ENGAGE
Pleistocene epoch, ice age, interglacial period, last glacial maximum--it's all a bit confusing until we tease out what these different terms mean and how they help us understand the long history of terrestrial ice on Earth.
Put simply, ice ages are longer periods of colder climate during which ice sheets cover much of the Earth. Interglacial periods are shorter periods of time in which glaciers periodically advance or recede in response to shorter-term climate cycles within the present ice age.
The maximum extent of the last glaciation (LGM) occurred about 18,000 years ago. Except for comparatively brief recent periods, glacial recession has been the norm for quite a while--ever since the last interglacial period ended about 12,000 years ago.
During the LGM, a person could have walked from Alaska to New York across an uninterrupted ice sheet, in places thousands of feet thick. Now, except for the return of seasonal snow each winter, the landforms of most of North America are clear of most of the snow and ice that covered so much it for about 100,000 years.
Thousands of years ago, Earth's climate was again beginning to warm for reasons related to large complex climatic cycles that have regulated ice ages over millions of years.
With just a few million people world-wide at the beginning of agricultural settlement about 10,000 years ago, humanity's carbon footprint was the tiniest fraction of our present scale of carbon combustion. But as populations grew and people migrated, humans became part of the post-glacial biological succession, naturally, as ice sheets and glaciers receded and people advanced into the emerging landscapes.
EXPLORE
Teachers' DomainClimate Change is a TD video that tells the story of climate change as documented in ancient ice stored for thousands of years in Greenland's ice sheet.
Taking Earth's Temperature is a TD video that correlates several methods scientists are using globally to measure the rate and extent of climate change.EXPLORE SOME MORE....
Visit NASA's Earth Observatory to see their animation of global seasonal snow coverage between the Feb. 2000 and Sept. 2009 and observe the interesting patterns of seasonal snow distribution on Earth. Visit the Alaska PaleoGlacier Atlas and find paleoglacier maps detailing regions in Alaska. Observe the modern, late Wisconsin and the maximum extent of Alaska's glaciers during the last glacial period. Helpful Hint: Check Alaska Climate Summaries or National Snow and Ice Data Center for excellent data regarding weather and climate data in specific regions.
EXPLAIN
- Why is change sometimes sudden?
- What are some of the ways Earth's temperature is measured daily?
- Why does one hemisphere get so much more snow than the other?
EXTEND
- What methods and resources do you use to help students understand geologic time?
EVALUATE
- What digital resources regarding ice ages are most useful for your purposes?
