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From: Dan Richter (1:317/3)
To: All
Date: Wed, 19.05.21 13:00
MODIS Pic of the Day 19 May 2021
May 19, 2021 - The Mackinac Strait



Thousands of years ago, during the Wisconsin Ice Age, much of North
America found itself buried under a vast sheet of ice which was as much
as two miles (3.2 km) thick in some areas. While the continents were
roughly the same size and shape as they were now, the landscape was
being ground and shaped into valleys and mountains under the weight of
the shifting ice.

Eventually, the melting glaciers stopped grinding forward and began to
retreat, slowly melting and filling basins with water. As the
Laurentide ice sheet retreated northward, a massive lake formed over
lands belonging to modern-day Canada and United States. Over time –
lots of time – the slow lifting of the bedrock as it was freed from the
weight of the ice sheet began to change the shorelines and Lake
Superior, Lake Michigan, and Lake Huron emerged. About 3,000 years ago
these lakes attained their present shape. Because of their positively
glacial start, the North American Great Lakes are unique among the
world’s large lakes in that their basins are linked together and form
one continuous drainage basin. Together, they constitute the greatest
freshwater system on Earth, covering an area larger than Texas and
about half the size of Alaska. Starting in Lake Superior, the water
flows out the lake’s southeastern tip down the St. Marys River into
Lakes Michigan and Huron.

On May 17, the Moderate Resolution Imaging Spectroradiometer (MODIS) on
board NASA’s Aqua satellite acquired a true-color image nearly-centered
on the Straits of Mackinac, a stretch of water five miles wide that
separates Michigan’s lower and upper peninsulas. The strait connects
Lakes Michigan (left) and Huron (right). Lake Superior, which connects
to Lake Huron through the St. Mary’s River can be seen in the northwest
(upper left).

The gray smudges seen along the St. Mary’s River marks the twin cities
of Sault Sainte Marie, Ontario, Canada (north) and Sault Sainte Marie,
Michigan, USA (south). The boundary between Canada and the United
States divides Lake Superior, St. Mary’s River, and Lake Huron.

Image Facts
Satellite: Aqua
Date Acquired: 5/17/2021
Resolutions: 1km (169.7 KB), 500m (477.6 KB), 250m (1.3 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC

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