Unit 9 Geology part 2
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Describe an "erratic" boulder.
Large boulders, lying free on the surface. These rocks were deposited or left behind by melting, retreating glaciers. These rocks were can be transported great distances (hundreds of miles) from their original location.
In general, what are Ice Ages?
Periods, when a large portion of Earth's land surface was covered by ice.
In the last 4.5 billion years of the Earth's history, about how many periods (ice ages) were there wide spread continental glaciation?
there have been only five periods of widespread continental glaciation.
About when did the last period of very widespread glaciation end?
The last widespread glaciation only began about 2 million years ago.
At about what time did Neanderthal man reportedly become extinct?
About 35,000-28,000 years ago.
Periods of shrinking ice sheets and glaciers (not absence of glaciers but the presence of shrinking glaciers). This represents a period of global warming.
Describe how the "scablands" of Montana were created.
A giant "ice dam" broke, releasing the water of the very large Lake Missoula. the excelled water created a temporary giant river that was +1000 feet deep and moved at 65 mph. The entire lake emptied in two days. that river "scoured" hundreds of square miles removing topsoil (creating the Scablands) and formed giant sand ripple marks.
How were the Great Lakes created?
By immense weight of this glacier and by some gouging by the roots of the glaciers. the bottoms of these lakes are "rebounding"
Are there any remains of the last great US glacier; if so, what is its name?
Barnes Icecap that is found in Canada.
When was the present day Mississippi river drainage created?
At the end of the "last" Ice Age.
What caused the pluvial lakes in the Western US?
Melting of Alpine glaciers, especially in Nevada and Utah.
Discuss the origin of the Great Salt Lake (Lake Bonneville).
Began as a giant fresh water pluvial lake (evaporation resulted in its salty water).
What "cycle" is used to explain ice ages by studying Earth's orbit, tilt and precession?
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