels with a total area of . The basements included a 1,200-seat cafeteria, commercial space, service areas, and a loading dock for 17 trucks. The basement also contained a 150-spot parking garage.


title: Willis Tower

text: , the building's base covers and contains two lobbies for tenants. The building's tenants primarily enter from Wacker Drive and Franklin Street. Shoppers, restaurant patrons, and visitors to the Skydeck observation deck use the southern entrance on Jackson Boulevard. The Wacker Drive lobby contains "In the Heart of this Infinite Particle of Galactic Dust", a 2019 artwork by Jacob Hashimoto. It consists of over 7,000 rice-paper and resin disks that are hung from the ceiling. To honor Khan's contributions to skyscraper engineering design, the Structural Engineers Association of Illinois also commissioned a sculpture of him for the lobby of the Willis Tower.


title: Willis Tower

text: The commercial complex at the building's lowest stories is known as the Catalog, a reference to Sears' mail-order catalogs. The six-story complex includes numerous restaurants. It extends into three of the building's basement levels, as well as the three-story annex to the south and west of the tower. The roof of the annex includes a curved skylight with 240 glass panes, and the northern section of the annex's roof is supported by black columns that resemble those in the original tower. The Catalog also contains decorative details, such as handrails and staircase landings, which are inspired by elements of Chicago's "built environment". The third story of the Catalog contains a 30,000-square-foot coworking space operated by Convene.


title: Willis Tower

text: The Willis Tower observation deck, called the Skydeck, opened on June 22, 1974. Located on the 103rd floor, above ground level, it is the highest observation deck in the United States and one of Chicago's most famous tourist attractions. Tourists can experience how the building sways in wind and see far over the plains of Illinois and across Lake Michigan to Indiana, Michigan, and Wisconsin in clear conditions. Elevators reach the top in about 60 seconds, allowing occupants to feel the change in pressure as they ascend. The Skydeck competes with the John Hancock Center's observation floor a mile and a half away but reaching lower. Some 1.7 million tourists visit annually. A second observation deck on the 99th floor serves as a backup.


title: Willis Tower

text: In January 2009, a major renovation of the Skydeck began, including the installation of retractable glass balconies which extend approximately from the facade of the 103rd floor, overlooking South Wacker Drive. The all-glass boxes, informally dubbed "The Ledge", allow visitors to see the street below. The boxes, which can accommodate , opened to the public on July 2, 2009. On May 29, 2014, the laminated glass flooring of one of the boxes cracked while visitors were inside, but there were no injuries. The flooring of the same box cracked again on June 12, 2019. In May 2022 a fifth glass ledge opened on the west facade overlooking South Wacker Drive.


title: Willis Tower

text: When completed, the Sears Tower was the world's tallest building but not the world's tallest structure. Toronto's CN Tower was about taller, although the Council on Tall Buildings and Urban Habitat (CTBUH) does not consider the CN Tower to be a building, since it does not have floors from the ground up. The Willis Tower remains the third tallest building in the Americas and in the Western Hemisphere (after One World Trade Center and Central Park Tower in New York City). With a pinnacle height of , it is the third-tallest freestanding structure in the Americas. It is the 16th-tallest freestanding structure in the world by pinnacle height.


title: Willis Tower

text: When the Petronas Twin Towers in Kuala Lumpur, Malaysia, was completed in 1998, it claimed to be the tallest building in the world, measuring tall including decorative spires. Chicagoans objected to this claim on the basis that the Sears Tower's top floor was higher than that of either of the Petronas Towers. In the ensuing controversy, four categories of "tallest building" were created. Of these, Petronas was the tallest in the category of height to the top of architectural elements, meaning spires but not antennas. Taipei 101 in Taiwan claimed the record in three of the four categories in 2004, surpassing the Petronas Twin Towers in spire height and the Sears Tower in roof height and highest occupied floor. People suggested that Sears add cosmetics atop its tower to surpass Taipei 101, but this did not materialize. On August 12, 2007, the Burj Khalifa in Dubai was reported by its developers to have surpassed the tower in all height categories. Upon completion, One World Trade Center in New York City surpassed the Willis Tower through its structural and pinnacle heights, but not by roof, observation deck elevation, or highest occupied floor.


title: Willis Tower

text: Until 2000, the tower did not hold the record for being the tallest building by pinnacle height. From 1969 to 1978, this record was held by John Hancock Center, whose antenna reached a height of , taller than the Sears Tower's original height. One World Trade Center became taller by pinnacle height with the addition of a 359-foot (109.4-meter) antenna, bringing its total height to . In 1982, two antennas were installed which brought its total height to , making it taller than the John Hancock Center but not One World Trade Center. However, the extension of the tower's western antenna in June 2000 to allowed it to just barely claim the title of tallest building by pinnacle height.


title: Willis Tower

text: On May 25, 1981, Dan Goodwin, wearing a homemade Spider-Man suit while using suction cups, camming devices, and sky hooks, and despite several attempts by the Chicago Fire Department to stop him, made the first successful outside ascent of the tower. Goodwin was arrested at the top after the seven-hour climb and was later charged with trespassing. Goodwin stated that the reason he made the climb was to call attention to shortcomings in high-rise rescue and firefighting techniques. After a lengthy interrogation by Chicago's District Attorney and Fire Commissioner, Goodwin was officially released from jail.


title: Willis Tower

text: In August 1999, French urban climber Alain "Spiderman" Robert, using only his bare hands and bare feet, scaled the building's exterior glass and steel wall all the way to the top. A thick fog settled in near the end of his climb, making the last 20 stories of the building's glass and steel exterior slippery.


title: Willis Tower

text: Annually, since 2009, the Willis Tower has hosted SkyRise Chicago, the world's tallest indoor stair climb, as a charity event benefiting Shirley Ryan AbilityLab, where participants can (legally) climb the Willis Tower's 103-story staircase.


title: Willis Tower

text: Sears sold the tower in 1994 and vacated it by 1995, but retained naming rights through 2003. The new owners were rebuffed in renaming deals with CDW Corp in 2005 and the U.S. Olympic Committee in 2008. British insurance broker Willis Group Holdings leased more than of space on three floors in 2009. A Willis spokesman said the naming rights were obtained as part of the negotiations at no cost to Willis and the building was renamed Willis Tower on July 16, 2009.


title: Willis Tower

text: The naming rights are valid for 15 years, so it is possible that the building's name could change again as soon as 2024. The "Chicago Tribune" joked that the building's new name reminded them of the oft-repeated "What you talkin' 'bout, Willis?" catchphrase from the American television sitcom "Diff'rent Strokes" and considered the name-change ill-advised in "a city with a deep appreciation of tradition and a healthy ego, where some Chicagoans still mourn the switch from Marshall Field's to Macy's". This feeling was confirmed in a July 16, 2009, CNN article in which some Chicago-area residents expressed reluctance to accept the Willis Tower name, and in an article that appeared in the October 2010 issue of "Chicago" magazine that ranked the building among Chicago's 40 most important, the author pointedly refused to acknowledge the name change and referred to the building as the "Sears Tower". "Time" magazine called the name change one of the top 10 worst corporate name changes and pointed to negative press coverage by local news outlets and online petitions from angry residents. The naming rights issue continued into 2013, when Eric Zorn noted in the "Chicago Tribune" that "We're stubborn about such things. This month marked four years since the former Sears Tower was re-christened Willis Tower, and the new name has yet to stick."


title: Willis Tower

text: Many broadcast station transmitters are located at the top of Willis Tower. Each list is ranked by height from the top down. Stations at the same height on the same mast indicate the use of a diplexer into the same shared antenna. Due to its extreme height, FM stations (all class B) are very limited in power output.


title: Willis Tower

text: NOAA Weather Radio station KWO39 transmits off the tower at 162.550 MHz. Programmed by the National Weather Service Weather Forecast Office in Chicago, it is equipped with Specific Area Message Encoding (SAME), which sets off a siren on specially programmed weather radios to alert of an impending hazard.


title: Willis Tower

text: The building has appeared in numerous films and television shows set in Chicago such as "Ferris Bueller's Day Off", where Ferris and company visit the observation deck. "Late Night with Conan O'Brien" introduced a character called The Sears Tower Dressed In Sears Clothing when the show visited Chicago in 2006. The building is also featured in History Channel's "Life After People", in which it and other human-made landmarks suffer from neglect without humans around, collapsing two hundred years after people are gone.


title: Willis Tower

text: In the 2008 film "The Dark Knight", it is part of Gotham City. In the 2011 film "", it is featured in a number of scenes. In the 2013 film "Man of Steel", the tower is the location of the offices of the "Daily Planet".


title: Cretaceous–Paleogene extinction event

text: The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as sea turtles and crocodilians, no tetrapods weighing more than survived. It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day.


title: Cretaceous–Paleogene extinction event

text: In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.


title: Cretaceous–Paleogene extinction event

text: As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was caused by the impact of a massive asteroid , 66 million years ago, which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton. The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s, which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact. The fact that the extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid. A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any gypsum, the usual sulfate-containing sea floor rock in the region: the gypsum would have vaporized and dispersed as an aerosol into the atmosphere, causing longer-term effects on the climate and food chain. In October 2019, researchers reported that the event rapidly acidified the oceans, producing ecological collapse and, in this way as well, produced long-lasting effects on the climate, and accordingly was a key reason for the mass extinction at the end of the Cretaceous.


