The Columbia Glacier descends from an ice field 3,050 meters (10,000 feet) above sea level, down the flanks of the Chugach Mountains, and into a narrow inlet that leads into Prince William Sound in southeastern Alaska. It is one of the most rapidly changing glaciers in the world.
The Columbia is a large tidewater glacier, flowing directly into the sea. When British explorers first surveyed it in 1794, its nose - or terminus - extended south to the northern edge of Heather Island, a small island near the mouth of Columbia Bay. The glacier held that position until 1980, when it began a rapid retreat that continues today.
These false-color images, captured by Landsat satellites, show how the glacier and the surrounding landscape has changed since 1986. The images were collected by similar sensors - the Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) - on three different Landsat satellites (4, 5, and 7).
The Landsat sensors detect light reflecting off the Earth in the short wave-infrared, near-infrared, and green portions of the electromagnetic spectrum. With this combination of wavelengths, snow and ice appears bright cyan, vegetation is green, clouds are white or light orange, and the open ocean is dark blue. Exposed bedrock is brown, while rocky debris on the glacier’s surface is gray.
By 2011, the terminus had retreated more than 20 kilometers (12 miles) to the north, moving past Terentiev Lake and Great Nunatak Peak. In some years, the terminus retreated more than a kilometer, though the pace has been uneven. The movement of the terminus stalled between 2000 and 2006, for example, because the Great Nunatak Peak and Kadin Peak (directly to the west) constricted the glacier’s movement and held the ice in place.
For more info, visit:
http://earthobservatory.nasa.gov/Features/WorldOfChange/columbia_glacier.php?src=features-hp
The Columbia is a large tidewater glacier, flowing directly into the sea. When British explorers first surveyed it in 1794, its nose - or terminus - extended south to the northern edge of Heather Island, a small island near the mouth of Columbia Bay. The glacier held that position until 1980, when it began a rapid retreat that continues today.
These false-color images, captured by Landsat satellites, show how the glacier and the surrounding landscape has changed since 1986. The images were collected by similar sensors - the Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) - on three different Landsat satellites (4, 5, and 7).
The Landsat sensors detect light reflecting off the Earth in the short wave-infrared, near-infrared, and green portions of the electromagnetic spectrum. With this combination of wavelengths, snow and ice appears bright cyan, vegetation is green, clouds are white or light orange, and the open ocean is dark blue. Exposed bedrock is brown, while rocky debris on the glacier’s surface is gray.
By 2011, the terminus had retreated more than 20 kilometers (12 miles) to the north, moving past Terentiev Lake and Great Nunatak Peak. In some years, the terminus retreated more than a kilometer, though the pace has been uneven. The movement of the terminus stalled between 2000 and 2006, for example, because the Great Nunatak Peak and Kadin Peak (directly to the west) constricted the glacier’s movement and held the ice in place.
For more info, visit:
http://earthobservatory.nasa.gov/Features/WorldOfChange/columbia_glacier.php?src=features-hp
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