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Our transcription: Evidence of ice ages is not only recorded by the landscape. Scientists have also discovered important clues to Earth's past within glaciers themselves. Glaciers contain within their stratigraphic layers all of the material that fell with the snowfall that incorporated within it. One can liken glaciers as a depositional environment, a glacial environment, and in the deposits contain events of Earth's history that occur simultaneously during the depositional process. You see, ice sheets are essentially atmospheric processes. Practically any material passing through the atmosphere may be trapped in glaciers as they form. Pollen, volcanic ash, and meteorites have been discovered in the ice. Even bubbles of an ancient air have been found representing a valuable record of Earth's past atmosphere and climate.
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