title: Cretaceous–Paleogene extinction event

text: Other causal or contributing factors to the extinction may have been the Deccan Traps and other volcanic eruptions, climate change, and sea level change. However, in January 2020, scientists reported that climate-modeling of the extinction event favored the asteroid impact and not volcanism.


title: Cretaceous–Paleogene extinction event

text: A wide range of terrestrial species perished in the K–Pg extinction, the best-known being the non-avian dinosaurs, along with mammals, birds, lizards, insects, plants, and all the pterosaurs. In the oceans, the K–Pg extinction killed off plesiosaurs and mosasaurs and devastated teleost fish, sharks, mollusks (especially ammonites, which became extinct), and many species of plankton. It is estimated that 75% or more of all species on Earth vanished. Yet the extinction also provided evolutionary opportunities: in its wake, many groups underwent remarkable adaptive radiation—sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene, evolving new forms such as horses, whales, bats, and primates. The surviving group of dinosaurs were avians, a few species of ground and water fowl, which radiated into all modern species of birds. Among other groups, teleost fish and perhaps lizards also radiated.


title: Cretaceous–Paleogene extinction event

text: The K–Pg extinction event was severe, global, rapid, and selective, eliminating a vast number of species. Based on marine fossils, it is estimated that 75% or more of all species were made extinct.


title: Cretaceous–Paleogene extinction event

text: The event appears to have affected all continents at the same time. Non-avian dinosaurs, for example, are known from the Maastrichtian of North America, Europe, Asia, Africa, South America, and Antarctica, but are unknown from the Cenozoic anywhere in the world. Similarly, fossil pollen shows devastation of the plant communities in areas as far apart as New Mexico, Alaska, China, and New Zealand.


title: Cretaceous–Paleogene extinction event

text: Despite the event's severity, there was significant variability in the rate of extinction between and within different clades. Species that depended on photosynthesis declined or became extinct as atmospheric particles blocked sunlight and reduced the solar energy reaching the ground. This plant extinction caused a major reshuffling of the dominant plant groups. Omnivores, insectivores, and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. No purely herbivorous or carnivorous mammals seem to have survived. Rather, the surviving mammals and birds fed on insects, worms, and snails, which in turn fed on detritus (dead plant and animal matter).


title: Cretaceous–Paleogene extinction event

text: In stream communities, few animal groups became extinct, because such communities rely less directly on food from living plants, and more on detritus washed in from the land, protecting them from extinction. Similar, but more complex patterns have been found in the oceans. Extinction was more severe among animals living in the water column than among animals living on or in the sea floor. Animals in the water column are almost entirely dependent on primary production from living phytoplankton, while animals on the ocean floor always or sometimes feed on detritus. Coccolithophorids and mollusks (including ammonites, rudists, freshwater snails, and mussels), and those organisms whose food chain included these shell builders, became extinct or suffered heavy losses. For example, it is thought that ammonites were the principal food of mosasaurs, a group of giant marine reptiles that became extinct at the boundary. The largest air-breathing survivors of the event, crocodyliforms and champsosaurs, were semi-aquatic and had access to detritus. Modern crocodilians can live as scavengers and survive for months without food, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous.


title: Cretaceous–Paleogene extinction event

text: After the K–Pg extinction event, biodiversity required substantial time to recover, despite the existence of abundant vacant ecological niches.


title: Cretaceous–Paleogene extinction event

text: The K–Pg boundary represents one of the most dramatic turnovers in the fossil record for various calcareous nanoplankton that formed the calcium deposits for which the Cretaceous is named. The turnover in this group is clearly marked at the species level. Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by a sharp increase in extinctions than by a decrease in speciation. The K–Pg boundary record of dinoflagellates is not so well understood, mainly because only microbial cysts provide a fossil record, and not all dinoflagellate species have cyst-forming stages, which likely causes diversity to be underestimated. Recent studies indicate that there were no major shifts in dinoflagellates through the boundary layer.


title: Cretaceous–Paleogene extinction event

text: Radiolaria have left a geological record since at least the Ordovician times, and their mineral fossil skeletons can be tracked across the K–Pg boundary. There is no evidence of mass extinction of these organisms, and there is support for high productivity of these species in southern high latitudes as a result of cooling temperatures in the early Paleocene. Approximately 46% of diatom species survived the transition from the Cretaceous to the Upper Paleocene, a significant turnover in species but not a catastrophic extinction.


title: Cretaceous–Paleogene extinction event

text: The occurrence of planktonic foraminifera across the K–Pg boundary has been studied since the 1930s. Research spurred by the possibility of an impact event at the K–Pg boundary resulted in numerous publications detailing planktonic foraminiferal extinction at the boundary; there is ongoing debate between groups which think the evidence indicates substantial extinction of these species at the K–Pg boundary, and those who think the evidence supports multiple extinctions and expansions through the boundary.


title: Cretaceous–Paleogene extinction event

text: Numerous species of benthic foraminifera became extinct during the event, presumably because they depend on organic debris for nutrients, while biomass in the ocean is thought to have decreased. As the marine microbiota recovered, it is thought that increased speciation of benthic foraminifera resulted from the increase in food sources. Phytoplankton recovery in the early Paleocene provided the food source to support large benthic foraminiferal assemblages, which are mainly detritus-feeding. Ultimate recovery of the benthic populations occurred over several stages lasting several hundred thousand years into the early Paleocene.


title: Cretaceous–Paleogene extinction event

text: There is significant variation in the fossil record as to the extinction rate of marine invertebrates across the K–Pg boundary. The apparent rate is influenced by a lack of fossil records, rather than extinctions.


title: Cretaceous–Paleogene extinction event

text: Ostracods, a class of small crustaceans that were prevalent in the upper Maastrichtian, left fossil deposits in a variety of locations. A review of these fossils shows that ostracod diversity was lower in the Paleocene than any other time in the Cenozoic. Current research cannot ascertain whether the extinctions occurred prior to, or during, the boundary interval.


title: Cretaceous–Paleogene extinction event

text: Approximately 60% of late-Cretaceous Scleractinia coral genera failed to cross the K–Pg boundary into the Paleocene. Further analysis of the coral extinctions shows that approximately 98% of colonial species, ones that inhabit warm, shallow tropical waters, became extinct. The solitary corals, which generally do not form reefs and inhabit colder and deeper (below the photic zone) areas of the ocean were less impacted by the K–Pg boundary. Colonial coral species rely upon symbiosis with photosynthetic algae, which collapsed due to the events surrounding the K–Pg boundary, but the use of data from coral fossils to support K–Pg extinction and subsequent Paleocene recovery, must be weighed against the changes that occurred in coral ecosystems through the K–Pg boundary.


title: Cretaceous–Paleogene extinction event

text: The numbers of cephalopod, echinoderm, and bivalve genera exhibited significant diminution after the K–Pg boundary. Most species of brachiopods, a small phylum of marine invertebrates, survived the K–Pg extinction event and diversified during the early Paleocene.


title: Cretaceous–Paleogene extinction event

text: Except for nautiloids (represented by the modern order Nautilida) and coleoids (which had already diverged into modern octopodes, squids, and cuttlefish) all other species of the molluscan class Cephalopoda became extinct at the K–Pg boundary. These included the ecologically significant belemnoids, as well as the ammonoids, a group of highly diverse, numerous, and widely distributed shelled cephalopods. Researchers have pointed out that the reproductive strategy of the surviving nautiloids, which rely upon few and larger eggs, played a role in outsurviving their ammonoid counterparts through the extinction event. The ammonoids utilized a planktonic strategy of reproduction (numerous eggs and planktonic larvae), which would have been devastated by the K–Pg extinction event. Additional research has shown that subsequent to this elimination of ammonoids from the global biota, nautiloids began an evolutionary radiation into shell shapes and complexities theretofore known only from ammonoids.


title: Cretaceous–Paleogene extinction event

text: Approximately 35% of echinoderm genera became extinct at the K–Pg boundary, although taxa that thrived in low-latitude, shallow-water environments during the late Cretaceous had the highest extinction rate. Mid-latitude, deep-water echinoderms were much less affected at the K–Pg boundary. The pattern of extinction points to habitat loss, specifically the drowning of carbonate platforms, the shallow-water reefs in existence at that time, by the extinction event.


title: Cretaceous–Paleogene extinction event

text: Other invertebrate groups, including rudists (reef-building clams) and inoceramids (giant relatives of modern scallops), also became extinct at the K–Pg boundary.


title: Cretaceous–Paleogene extinction event

text: There are fossil records of jawed fishes across the K–Pg boundary, which provide good evidence of extinction patterns of these classes of marine vertebrates. While the deep-sea realm was able to remain seemingly unaffected, there was an equal loss between the open marine apex predators and the durophagous demersal feeders on the continental shelf. Within cartilaginous fish, approximately 7 out of the 41 families of neoselachians (modern sharks, skates, and rays) disappeared after this event and batoids (skates and rays) lost nearly all the identifiable species, while more than 90% of teleost fish (bony fish) families survived.


title: Cretaceous–Paleogene extinction event

text: In the Maastrichtian age, 28 shark families and 13 batoid families thrived, of which 25 and 9, respectively, survived the K–T boundary event. Forty-seven of all neoselachian genera cross the K–T boundary, with 85% being sharks. Batoids display with 15%, a comparably low survival rate.


