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The brown areas on both ice caps consist of accumulated volcanic ash and other deposits from past volcanic eruptions. The dark cover of volcanic ash from the 2010 eruption is especially prominent on the 2014 image of Eyjafjallajökull.
At first glance, there appears to be remarkable shrinkage of the ice caps by 2014, the situation for most of Iceland’s ice cover. However, the bright white areas in the 1986 image represent fresh snow cover, which is not present in the 2014 image. To monitor the actual changes in the extent of an ice cap, scientists measure changes in the position of the terminus of outlet glaciers.
Landsat is one of several important remote sensing tools being used by glaciologists to map and monitor changes in the Earth’s ice cover over time.
Chesapeake Bay: A Landsat 8 Surface Reflectance Mosaic February 12, 2015
Chesapeake Bay is the Nation’s largest estuary and its restoration and protection is a priority. The USGS provides scientific information to help manage this vital ecosystem. As part of that role, staff at the USGS Earth Resources Observation and Science (EROS) Center created this true color composite image. The image was created using Provisional Surface Reflectance data from five Landsat 8 scenes, acquired in October and November 2014.
Provisional Surface Reflectance processing includes atmospheric correction to reduce haze, aerosol, water vapor, and ozone effects from Landsat Level 1 processed data. The enhanced processing makes this seamless mosaic possible and provides a sharper view of the Earth’s surface, as if there were no atmosphere interrupting the view between the satellite and ground.
Chesapeake Bay is the dark shape stretching up through the center of the image. Sediment in the water appears either light blue or green. Baltimore, Maryland, and Washington, DC, are the two bright areas near the upper left. The peninsula across the Chesapeake from these cities is a patchwork of farm, forest, and protected areas.
Moving water holds potential for generating electricity, and hydroelectric power currently generates over 16 percent of the world’s electricity.
These Landsat images show the site of the Three Gorges Dam in China, which is the largest hydroelectric dam in the world. The dam is over 2,300 meters (1.4 miles) long and forms the straight line across the river in the second image. The project became fully operational in 2012 and has a power generation capacity of 22,500 megawatts. The reservoir created behind the dam stretches 600 kilometers (373 miles) along the Yangtze River and provides water storage for downstream flood control along with electric power.
The Landsat image from 1993 (left) shows the area one year before construction began. The 2013 image (right) was acquired one year after the power plant became fully operational. The second image shows the reservoir created by the dam and the higher water level that now extends into many side valleys. Also visible in the 2013 image is a lock system that supports shipping traffic, as the increased depth and width of the river now permit larger ships to travel this area.
As hydroelectric power continues to expand around the world, Landsat imagery can help monitor the land surface changes and impacts caused by these projects.
The Topaz Solar Farm is one of the largest solar farms in the United States. Located in central California, the 550-megawatt power station consists of 9 million solar panels across 9.5 square miles (24.6 square kilometers). Construction began in 2012 and was completed in late 2014, and the site can now produce enough electricity to power 160,000 homes.
These images, acquired by Landsat 7 and Landsat 8, show the area of the solar farm development. The 2011 image was acquired before construction started and shows that the previous land use was agriculture. The 2015 image shows the completed project. In the second image, the agricultural land use (green blocks) has been replaced by the solar installation (dark blocks). This second image also shows less overall greenness, due to seasonal change.
Landsat ima