This brief publication from the Illinois State Geological Survey describes how over the past 1.6 million years, known as the Quaternary (kwa-TURN-ah-ree) Period of geologic time, most of the northern hemisphere above the 50th parallel was repeatedly covered by glacial ice. The cooling of the earth’s surface began at least 2 million years ago, and with that cooling, ice sheets eventually formed in subarctic regions and spread outward until they covered the northern parts of North America. With ongoing climatic change during this period, these ice sheets would form and reform many times.
Found in collection(s)
|Title ||Geosciences Gateways and Resources|
|Description ||The Geosciences Gateways and Resources collection is comprised of web portals, web sites, and individual digital resources in many areas of the geosciences, including atmospheric sciences, environmental sciences, geology, geophysics, hydrology, oceanography, physical geography, soil science, and other Earth science subjects. Here may be found educational materials for geoscience educators and learners (early childhood through graduate school), resources intended for the general public, and materials aimed at research communities in the geosciences.|