title: Cretaceous–Paleogene extinction event

text: There is evidence of a mass extinction of bony fishes at a fossil site immediately above the K–Pg boundary layer on Seymour Island near Antarctica, apparently precipitated by the K–Pg extinction event; the marine and freshwater environments of fishes mitigated the environmental effects of the extinction event.


title: Cretaceous–Paleogene extinction event

text: Insect damage to the fossilized leaves of flowering plants from fourteen sites in North America was used as a proxy for insect diversity across the K–Pg boundary and analyzed to determine the rate of extinction. Researchers found that Cretaceous sites, prior to the extinction event, had rich plant and insect-feeding diversity. During the early Paleocene, flora were relatively diverse with little predation from insects, even 1.7 million years after the extinction event.


title: Cretaceous–Paleogene extinction event

text: There is overwhelming evidence of global disruption of plant communities at the K–Pg boundary. Extinctions are seen both in studies of fossil pollen, and fossil leaves. In North America, the data suggests massive devastation and mass extinction of plants at the K–Pg boundary sections, although there were substantial megafloral changes before the boundary. In North America, approximately 57% of plant species became extinct. In high southern hemisphere latitudes, such as New Zealand and Antarctica, the mass die-off of flora caused no significant turnover in species, but dramatic and short-term changes in the relative abundance of plant groups. In some regions, the Paleocene recovery of plants began with recolonizations by fern species, represented as a fern spike in the geologic record; this same pattern of fern recolonization was observed after the 1980 Mount St. Helens eruption.


title: Cretaceous–Paleogene extinction event

text: Due to the wholesale destruction of plants at the K–Pg boundary, there was a proliferation of saprotrophic organisms, such as fungi, that do not require photosynthesis and use nutrients from decaying vegetation. The dominance of fungal species lasted only a few years while the atmosphere cleared and plenty of organic matter to feed on was present. Once the atmosphere cleared, photosynthetic organisms, initially ferns and other ground-level plants, returned. Just two species of fern appear to have dominated the landscape for centuries after the event.


title: Cretaceous–Paleogene extinction event

text: Polyploidy appears to have enhanced the ability of flowering plants to survive the extinction, probably because the additional copies of the genome such plants possessed allowed them to more readily adapt to the rapidly changing environmental conditions that followed the impact.


title: Cretaceous–Paleogene extinction event

text: While it appears that many fungi were wiped out at the K-Pg boundary, it is worth noting that evidence has been found indicating that some fungal species thrived in the years after the extinction event. Microfossils from that period indicate a great increase in fungal spores, long before the resumption of plentiful fern spores in the recovery after the impact. Monoporisporites and hypha are almost exclusive microfossils for a short span during and after the iridium boundary. These saprophytes would not need sunlight, allowing them to survive during a period when the atmosphere was likely clogged with dust and sulfur aerosols.


title: Cretaceous–Paleogene extinction event

text: The proliferation of fungi has occurred after several extinction events, including the Permian–Triassic extinction event, the largest known mass extinction in Earth's history, with up to 96% of all species suffering extinction.


title: Cretaceous–Paleogene extinction event

text: There is limited evidence for extinction of amphibians at the K–Pg boundary. A study of fossil vertebrates across the K–Pg boundary in Montana concluded that no species of amphibian became extinct. Yet there are several species of Maastrichtian amphibian, not included as part of this study, which are unknown from the Paleocene. These include the frog "Theatonius lancensis" and the albanerpetontid "Albanerpeton galaktion"; therefore, some amphibians do seem to have become extinct at the boundary. The relatively low levels of extinction seen among amphibians probably reflect the low extinction rates seen in freshwater animals.


title: Cretaceous–Paleogene extinction event

text: More than 80% of Cretaceous turtle species passed through the K–Pg boundary. All six turtle families in existence at the end of the Cretaceous survived into the Paleogene and are represented by living species.


title: Cretaceous–Paleogene extinction event

text: The living non-archosaurian reptile taxa, lepidosaurians (snakes, lizards and tuataras), survived across the K–Pg boundary.


title: Cretaceous–Paleogene extinction event

text: The rhynchocephalians were a widespread and relatively successful group of lepidosaurians during the early Mesozoic, but began to decline by the mid-Cretaceous, although they were very successful in South America. They are represented today by a single genus (the Tuatara), located exclusively in New Zealand.


title: Cretaceous–Paleogene extinction event

text: The order Squamata, which is represented today by lizards, snakes and amphisbaenians (worm lizards), radiated into various ecological niches during the Jurassic and was successful throughout the Cretaceous. They survived through the K–Pg boundary and are currently the most successful and diverse group of living reptiles, with more than 6,000 extant species. Many families of terrestrial squamates became extinct at the boundary, such as monstersaurians and polyglyphanodonts, and fossil evidence indicates they suffered very heavy losses in the K–Pg event, only recovering 10 million years after it.


title: Cretaceous–Paleogene extinction event

text: Giant non-archosaurian aquatic reptiles such as mosasaurs and plesiosaurs, which were the top marine predators of their time, became extinct by the end of the Cretaceous. The ichthyosaurs had disappeared from fossil records before the mass extinction occurred.


title: Cretaceous–Paleogene extinction event

text: The archosaur clade includes two surviving groups, crocodilians and birds, along with the various extinct groups of non-avian dinosaurs and pterosaurs.


title: Cretaceous–Paleogene extinction event

text: Ten families of crocodilians or their close relatives are represented in the Maastrichtian fossil records, of which five died out prior to the K–Pg boundary. Five families have both Maastrichtian and Paleocene fossil representatives. All of the surviving families of crocodyliforms inhabited freshwater and terrestrial environments—except for the Dyrosauridae, which lived in freshwater and marine locations. Approximately 50% of crocodyliform representatives survived across the K–Pg boundary, the only apparent trend being that no large crocodiles survived. Crocodyliform survivability across the boundary may have resulted from their aquatic niche and ability to burrow, which reduced susceptibility to negative environmental effects at the boundary. Jouve and colleagues suggested in 2008 that juvenile marine crocodyliforms lived in freshwater environments as do modern marine crocodile juveniles, which would have helped them survive where other marine reptiles became extinct; freshwater environments were not so strongly affected by the K–Pg extinction event as marine environments were.


title: Cretaceous–Paleogene extinction event

text: Two families of pterosaurs, Azhdarchidae and Nyctosauridae, were definitely present in the Maastrichtian, and they likely became extinct at the K–Pg boundary. Several other pterosaur lineages may have been present during the Maastrichtian, such as the ornithocheirids, pteranodontids, nyctosaurids, a possible tapejarid, a possible thalassodromid and a basal toothed taxon of uncertain affinities, though they are represented by fragmentary remains that are difficult to assign to any given group. While this was occurring, modern birds were undergoing diversification; traditionally it was thought that they replaced archaic birds and pterosaur groups, possibly due to direct competition, or they simply filled empty niches, but there is no correlation between pterosaur and avian diversities that are conclusive to a competition hypothesis, and small pterosaurs were present in the Late Cretaceous. At least some niches previously held by birds were reclaimed by pterosaurs prior to the K–Pg event.


title: Cretaceous–Paleogene extinction event

text: Most paleontologists regard birds as the only surviving dinosaurs (see Origin of birds). It is thought that all non-avian theropods became extinct, including then-flourishing groups such as enantiornithines and hesperornithiforms. Several analyses of bird fossils show divergence of species prior to the K–Pg boundary, and that duck, chicken, and ratite bird relatives coexisted with non-avian dinosaurs. Large collections of bird fossils representing a range of different species provides definitive evidence for the persistence of archaic birds to within 300,000 years of the K–Pg boundary. The absence of these birds in the Paleogene is evidence that a mass extinction of archaic birds took place there.


title: Cretaceous–Paleogene extinction event

text: The most successful and dominant group of avialans, enantiornithes, were wiped out. Only a small fraction of ground and water-dwelling Cretaceous bird species survived the impact, giving rise to today's birds. The only bird group known for certain to have survived the K–Pg boundary is the Aves. Avians may have been able to survive the extinction as a result of their abilities to dive, swim, or seek shelter in water and marshlands. Many species of avians can build burrows, or nest in tree holes, or termite nests, all of which provided shelter from the environmental effects at the K–Pg boundary. Long-term survival past the boundary was assured as a result of filling ecological niches left empty by extinction of non-avian dinosaurs. The open niche space and relative scarcity of predators following the K-Pg extinction allowed for adaptive radiation of various avian groups. Ratites, for example, rapidly diversified in the early Paleogene and are believed to have convergently developed flightlessness at least three to six times, often fulfilling the niche space for large herbivores once occupied by non-avian dinosaurs.


title: Cretaceous–Paleogene extinction event

text: Excluding a few controversial claims, scientists agree that all non-avian dinosaurs became extinct at the K–Pg boundary. The dinosaur fossil record has been interpreted to show both a decline in diversity and no decline in diversity during the last few million years of the Cretaceous, and it may be that the quality of the dinosaur fossil record is simply not good enough to permit researchers to distinguish between the options. There is no evidence that late Maastrichtian non-avian dinosaurs could burrow, swim, or dive, which suggests they were unable to shelter themselves from the worst parts of any environmental stress that occurred at the K–Pg boundary. It is possible that small dinosaurs (other than birds) did survive, but they would have been deprived of food, as herbivorous dinosaurs would have found plant material scarce and carnivores would have quickly found prey in short supply.


