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The Ice Age: Glaciers are cool
THE ICY TRUTH!
The Pleistocene in North America
Glaciers moved down and then receded over and over—there have been about 20 ice ages in the last 2.5 million years!
A glacier is a large body of snow, silt, rocks, and ice that accumulates over a long time—even 100s of years!
A glacier can be thought of as a “river” of ice, snow and rocks that flows over land.
It is the weight of the glacier that causes it to flow.
Glaciers form when the amount of snow and ice that falls in a season is more than what melts in the summer.
Today, glaciers cover about 10% of land on Earth. During the last Ice Age, they covered about 32%.
North America during the Pleistocene:
You are here!
How do we know that glaciers have been here?
1. Their movement left striations scraped in the bedrock.
2. Large boulders, called erratics were carried on top of the glacier and dropped when it melted.
3. Glaciers carved out U-shaped valleys as they scraped through mountains.
4. Chunks of ice fall off of the retreating glacier. When they melt, they leave kettle ponds.
Great Pond in Welfleet, MA is a kettle pond.
5. Eskers (long, high ridges of layered sand and gravel) are left when streams of meltwater flow beneath the glacier.
6. Drumlins are long hills with one steep side and one gradual slope.
The geology and geography of Littleton were formed by a glacier.
We live in the Nashua River Valley, which was carved out by a mile-high glacier during the Pleistocene Epoch.
We were covered by Glacial Lake Nashua, which extended from Boylston, MA to Nashua, NH.
Littleton was on one edge of this giant lake, and Tophet Chasm on Oak Hill was the site of a 120 foot waterfall.
The soil in Littleton was deposited by the glacier as it retreated.
Why did the mastodons go extinct? The climate changed drastically and quickly.
They were heavily hunted by humans.
Disease?
A combination of factors…?
Why does any organism go extinct?
Something (or many things) in their environment changes AND
They do not have the adaptation(s) necessary to survive.
