a) The seismograph provides information regarding time, location and magnitude of the earthquake.
b) The seismographs located beyond 145' from epicenter record the arrival of P-waves only.
c) At a seismic station the first waves to arrive are surface waves.
d) The intensity of an earthquake is measured by Mercalli scale.
Seismic waves are the vibrations from earthquakes that travel through the Earth; they are recorded on instruments called seismographs. Seismographs record a zig-zag trace that shows the varying amplitude of ground oscillations beneath the instrument. Sensitive seismographs, which greatly magnify these ground motions, can detect strong earthquakes from sources anywhere in the world. The time, location, and magnitude of an earthquake can be determined from the data recorded by seismograph stations.
At seismic station first waves to arrive are P waves. Then S waves and in the last the surface waves.
Oceanic trenches are morphological feature of divergent plate boundaries.
Plate movement along transform boundaries leads to formation of fold mountains.
Caldera volcanoes are the Extreme Volcanoes. These are the most powerful and catastrophic types of volcanoes in a category by themselves because of the unique way in which they form. This type of volcano is shaped more like an inverse volcano. An enormous magma chamber bulges up beneath the ground from the extremely high pressures of the trapped gases within. Ring-shaped cracks form outward from the magma chamber toward the surface and these act as relief valves for the magma to escape. Once the accumulated pressure has been sufficiently released through a serious of extremely powerful pyroclastic and plinian eruptions, the ground above the magma chamber subsides or caves in, leaving a large depression.
The rocks are stratified rocks rich in fossils of animals and plants.
The rocks are hard and normally crystalline in structure.
Rocks undergo chemical changes or structural modification of minerals because of excessive heat and pressure.
Sedimentary rocks are formed over millions of years when sediments (tiny pieces of rocks and animal skeletons) are pressed together at the bottom of seas and rivers.They are distinguished from other rock types in their characteristic layer formation and are termed stratified rocks. Examples include sandstone, coal and chalk. Some sedimentary rocks contain fossils (bones or shells of living things that were buried long ago and have turned to stone).
Metamorphic rocks are formed when other rocks are changed due to heat or pressure. Examples include slate and marble. Metamorphic rocks are very hard but can be damaged by acids like acid rain (on buildings) or even lemon juice (on worktops!).
c) is marked by a change in velocity of seismic waves at the Moho.
Asthenosphere and outer outer mantle are part of mantle. Lithosphere includes a part of outer mantle.
Seismic wave diffraction shows a boundary between more and less dense rocks that is commonly taken to be the crust-mantle boundary. It's called the Mohorovicic discontinuity or Moho for short. It's usually at 30-40 km depth underneath continents, but can be as deep as 80 km.
(a) The Earth's magnetic poles are inclined approximately 11 degrees from the Earth's rotation axis.
(b) The Earth's magnetic poles are aligned with Earth's rotation axis.
(c) The Earth's magnetic poles are perpendicular to the Earth's rotation axis.
Batholith, is large body of intrusive igneous rock believed to have been crystallized at the considerable depth below the earth's surface.. They are the largest type of pluton. Example of batholith is Idaho batholith which cover surface area of over 15500 kilometer square.
Lopolith these are saucer – shaped features formed beneath the earth's surface through magma intrusion. Lopolith forms great shallow basin when magma solidifies within the crust a good example is bush veld igneous complex of South Africa which is composed of both granite and basic rock.
Laccolith, this is a sheet intrusion that has been injected between two layers of sedimentary rock. The pressure of magma is powerful enough that the overlying strata are forced upward giving laccolith a dome or mushroom like form with generally planar base. Some laccolith can be found in Madagascar and Utah USA where they has been exposed by erosion.
Phacolith, this is lens shaped pluton that occupy either the crest of an anticline or trough of syncline. A good example of phacolith can be seen seen in Corndon hills in Shropshire United Kingdom.
The Dead Sea Transform (DST) fault system, also sometimes referred to as the Dead Sea Rift, is a series of faults that run from the Maras Triple Junction (a junction with the East Anatolian Fault in southeastern Turkey) to the northern end of the Red Sea Rift (just offshore of the southern tip of the Sinai Peninsula). The fault system forms the transform boundary between the African Plate to the west and the Arabian Plate to the east.
The Hawaiian Islands were formed by such a hot spot occurring in the middle of the Pacific Plate. While the hot spot itself is fixed, the plate is moving. So, as the plate moved over the hot spot, the string of islands that make up the Hawaiian Island chain were formed.
Nearly 46.6% of total crust of earth is composed of silicon.
P wave travel fastest through inner core.
The P waves travel fastest through outer mantle. Seismic velocities depend on the material properties such as composition, mineral phase and packing structure, temperature, and pressure of the media through which seismic waves pass.
Seismic waves travel more quickly through denser materials and therefore generally travel more quickly with depth. Anomalously hot areas slow down seismic waves. Seismic waves move more slowly through a liquid than a solid.
Molten areas within the Earth slow down P waves and stop S waves because their shearing motion cannot be transmitted through a liquid. Partially molten areas may slow down the P waves and attenuate or weaken S waves.
In desert and arid regions wind is an important agent of weathering. Abrasion through wind action is important mode of erosion.
Frost action is common in tundra and temperate regions.
The flow of Mississippi river is entirely located in USA.
River Parana flows through Pampas region of South America.