title: Cretaceous–Paleogene extinction event

text: The growing consensus about the endothermy of dinosaurs (see dinosaur physiology) helps to understand their full extinction in contrast with their close relatives, the crocodilians. Ectothermic ("cold-blooded") crocodiles have very limited needs for food (they can survive several months without eating), while endothermic ("warm-blooded") animals of similar size need much more food to sustain their faster metabolism. Thus, under the circumstances of food chain disruption previously mentioned, non-avian dinosaurs died out, while some crocodiles survived. In this context, the survival of other endothermic animals, such as some birds and mammals, could be due, among other reasons, to their smaller needs for food, related to their small size at the extinction epoch.


title: Cretaceous–Paleogene extinction event

text: Whether the extinction occurred gradually or suddenly has been debated, as both views have support from the fossil record. A study of 29 fossil sites in Catalan Pyrenees of Europe in 2010 supports the view that dinosaurs there had great diversity until the asteroid impact, with more than 100 living species. More recent research indicates that this figure is obscured by taphonomic biases and the sparsity of the continental fossil record. The results of this study, which were based on estimated real global biodiversity, showed that between 628 and 1,078 non-avian dinosaur species were alive at the end of the Cretaceous and underwent sudden extinction after the Cretaceous–Paleogene extinction event. Alternatively, interpretation based on the fossil-bearing rocks along the Red Deer River in Alberta, Canada, supports the gradual extinction of non-avian dinosaurs; during the last 10 million years of the Cretaceous layers there, the number of dinosaur species seems to have decreased from about 45 to approximately 12. Other scientists have made the same assessment following their research.


title: Cretaceous–Paleogene extinction event

text: Several researchers support the existence of Paleocene non-avian dinosaurs. Evidence of this existence is based on the discovery of dinosaur remains in the Hell Creek Formation up to above and 40,000 years later than the K–Pg boundary. Pollen samples recovered near a fossilized hadrosaur femur recovered in the Ojo Alamo Sandstone at the San Juan River in Colorado, indicate that the animal lived during the Cenozoic, approximately (about 1 million years after the K–Pg extinction event). If their existence past the K–Pg boundary can be confirmed, these hadrosaurids would be considered a dead clade walking. The scientific consensus is that these fossils were eroded from their original locations and then re-buried in much later sediments (also known as reworked fossils).


title: Cretaceous–Paleogene extinction event

text: The choristoderes (semi-aquatic archosauromorphs) survived across the K–Pg boundary but would die out in the early Miocene. Studies on "Champsosaurus" palatal teeth suggest that there were dietary changes among the various species across the K–Pg event.


title: Cretaceous–Paleogene extinction event

text: All major Cretaceous mammalian lineages, including monotremes (egg-laying mammals), multituberculates, metatherians, eutherians, dryolestoideans, and gondwanatheres survived the K–Pg extinction event, although they suffered losses. In particular, metatherians largely disappeared from North America, and the Asian deltatheroidans became extinct (aside from the lineage leading to "Gurbanodelta"). In the Hell Creek beds of North America, at least half of the ten known multituberculate species and all eleven metatherians species are not found above the boundary. Multituberculates in Europe and North America survived relatively unscathed and quickly bounced back in the Paleocene, but Asian forms were devastated, never again to represent a significant component of mammalian fauna. A recent study indicates that metatherians suffered the heaviest losses at the K–Pg event, followed by multituberculates, while eutherians recovered the quickest.


title: Cretaceous–Paleogene extinction event

text: Mammalian species began diversifying approximately 30 million years prior to the K–Pg boundary. Diversification of mammals stalled across the boundary.


title: Cretaceous–Paleogene extinction event

text: Current research indicates that mammals did not explosively diversify across the K–Pg boundary, despite the ecological niches made available by the extinction of dinosaurs. Several mammalian orders have been interpreted as diversifying immediately after the K–Pg boundary, including Chiroptera (bats) and Cetartiodactyla (a diverse group that today includes whales and dolphins and even-toed ungulates), although recent research concludes that only marsupial orders diversified soon after the K–Pg boundary.


title: Cretaceous–Paleogene extinction event

text: K–Pg boundary mammalian species were generally small, comparable in size to rats; this small size would have helped them find shelter in protected environments. It is postulated that some early monotremes, marsupials, and placentals were semiaquatic or burrowing, as there are multiple mammalian lineages with such habits today. Any burrowing or semiaquatic mammal would have had additional protection from K–Pg boundary environmental stresses.


title: Cretaceous–Paleogene extinction event

text: In North American terrestrial sequences, the extinction event is best represented by the marked discrepancy between the rich and relatively abundant late-Maastrichtian pollen record and the post-boundary fern spike. A highly informative sequence of dinosaur-bearing rocks from the K–Pg boundary is found in western North America, particularly the late Maastrichtian-age Hell Creek Formation of Montana. Comparison with the older Judith River Formation (Montana) and Dinosaur Park Formation (Alberta), which both date from approximately 75 Ma, provides information on the changes in dinosaur populations over the last 10 million years of the Cretaceous. These fossil beds are geographically limited, covering only part of one continent.


title: Cretaceous–Paleogene extinction event

text: The middle–late Campanian formations show a greater diversity of dinosaurs than any other single group of rocks. The late Maastrichtian rocks contain the largest members of several major clades: "Tyrannosaurus", "Ankylosaurus", "Pachycephalosaurus", "Triceratops", and "Torosaurus", which suggests food was plentiful immediately prior to the extinction.


title: Cretaceous–Paleogene extinction event

text: Plant fossils illustrate the reduction in plant species across the K–Pg boundary. In the sediments below the K–Pg boundary the dominant plant remains are angiosperm pollen grains, but the boundary layer contains little pollen and is dominated by fern spores. More usual pollen levels gradually resume above the boundary layer. This is reminiscent of areas blighted by modern volcanic eruptions, where the recovery is led by ferns, which are later replaced by larger angiosperm plants. A study of ossilized fish bones found at Tanis in North Dakota suggests that the Cretaceous-Paleogene mass extinction happened during the Northern Hemisphere spring.


title: Cretaceous–Paleogene extinction event

text: The mass extinction of marine plankton appears to have been abrupt and right at the K–Pg boundary. Ammonite genera became extinct at or near the K–Pg boundary; there was a smaller and slower extinction of ammonite genera prior to the boundary associated with a late Cretaceous marine regression. The gradual extinction of most inoceramid bivalves began well before the K–Pg boundary, and a small, gradual reduction in ammonite diversity occurred throughout the very late Cretaceous.


title: Cretaceous–Paleogene extinction event

text: Further analysis shows that several processes were in progress in the late Cretaceous seas and partially overlapped in time, then ended with the abrupt mass extinction. The diversity of marine life decreased when the climate near the K–Pg boundary increased in temperature. The temperature increased about three to four degrees very rapidly between 65.4 and 65.2 million years ago, which is very near the time of the extinction event. Not only did the climate temperature increase, but the water temperature decreased, causing a drastic decrease in marine diversity.


title: Cretaceous–Paleogene extinction event

text: The scientific consensus is that the asteroid impact at the K–Pg boundary left megatsunami deposits and sediments around the area of the Caribbean Sea and Gulf of Mexico, from the colossal waves created by the impact. These deposits have been identified in the La Popa basin in northeastern Mexico, platform carbonates in northeastern Brazil, in Atlantic deep-sea sediments, and in the form of the thickest-known layer of graded sand deposits, around , in the Chicxulub crater itself, directly above the shocked granite ejecta. The megatsunami has been estimated at more than tall, as the asteroid fell into relatively shallow seas; in deep seas it would have been tall.


title: Cretaceous–Paleogene extinction event

text: Fossiliferous sedimentary rocks deposited during the K–Pg impact have been found in the Gulf of Mexico area, including tsunami wash deposits carrying remains of a mangrove-type ecosystem, evidence that after the impact water sloshed back and forth repeatedly in the Gulf of Mexico, and dead fish left in shallow water but not disturbed by scavengers.


title: Cretaceous–Paleogene extinction event

text: The rapidity of the extinction is a controversial issue, because some theories about its causes imply a rapid extinction over a relatively short period (from a few years to a few thousand years), while others imply longer periods. The issue is difficult to resolve because of the Signor–Lipps effect, where the fossil record is so incomplete that most extinct species probably died out long after the most recent fossil that has been found. Scientists have also found very few continuous beds of fossil-bearing rock that cover a time range from several million years before the K–Pg extinction to several million years after it.


title: Cretaceous–Paleogene extinction event

text: The sedimentation rate and thickness of K–Pg clay from three sites suggest rapid extinction, perhaps over a period of less than 10,000 years. At one site in the Denver Basin of Colorado, after the K–Pg boundary layer was deposited, the fern spike lasted approximately 1,000 years, and no more than 71,000 years; at the same location, the earliest appearance of Cenozoic mammals occurred after approximately 185,000 years, and no more than 570,000 years, "indicating rapid rates of biotic extinction and initial recovery in the Denver Basin during this event." Models presented at the annual meeting of the American Geophysical Union demonstrated that the period of global darkness following the Chicxulub impact would have persisted in the Hell Creek Formation nearly 2 years.


