ings ponds, which hold mine waste. The November 12 image shows the orange sediment flowing down a valley through the dark green rain forest. This sediment may contain mining chemicals that could affect the fertility of downstream farmland. Researchers are still testing the water to get a better idea about the contents of the mine waste.
Death Valley 1,000-year Flood Event October 29, 2015
This October, a system of storms caused significant flooding in most of Death Valley National Park, California. Collectively, the area only received 1–2 inches (2.5–5 centimeters) of rain, but the annual average in Death Valley is about 2 inches (5 centimeters). The largest of the storms occurred on October 18. Flash floods from the storm destroyed roads and utilities, and damaged several historical structures. This was the largest flood event in the recorded history of the area.
In this image pair Landsat 8 images contrast October 2014 (a year with typical precipitation) to October 2015. The false color images highlight hydrogeology; the areas in green to blue are the locations with moisture content. Especially striking is the Badwater Basin, normally a dry lake bed. In the 2015 image, it is full of water.
Landsat imagery acquired before and after the flood event will help with monitoring and evaluation of landscape response and impacts.
Landsat 7, which launched on April 15, 1999, has been continuing to acquire land images worldwide for 16 years. Landsat 5 may hold the Guinness World Record for longest Earth-observing satellite at 28+ years, but Landsat 7 also has an impressive track record. In fact, Landsat 7 has now acquired over 2 million images. They are all freely available online at USGS GloVis or EarthExplorer.
Landsat 7 and Landsat 8 acquire over 1,200 new images per day. This is more data than at any other time in the history of the Landsat program.
The 2 millionth Landsat 7 scene includes a portion of northwestern Madagascar, acquired on September 11, 2015. The dark region in the lower left is the Ankarafantsika Nature Reserve. This large area of deciduous forest, savannah, and wetland is protected as a national park. On the left edge of the scene is Mahajamba Bay. This shallow bay contains Madagascar’s largest mangrove ecosystem, with tidal mudflats along the edges of the mangroves.
Vredefort Impact Structure, South Africa October 14 ,2015
The Vredefort Impact Structure is the oldest and largest known impact crater on Earth. The entire crater is believed to have been about 300 kilometers (186 miles) across and was formed when an asteroid struck the Earth over 2 billion years ago. The asteroid that produced the crater is thought to have been about 5–10 kilometers (3–6 miles) in diameter.
The crater’s outline is now mostly hidden because of weathering and erosion. The only remaining visible feature is the crescent-shaped Vredefort Dome, shown in the center of this Landsat 8 image. The remnant dome is thought to have formed as a direct result of the impact. The southeastern portion of the dome has been covered over time by features that were formed later.
The Vaal River cuts across the dome remnant and its different rock layers. The city of Parys sits along the Vaal River near the dome. The multicolored geometric shapes to the left and right of the dome are related to agricultural land use.
The Landsat 8 optical sensor includes numerous spectral bands that can be used in various combinations, allowing users to accentuate and study specific features on the Earth's surface. This false color image uses a combination of visible and invisible (shortwave infrared) wavelengths to highlight the geological features of the area, in contrast to the surrounding agricultural and urban land use.
Nauru is the world’s smallest island country, with only 21 square kilometers (8 square miles) of land area. Since the early 1900s, the tiny island has been mined for its rich phosphate reserves. By 2000, most of the phosphate deposits had been exhausted, and the strip mining and associated activities had denuded up to 80% of Nauru’s surface. The min