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Looking Down On Glacier Bay

Sunday, February 12, 2012

High overhead, the satellite made a sweeping pass over Glacier Bay National Park and Preserve, scanning its cameras across the landscape far below. The resulting image compiled from that shot provides an intriguing image of the park with its rivers of ice, deep bays, and thick forests.

The water in the foreground in the southwest (bottom left) corner of the image is the Gulf of Alaska, with Icy Strait running roughly west to east (horizontally) in from Cape Spencer where the strait meets the Pacific. The foreground glacier is the Brady Glacier. The light gray feature at the foot of the glacier is fine silt dropped by the glacier as it melts. The glacier’s meltwater washes the silt into the Strait, coloring the shallow waters light blue as the silt mixes. The long finger of water dominating the entire scene is Glacier Bay itself. The two points of land at the beginning of the
Bay are roughly where the Grand Pacific Glacier ended when George Vancouver’s crew surveyed the area. The Grand Pacific Glacier now terminates well above Tar Inlet, the finger of water stretching furthermost north (up) at the top of Glacier Bay. The first major inlet on the east (right) coming up from the mouth of Glacier Bay is Muir Inlet. The glaciers feeding into the bay terminated here around 1860. The body of water paralleling the Bay on the eastern edge is Lynn Canal, a body of water also draining into Icy Strait beyond the eastern boundary of the park.

How, exactly, was this image created? Let NASA explain:

The image above is a visualization created by merging imagery from the
Landsat 7
satellite’s Enhanced Thematic Mapper Plus (ETM+) instrument with
elevation data
from the USGS National Elevation Dataset (NED). This true-color image
was created by combining the red, green, and blue wavelengths (ETM+
bands 3, 2, and 1). The resulting image was then draped over a
visualization of the NED data with no
vertical exaggeration. The USGS NED is a merged data product created
from from several sources, prodominately 30-meter resolution elevation
data collected by NASA’s Shuttle Radar Topography Mission (SRTM).

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