title: Cretaceous–Paleogene extinction event

text: In 1980, a team of researchers consisting of Nobel Prize-winning physicist Luis Alvarez, his son, geologist Walter Alvarez, and chemists Frank Asaro and Helen Michel discovered that sedimentary layers found all over the world at the Cretaceous–Paleogene boundary contain a concentration of iridium many times greater than normal (30, 160, and 20 times in three sections originally studied). Iridium is extremely rare in Earth's crust because it is a siderophile element which mostly sank along with iron into Earth's core during planetary differentiation. As iridium remains more abundant in most asteroids and comets, the Alvarez team suggested that an asteroid struck the Earth at the time of the K–Pg boundary. There were earlier speculations on the possibility of an impact event, but this was the first hard evidence.


title: Cretaceous–Paleogene extinction event

text: This hypothesis was viewed as radical when first proposed, but additional evidence soon emerged. The boundary clay was found to be full of minute spherules of rock, crystallized from droplets of molten rock formed by the impact. Shocked quartz and other minerals were also identified in the K–Pg boundary. The identification of giant tsunami beds along the Gulf Coast and the Caribbean provided more evidence, and suggested that the impact may have occurred nearby—as did the discovery that the K–Pg boundary became thicker in the southern United States, with meter-thick beds of debris occurring in northern New Mexico.


title: Cretaceous–Paleogene extinction event

text: Further research identified the giant Chicxulub crater, buried under Chicxulub on the coast of Yucatán, as the source of the K–Pg boundary clay. Identified in 1990 based on work by geophysicist Glen Penfield in 1978, the crater is oval, with an average diameter of roughly , about the size calculated by the Alvarez team.


title: Cretaceous–Paleogene extinction event

text: In a 2013 paper, Paul Renne of the Berkeley Geochronology Center dated the impact at years ago, based on argon–argon dating. He further posits that the mass extinction occurred within 32,000 years of this date.


title: Cretaceous–Paleogene extinction event

text: In 2007, it was proposed that the impactor belonged to the Baptistina family of asteroids. This link has been doubted, though not disproved, in part because of a lack of observations of the asteroid and its family. It was reported in 2009 that 298 Baptistina does not share the chemical signature of the K–Pg impactor. Further, a 2011 Wide-field Infrared Survey Explorer (WISE) study of reflected light from the asteroids of the family estimated their break-up at 80 Ma, giving them insufficient time to shift orbits and impact Earth by 66 Ma.


title: Cretaceous–Paleogene extinction event

text: Additional evidence for the impact event is found at the Tanis site in southwestern North Dakota, United States. Tanis is part of the heavily studied Hell Creek Formation, a group of rocks spanning four states in North America renowned for many significant fossil discoveries from the Upper Cretaceous and lower Paleocene. Tanis is an extraordinary and unique site because it appears to record the events from the first minutes until a few hours after the impact of the giant Chicxulub asteroid in extreme detail. Amber from the site has been reported to contain microtektites matching those of the Chicxulub impact event. Some researchers question the interpretation of the findings at the site or are skeptical of the team leader, Robert DePalma, who had not yet received his Ph.D. in geology at the time of the discovery and whose commercial activities have been regarded with suspicion.


title: Cretaceous–Paleogene extinction event

text: In March 2010, an international panel of 41 scientists reviewed 20 years of scientific literature and endorsed the asteroid hypothesis, specifically the Chicxulub impact, as the cause of the extinction, ruling out other theories such as massive volcanism. They had determined that a asteroid hurtled into Earth at Chicxulub on Mexico's Yucatán Peninsula. The collision would have released the same energy as —more than a billion times the energy of the atomic bombings of Hiroshima and Nagasaki. The Chicxulub impact caused a global catastrophe. Some of the phenomena were brief occurrences immediately following the impact, but there were also long-term geochemical and climatic disruptions that devastated the ecology.


title: Cretaceous–Paleogene extinction event

text: The re-entry of ejecta into Earth's atmosphere included a brief (hours-long) but intense pulse of infrared radiation, cooking exposed organisms. This is debated, with opponents arguing that local ferocious fires, probably limited to North America, fall short of global firestorms. This is the "Cretaceous–Paleogene firestorm debate". A paper in 2013 by a prominent modeler of nuclear winter suggested that, based on the amount of soot in the global debris layer, the entire terrestrial biosphere might have burned, implying a global soot-cloud blocking out the sun and creating an impact winter effect. If widespread fires occurred this would have exterminated the most vulnerable organisms that survived the period immediately after the impact.


title: Cretaceous–Paleogene extinction event

text: Aside from the hypothesized fire and/or impact winter effects, the impact would have created a dust cloud that blocked sunlight for up to a year, inhibiting photosynthesis. Freezing temperatures probably lasted for at least three years. At Brazos section, the sea surface temperature dropped as much as for decades after the impact. It would take at least ten years for such aerosols to dissipate, and would account for the extinction of plants and phytoplankton, and subsequently herbivores and their predators. Creatures whose food chains were based on detritus would have a reasonable chance of survival.


title: Cretaceous–Paleogene extinction event

text: The asteroid hit an area of carbonate rock containing a large amount of combustible hydrocarbons and sulphur, much of which was vaporized, thereby injecting sulfuric acid aerosols into the stratosphere, which might have reduced sunlight reaching the Earth's surface by more than 50%, and would have caused acid rain. The resulting acidification of the oceans would kill many organisms that grow shells of calcium carbonate. According to models of the Hell Creek Formation, the onset of global darkness would have reached its maximum in only a few weeks and likely lasted upwards of 2 years.


title: Cretaceous–Paleogene extinction event

text: Beyond extinction impacts, the event also caused more general changes of flora and fauna such as giving rise to neotropical rainforest biomes like the Amazonia, replacing species composition and structure of local forests during ~6 million years of recovery to former levels of plant diversity.<ref name="10.1126/science.abf1969"></ref>


title: Cretaceous–Paleogene extinction event

text: In 2016, a scientific drilling project obtained deep rock-core samples from the peak ring around the Chicxulub impact crater. The discoveries confirmed that the rock comprising the peak ring had been shocked by immense pressure and melted in just minutes from its usual state into its present form. Unlike sea-floor deposits, the peak ring was made of granite originating much deeper in the earth, which had been ejected to the surface by the impact. Gypsum is a sulfate-containing rock usually present in the shallow seabed of the region; it had been almost entirely removed, vaporized into the atmosphere. Further, the event was immediately followed by a megatsunami sufficient to lay down the largest known layer of sand separated by grain size directly above the peak ring. The impactor was large enough to create a peak ring, to melt, shock, and eject deep granite, to create colossal water movements, and to eject an immense quantity of vaporized rock and sulfates into the atmosphere, where they would have persisted for several years. This worldwide dispersal of dust and sulfates would have affected climate catastrophically, led to large temperature drops, and devastated the food chain.


title: Cretaceous–Paleogene extinction event

text: Although the concurrence of the end-Cretaceous extinctions with the Chicxulub asteroid impact strongly supports the impact hypothesis, some scientists continue to support other contributing causes: volcanic eruptions, climate change, sea level change, and other impact events. The end-Cretaceous event is the only mass extinction known to be associated with an impact, and other large impacts, such as the Manicouagan Reservoir impact, do not coincide with any noticeable extinction events.


title: Cretaceous–Paleogene extinction event

text: Before 2000, arguments that the Deccan Traps flood basalts caused the extinction were usually linked to the view that the extinction was gradual, as the flood basalt events were thought to have started around 68 Mya and lasted more than 2 million years. The most recent evidence shows that the traps erupted over a period of only 800,000 years spanning the K–Pg boundary, and therefore may be responsible for the extinction and the delayed biotic recovery thereafter.


title: Cretaceous–Paleogene extinction event

text: The Deccan Traps could have caused extinction through several mechanisms, including the release of dust and sulfuric aerosols into the air, which might have blocked sunlight and thereby reduced photosynthesis in plants. In addition, Deccan Trap volcanism might have resulted in carbon dioxide emissions that increased the greenhouse effect when the dust and aerosols cleared from the atmosphere. The increased carbon dioxide emissions also caused acid rain, evidenced by increased mercury deposition due to increased solubility of mercury compounds in more acidic water.


title: Cretaceous–Paleogene extinction event

text: In the years when the Deccan Traps hypothesis was linked to a slower extinction, Luis Alvarez (d. 1988) replied that paleontologists were being misled by sparse data. While his assertion was not initially well-received, later intensive field studies of fossil beds lent weight to his claim. Eventually, most paleontologists began to accept the idea that the mass extinctions at the end of the Cretaceous were largely or at least partly due to a massive Earth impact. Even Walter Alvarez acknowledged that other major changes may have contributed to the extinctions.


title: Cretaceous–Paleogene extinction event

text: Combining these theories, some geophysical models suggest that the impact contributed to the Deccan Traps.


title: Cretaceous–Paleogene extinction event

text: These models, combined with high-precision radiometric dating, suggest that the Chicxulub impact could have triggered some of the largest Deccan eruptions, as well as eruptions at active volcanoes anywhere on Earth.


title: Cretaceous–Paleogene extinction event

text: Other crater-like topographic features have also been proposed as impact craters formed in connection with Cretaceous–Paleogene extinction. This suggests the possibility of near-simultaneous multiple impacts, perhaps from a fragmented asteroidal object similar to the Shoemaker–Levy 9 impact with Jupiter. In addition to the Chicxulub crater, there is the Boltysh crater in Ukraine (), the Silverpit crater in the North Sea () possibly formed by bolide impact, and the controversial and much larger Shiva crater. Any other craters that might have formed in the Tethys Ocean would since have been obscured by the northward tectonic drift of Africa and India.


title: Cretaceous–Paleogene extinction event

text: There is clear evidence that sea levels fell in the final stage of the Cretaceous by more than at any other time in the Mesozoic era. In some Maastrichtian stage rock layers from various parts of the world, the later layers are terrestrial; earlier layers represent shorelines and the earliest layers represent seabeds. These layers do not show the tilting and distortion associated with mountain building, therefore the likeliest explanation is a "regression", a drop in sea level. There is no direct evidence for the cause of the regression, but the currently accepted explanation is that the mid-ocean ridges became less active and sank under their own weight.


title: Cretaceous–Paleogene extinction event

text: A severe regression would have greatly reduced the continental shelf area, the most species-rich part of the sea, and therefore could have been enough to cause a marine mass extinction, but this change would not have caused the extinction of the ammonites. The regression would also have caused climate changes, partly by disrupting winds and ocean currents and partly by reducing the Earth's albedo and increasing global temperatures.


title: Cretaceous–Paleogene extinction event

text: Marine regression also resulted in the loss of epeiric seas, such as the Western Interior Seaway of North America. The loss of these seas greatly altered habitats, removing coastal plains that ten million years before had been host to diverse communities such as are found in rocks of the Dinosaur Park Formation. Another consequence was an expansion of freshwater environments, since continental runoff now had longer distances to travel before reaching oceans. While this change was favorable to freshwater vertebrates, those that prefer marine environments, such as sharks, suffered.


title: Cretaceous–Paleogene extinction event

text: Proponents of multiple causation view the suggested single causes as either too small to produce the vast scale of the extinction, or not likely to produce its observed taxonomic pattern. In a review article, J. David Archibald and David E. Fastovsky discussed a scenario combining three major postulated causes: volcanism, marine regression, and extraterrestrial impact. In this scenario, terrestrial and marine communities were stressed by the changes in, and loss of, habitats. Dinosaurs, as the largest vertebrates, were the first affected by environmental changes, and their diversity declined. At the same time, particulate materials from volcanism cooled and dried areas of the globe. Then an impact event occurred, causing collapses in photosynthesis-based food chains, both in the already-stressed terrestrial food chains and in the marine food chains.


title: Cretaceous–Paleogene extinction event

text: Based on studies at Seymour Island in Antarctica, Sierra Petersen and colleagues argue that there were two separate extinction events near the Cretaceous–Paleogene boundary, with one correlating to Deccan Trap volcanism and one correlated with the Chicxulub impact. The team analyzed combined extinction patterns using a new clumped isotope temperature record from a hiatus-free, expanded K–Pg boundary section. They documented a 7.8±3.3 °C warming synchronous with the onset of Deccan Traps volcanism and a second, smaller warming at the time of meteorite impact. They suggest local warming may have been amplified due to the simultaneous disappearance of continental or sea ice. Intra-shell variability indicates a possible reduction in seasonality after Deccan eruptions began, continuing through the meteorite event. Species extinction at Seymour Island occurred in two pulses that coincide with the two observed warming events, directly linking the end-Cretaceous extinction at this site to both volcanic and meteorite events via climate change.


title: Cretaceous–Paleogene extinction event

text: The K–Pg extinction had a profound effect on the evolution of life on Earth. The elimination of dominant Cretaceous groups allowed other organisms to take their place, causing a remarkable amount of species diversification during the Paleogene Period. The most striking example is the replacement of dinosaurs by mammals. After the K–Pg extinction, mammals evolved rapidly to fill the niches left vacant by the dinosaurs. Also significant, within the mammalian genera, new species were approximately 9.1% larger after the K–Pg boundary.


title: Cretaceous–Paleogene extinction event

text: Other groups also substantially diversified. Based on molecular sequencing and fossil dating, many species of birds (the Neoaves group in particular) appeared to radiate after the K–Pg boundary. They even produced giant, flightless forms, such as the herbivorous "Gastornis" and Dromornithidae, and the predatory Phorusrhacidae. The extinction of Cretaceous lizards and snakes may have led to the evolution of modern groups such as iguanas, monitor lizards, and boas. On land, giant boid and enormous madtsoiid snakes appeared, and in the seas, giant sea snakes evolved. Teleost fish diversified explosively, filling the niches left vacant by the extinction. Groups appearing in the Paleocene and Eocene epochs include billfish, tunas, eels, and flatfish. Major changes are also seen in Paleogene insect communities. Many groups of ants were present in the Cretaceous, but in the Eocene ants became dominant and diverse, with larger colonies. Butterflies diversified as well, perhaps to take the place of leaf-eating insects wiped out by the extinction. The advanced mound-building termites, Termitidae, also appear to have risen in importance.


title: Cretaceous–Paleogene extinction event

text: It is thought that body sizes of placental mammalian survivors evolutionarily increased first, allowing them to fill niches after the extinctions, with brain sizes increasing later in the Eocene.


title: Disco

text: Disco is a genre of dance music and a subculture that emerged in the 1970s from the United States' urban nightlife scene. Its sound is typified by four-on-the-floor beats, syncopated basslines, string sections, horns, electric piano, synthesizers, and electric rhythm guitars.


title: Disco

text: Disco started as a mixture of music from venues popular with Italian Americans, Hispanic and Latino Americans and Black Americans in Philadelphia and New York City during the late 1960s and early 1970s. Disco can be seen as a reaction by the 1960s counterculture to both the dominance of rock music and the stigmatization of dance music at the time. Several dance styles were developed during the period of disco's popularity in the United States, including "the Bump" and "the Hustle".


title: Disco

text: In the course of the 1970s, disco music was developed further mainly by artists from the United States and Europe. Well-known artists include: ABBA, the Bee Gees, Donna Summer, Gloria Gaynor, Giorgio Moroder, Baccara, Boney M., Earth Wind & Fire, Chaka Khan, Chic, KC and the Sunshine Band, Thelma Houston, Sister Sledge, Sylvester, The Trammps and the Village People. While performers garnered public attention, record producers working behind the scenes played an important role in developing the genre. By the late 1970s, most major U.S. cities had thriving disco club scenes, and DJs would mix dance records at clubs such as Studio 54 in Manhattan, a venue popular among celebrities. Nightclub-goers often wore expensive, extravagant outfits, consisting predominantly of loose, flowing pants or dresses for ease of movement while dancing. There was also a thriving drug subculture in the disco scene, particularly for drugs that would enhance the experience of dancing to the loud music and the flashing lights, such as cocaine and quaaludes, the latter being so common in disco subculture that they were nicknamed "disco biscuits". Disco clubs were also associated with promiscuity as a reflection of the sexual revolution of this era in popular history. Films such as "Saturday Night Fever" (1977) and "Thank God It's Friday" (1978) contributed to disco's mainstream popularity.


title: Disco

text: Disco declined as a major trend in popular music in the United States following the infamous Disco Demolition Night, and it continued to sharply decline in popularity in the U.S. during the early 1980s; however, it remained popular in Italy and some European countries throughout the 1980s, and during this time also started becoming trendy in places elsewhere including India and the Middle East, where they were blended with regional folk styles such as "ghazals" and belly dancing. Disco would eventually become a key influence in the development of electronic dance music, house music, hip hop, new wave, dance-punk, and post-disco. The style has had several newer scenes since the 1990s, and the influence of disco remains strong across American and European pop music. A revival has been underway since the early 2010s, coming to great popularity in the early 2020s. Albums that have contributed to this revival include "Confessions On A Dance Floor", "Random Access Memories", "The Slow Rush", "Cuz I Love You", "Future Nostalgia", "Hey U X", "Melodrama", "What's Your Pleasure?", "About Last Night...", "Róisín Machine", and Kylie Minogue's album itself titled "Disco".


title: Disco

text: The term "disco" is shorthand for the word "discothèque", a French word for "library of phonograph records" derived from "bibliothèque". The word "discothèque" had the same meaning in English in the 1950s.


title: Disco

text: "Discothèque" became used in French for a type of nightclub in Paris, France, after these had resorted to playing records during the Nazi occupation in the early 1940s. Some clubs used it as their proper name. In 1960, it was also used to describe a Parisian nightclub in an English magazine.


title: Disco

text: In the summer of 1964, a short sleeveless dress called "discotheque dress" was briefly very popular in the United States. The earliest known use for the abbreviated form "disco" described this dress and has been found in "The Salt Lake Tribune" on July 12, 1964, "Playboy" magazine used it in September of the same year to describe Los Angeles nightclubs.


title: Disco

text: Vince Aletti was one of the first to describe disco as a sound or a music genre. He wrote the feature article "Discotheque Rock Paaaaarty" that appeared in "Rolling Stone" magazine in September 1973.


title: Disco

text: The music typically layered soaring, often-reverberated vocals, often doubled by horns, over a background "pad" of electric pianos and "chicken-scratch" rhythm guitars played on an electric guitar. Lead guitar features less frequently in disco than in rock. "The "rooster scratch" sound is achieved by lightly pressing the guitar strings against the fretboard and then quickly releasing them just enough to get a slightly muted poker [sound] while constantly strumming very close to the bridge." Other backing keyboard instruments include the piano, electric organ (during early years), string synthesizers, and electromechanical keyboards such as the Fender Rhodes electric piano, Wurlitzer electric piano, and Hohner Clavinet. Donna Summer's 1977 song "I Feel Love", produced by Giorgio Moroder with a prominent Moog synthesizer on the beat, was one of the first disco tracks to use the synthesizer.


title: Disco

text: The rhythm is laid down by prominent, syncopated basslines (with heavy use of broken octaves, that is, octaves with the notes sounded one after the other) played on the bass guitar and by drummers using a drum kit, African/Latin percussion, and electronic drums such as Simmons and Roland drum modules. The sound was enriched with solo lines and harmony parts played by a variety of orchestral instruments, such as harp, violin, viola, cello, trumpet, saxophone, trombone, clarinet, flugelhorn, French horn, tuba, English horn, oboe, flute (sometimes especially the alto flute and occasionally bass flute), piccolo, timpani and synth strings, string section or a full string orchestra.


title: Disco

text: Most disco songs have a steady four-on-the-floor beat set by a bass drum, a quaver or semi-quaver hi-hat pattern with an open hissing hi-hat on the off-beat, and a heavy, syncopated bass line. A recording error in the 1975 song "Bad Luck" by Harold Melvin & the Blue Notes where Earl Young's hi-hat was too loud in the recording is said to have established loud hi-hats in disco. Other Latin rhythms such as the rhumba, the samba, and the cha-cha-cha are also found in disco recordings, and Latin polyrhythms, such as a rhumba beat layered over a merengue, are commonplace. The quaver pattern is often supported by other instruments such as the rhythm guitar and may be implied rather than explicitly present.


title: Disco

text: Songs often use syncopation, which is the accenting of unexpected beats. In general, the difference between disco, or any dance song, and a rock or popular song is that in dance music the bass drum hits "four to the floor", at least once a beat (which in 4/4 time is 4 beats per measure). Disco is further characterized by a 16th note division of the quarter notes as shown in the second drum pattern below, after a typical rock drum pattern.


title: Disco

text: The orchestral sound is usually known as "disco sound" relies heavily on string sections and horns playing linear phrases, in unison with the soaring, often reverberated vocals or playing instrumental fills, while electric pianos and chicken-scratch guitars create the background "pad" sound defining the harmony progression. Typically, all of the doubling of parts and use of additional instruments creates a rich "wall of sound". There are, however, more minimalist flavors of disco with reduced, transparent instrumentation.


title: Disco

text: Harmonically, disco music typically contains major and minor seven chords, which are found more often in jazz than pop music.


title: Disco

text: The "disco sound" was much more costly to produce than many of the other popular music genres from the 1970s. Unlike the simpler, four-piece-band sound of funk, soul music of the late 1960s, or the small jazz organ trios, disco music often included a large band, with several chordal instruments (guitar, keyboards, synthesizer), several drum or percussion instruments (drumkit, Latin percussion, electronic drums), a horn section, a string orchestra, and a variety of "classical" solo instruments (for example, flute, piccolo, and so on).


title: Disco

text: Disco songs were arranged and composed by experienced arrangers and orchestrators, and record producers added their creative touches to the overall sound using multitrack recording techniques and effects units. Recording complex arrangements with such a large number of instruments and sections required a team that included a conductor, copyists, record producers, and mixing engineers. Mixing engineers had an important role in the disco production process, because disco songs used as many as 64 tracks of vocals and instruments. Mixing engineers and record producers, under the direction of arrangers, compiled these tracks into a fluid composition of verses, bridges, and refrains, complete with builds and breaks. Mixing engineers and record producers helped to develop the "disco sound" by creating a distinctive-sounding, sophisticated disco mix.


title: Disco

text: Early records were the "standard" three-minute version until Tom Moulton came up with a way to make songs longer so that he could take a crowd of dancers at a club to another level and keep them dancing longer. He found that it was impossible to make the 45-RPM vinyl singles of the time longer, as they could usually hold no more than five minutes of good-quality music. With the help of José Rodriguez, his remaster/mastering engineer, he pressed a single on a 10" disc instead of 7". They cut the next single on a 12" disc, the same format as a standard album. Moulton and Rodriguez discovered that these larger records could have much longer songs and remixes. 12" single records, also known as "Maxi singles", quickly became the standard format for all DJs of the disco genre.


title: Disco

text: By the late 1970s most major US cities had thriving disco club scenes. The largest scenes were most notably in New York City but also in Philadelphia, San Francisco, Miami, and Washington, D.C. The scene was centered on discotheques, nightclubs, and private loft parties.


title: Disco

text: In the 1970s, notable discos included "Crisco Disco", "The Sanctuary", "Leviticus", "Studio 54" and "Paradise Garage" in New York, "Artemis" in Philadelphia, "Studio One" in Los Angeles, "Dugan's Bistro" in Chicago, and "The Library" in Atlanta.


title: Disco

text: In the late '70s, Studio 54 in Midtown Manhattan was arguably the best known nightclub in the world. This club played a major formative role in the growth of disco music and nightclub culture in general. It was operated by Steve Rubell and Ian Schrager and was notorious for the hedonism that went on within; the balconies were known for sexual encounters, and drug use was rampant. Its dance floor was decorated with an image of the "Man in the Moon" that included an animated cocaine spoon.


title: Disco

text: The "Copacabana", another New York nightclub dating to the 1940s, had a revival in the late 1970s when it embraced disco; it would become the setting of a Barry Manilow song of the same name.


title: Disco

text: In Washington, D.C., large disco clubs such as "The Pier" ("Pier 9") and "The Other Side," originally regarded exclusively as "gay bars", became particularly popular among the capital area's gay and straight college students in the late '70s.


title: Disco

text: By 1979 there were 15,000-20,000 disco nightclubs in the US, many of them opening in suburban shopping centers, hotels and restaurants. The 2001 Club franchises were the most prolific chain of disco clubs in the country. Although many other attempts were made to franchise disco clubs, 2001 was the only one to successfully do so in this time frame.


title: Disco

text: Powerful, bass-heavy, hi-fi sound systems were viewed as a key part of the disco club experience. "[Loft-party host David] Mancuso introduced the technologies of tweeter arrays (clusters of small loudspeakers, which emit high-end frequencies, positioned above the floor) and bass reinforcements (additional sets of subwoofers positioned at ground level) at the start of the 1970s to boost the treble and bass at opportune moments, and by the end of the decade sound engineers such as Richard Long had multiplied the effects of these innovations in venues such as the Garage."


title: Disco

text: Typical lighting designs for disco dance floors could include multi-coloured lights that swirl around or flash to the beat, strobe light, an illuminated dance floor and a mirror ball.


title: Disco

text: Disco-era disc jockeys (DJs) would often remix existing songs using reel-to-reel tape machines, and add in percussion breaks, new sections, and new sounds. DJs would select songs and grooves according to what the dancers wanted, transitioning from one song to another with a DJ mixer and using a microphone to introduce songs and speak to the audiences. Other equipment was added to the basic DJ setup, providing unique sound manipulations, such as reverb, equalization, and echo effects unit. Using this equipment, a DJ could do effects such as cutting out all but the bassline of a song and then slowly mixing in the beginning of another song using the DJ mixer's crossfader. Notable U.S. disco DJs include Francis Grasso of The Sanctuary, David Mancuso of The Loft, Frankie Knuckles of the Chicago Warehouse, Larry Levan of the Paradise Garage, Nicky Siano, Walter Gibbons, Karen Mixon Cook, Jim Burgess, John "Jellybean" Benitez, Richie Kulala of Studio 54 and Rick Salsalini.


title: Disco

text: Some DJs were also record producers who created and produced disco songs in the recording studio. Larry Levan, for example, was a prolific record producer as well as a DJ. Because record sales were often dependent on dance floor play by DJs in leading nightclubs, DJs were also influential for the development and popularization of certain types of disco music being produced for record labels.


title: Disco

text: In the early years, dancers in discos danced in a "hang loose" or "freestyle" approach. At first, many dancers improvised their own dance styles and dance steps. Later in the disco era, popular dance styles were developed, including the "Bump", "Penguin", "Boogaloo", "Watergate" and "Robot". By October 1975 the Hustle reigned. It was highly stylized, sophisticated and overtly sexual. Variations included the Brooklyn Hustle, New York Hustle and Latin Hustle.


title: Disco

text: During the disco era, many nightclubs would commonly host disco dance competitions or offer free dance lessons. Some cities had disco dance instructors or dance schools, which taught people how to do popular disco dances such as "touch dancing", "the hustle", and "the cha cha". The pioneer of disco dance instruction was Karen Lustgarten in San Francisco in 1973. Her book "The Complete Guide to Disco Dancing" (Warner Books 1978) was the first to name, break down and codify popular disco dances as dance forms and distinguish between disco freestyle, partner and line dances. The book topped the "New York Times" bestseller list for 13 weeks and was translated into Chinese, German and French.


title: Disco

text: In Chicago, the "Step By Step" disco dance TV show was launched with the sponsorship support of the Coca-Cola company. Produced in the same studio that Don Cornelius used for the nationally syndicated dance/music television show, "Soul Train", "Step by Step"'s audience grew and the show became a success. The dynamic dance duo of Robin and Reggie led the show. The pair spent the week teaching disco dancing to dancers in the disco clubs. The instructional show aired on Saturday mornings and had a strong following. The viewers of this would stay up all night on Fridays so they could be on the set the next morning, ready to return to the disco on Saturday night knowing with the latest personalized dance steps. The producers of the show, John Reid and Greg Roselli, routinely made appearances at disco functions with Robin and Reggie to scout out new dancing talent and promote upcoming events such as "Disco Night at White Sox Park".


title: Disco

text: In Sacramento, California, Disco King Paul Dale Roberts danced for the Guinness Book of World Records. Roberts danced for 205 hours which is the equivalent of 8 ½ days. Other dance marathons took place after Roberts held the world's record for disco dancing for a short period of time.


title: Disco

text: Some notable professional dance troupes of the 1970s included Pan's People and Hot Gossip. For many dancers, a key source of inspiration for 1970s disco dancing was the film "Saturday Night Fever" (1977). This developed into the music and dance style of such films as "Fame" (1980), "Disco Dancer" (1982), "Flashdance" (1983), and "The Last Days of Disco" (1998). Interest in disco dancing also helped spawn dance competition TV shows such as "Dance Fever" (1979).


title: Disco

text: Disco fashions were very trendy in the late 1970s. Discothèque-goers often wore glamorous, expensive, and extravagant fashions for nights out at their local disco club. Some women would wear sheer, flowing dresses, such as Halston dresses or loose, flared pants. Other women wore tight, revealing, sexy clothes, such as backless halter tops, disco pants, "hot pants", or body-hugging spandex bodywear or "catsuits". Men would wear shiny polyester Qiana shirts with colorful patterns and pointy, extra wide collars, preferably open at the chest. Men often wore Pierre Cardin suits, three piece suits with a vest and double-knit polyester shirt jackets with matching trousers known as the leisure suit. Men's leisure suits were typically form-fitted in some parts of the body, such as the waist and bottom, but the lower part of the pants were flared in a bell bottom style, to permit freedom of movement.


title: Disco

text: During the disco era, men engaged in elaborate grooming rituals and spent time choosing fashion clothing, both activities that would have been considered "feminine" according to the gender stereotypes of the era. Women dancers wore glitter makeup, sequins, or gold lamé clothing that would shimmer under the lights. Bold colors were popular for both genders. Platform shoes and boots for both genders and high heels for women were popular footwear. Necklaces and medallions were a common fashion accessory. Less commonly, some disco dancers wore outlandish costumes, dressed in drag, covered their bodies with gold or silver paint, or wore very skimpy outfits leaving them nearly nude; these uncommon get-ups were more likely to be seen at invitation-only New York City loft parties and disco clubs.


title: Disco

text: In addition to the dance and fashion aspects of the disco club scene, there was also a thriving club drug subculture, particularly for drugs that would enhance the experience of dancing to the loud, bass-heavy music and the flashing colored lights, such as cocaine (nicknamed "blow"), amyl nitrite ("poppers"), and the "... other quintessential 1970s club drug Quaalude, which suspended motor coordination and gave the sensation that one's arms and legs had turned to 'Jell-O.'" Quaaludes were so popular at disco clubs that the drug was nicknamed "disco biscuits".


title: Disco

text: Paul Gootenberg states that "[t]he relationship of cocaine to 1970s disco culture cannot be stressed enough..." During the 1970s, the use of cocaine by well-to-do celebrities led to its "glamorization" and to the widely held view that it was a "soft drug". LSD, marijuana, and "speed" (amphetamines) were also popular in disco clubs, and the use of these drugs "...contributed to the hedonistic quality of the dance floor experience." Since disco dances were typically held in liquor licensed-nightclubs and dance clubs, alcoholic drinks were also consumed by dancers; some users intentionally combined alcohol with the consumption of other drugs, such as Quaaludes, for a stronger effect.


title: Disco

text: According to Peter Braunstein, the "massive quantities of drugs ingested in discothèques produced the next cultural phenomenon of the disco era: rampant promiscuity and public sex. While the dance floor was the central arena of seduction, actual sex usually took place in the nether regions of the disco: bathroom stalls, exit stairwells, and so on. In other cases the disco became a kind of 'main course' in a hedonist's menu for a night out." At The Saint nightclub, a high percentage of the gay male dancers and patrons would have sex in the club; they typically had unprotected sex, because in 1980, HIV-AIDS had not yet been identified. At The Saint, "dancers would elope to an un[monitored] upstairs balcony to engage in sex." The promiscuity and public sex at discos was part of a broader trend towards exploring a freer sexual expression in the 1970s, an era that is also associated with "swingers clubs, hot tubs, [and] key parties."


title: Disco

text: In his paper, "In Defense of Disco" (1979), Richard Dyer claims eroticism as one of the three main characteristics of disco. As opposed to rock music which has a very phallic centered eroticism focusing on the sexual pleasure of men over other persons, Dyer describes disco as featuring a non-phallic full body eroticism. Through a range of percussion instruments, a willingness to play with rhythm, and the endless repeating of phrases without cutting the listener off, disco achieved this full body eroticism by restoring eroticism to the whole body for both sexes. This allowed for the potential expression of sexualities not defined by the cock/penis, and the erotic pleasure of bodies that are not defined by a relationship to a penis. The sexual liberation expressed through the rhythm of disco is further represented in the club spaces that disco grew within.


title: Disco

text: In Peter Shapiro's ": Throbbing Words on Sound", he discusses eroticism through the technology disco utilizes to create its audacious sound. The music, Shapiro states, is adjunct to "the pleasure-is-politics ethos of post-Stonewall culture." He explains how "mechano-eroticism," which links the technology used to create the unique mechanical sound of disco to eroticism, sets the genre in a new dimension of reality living outside of naturalism and heterosexuality.


title: Disco

text: He uses Donna Summer's singles "Love to Love You Baby" (1975) and "I Feel Love" (1977) as examples of the ever present relationship between the synthesized bass lines and backgrounds to the simulated sounds of orgasms. Summer's voice echoes in the tracks, and likens them to the drug-fervent, sexually liberated fans of disco who sought to free themselves through disco's "aesthetic of machine sex." Shapiro sees this as an influence that creates sub-genres like hi-NRG and dub-disco, which allowed for eroticism and technology to be further explored through intense synth bass lines and alternative rhythmic techniques that tap into the entire body rather than the obvious erotic parts of the body.


title: Disco

text: The New York nightclub The Sanctuary under resident DJ Francis Grasso is a prime example of this sexual liberty. In their history of the disc jockey and club culture, Bill Brewster and Frank Broughton describe the Sanctuary as "poured full of newly liberated gay men, then shaken (and stirred) by a weighty concoction of dance music and pharmacoia of pills and potions, the result is a festivaly of carnality." The Sanctuary was the "first totally uninhibited gay discotheque in America" and while sex was not allowed on the dancefloor, the dark corners, the bathrooms and the hallways of the adjacent buildings were all utilized for orgy like sexual engagements.


title: Disco

text: By describing the music, drugs and liberated mentality as a trifecta coming together to create the festival of carnality, Brewster and Broughton are inciting all three as stimuli for the dancing, sex and other embodied movements that contributed to the corporeal vibrations within the Sanctuary. This supports the argument that the disco music took a role in facilitating this sexual liberation that was experienced in the discotheques. Further, this coupled with the recent legalization of abortions, the introduction of antibiotics and the pill all facilitated a culture shift around sex from one of procreation to pleasure and enjoyment fostering a very sex positive framework around discotheques.


title: Disco

text: Further, in addition to gay sex being illegal in New York state, until 1973 the American Psychiatric Association classified homosexuality as an illness. This law and classification coupled together can be understood to have heavily dissuaded the expression of queerness in public, as such the liberatory dynamics of discotheques can be seen as having provided space for self-realization for queer persons. David Mancuso's club/house party, The Loft, was described as having a "pansexual attitude [that] was revolutionary in a country where up until recently it had been illegal for two men to dance together unless there was a woman present; where women were legally obliged to wear at least one recognizable item of female clothing in public; and where men visiting gay bars usually carried bail money with them."


title: Disco

text: Disco was mostly developed from music that was popular on the dance floor in clubs that started playing records instead of having a live band. The first discotheques mostly played swing music. Later on uptempo rhythm and blues became popular in American clubs and northern soul and glam rock records in the UK. In the early 1940s, nightclubs in Paris resorted to playing jazz records during the Nazi occupation.


title: Disco

text: Régine Zylberberg claimed to have started the first discotheque and to have been the first club DJ in 1953 in the "Whisky à Go-Go" in Paris. She installed a dance floor with coloured lights and two turntables so she could play records without having a gap in the music. In October 1959, the owner of the Scotch Club in Aachen, West Germany chose to install a record player for the opening night instead of hiring a live band. The patrons were unimpressed until a young reporter, who happened to be covering the opening of the club, impulsively took control of the record player and introduced the records that he chose to play. Klaus Quirini later claimed to thus have been the world's first nightclub DJ.


title: Disco

text: During the 1960s, discotheque dancing became a European trend that was enthusiastically picked up by the American press. At this time, when the discotheque culture from Europe became popular in the United States, several music genres with danceable rhythms rose to popularity and evolved into different sub-genres: rhythm and blues (originated in the 1940s), soul (late 1950s and 1960s), funk (mid-1960s) and go-go (mid-1960s and 1970s; more than "disco", the word "go-go" originally indicated a music club). Musical genres, that were primarily performed by African-American musicians would influence much of early disco.