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USGS CMG InfoBank: Indicators of Past Ice Ages

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Comment: 14:04 - 15:37 (01:33)
Source: Annenberg/CPB Resources - Earth Revealed 23. Glaciers
Keywords: "Brian Edwards", data, "Ice Age", "Earth's orbit", "drill core", "deep-sea sediment", fossil, microfossil, plant, temperature, ocean, "geologic time", Sun, continent, "plate tectonics", "ocean current", climate, polar, landmass, "ice sheet"

Our transcription: Recent data support this orbital explanation for ice ages.
Drill cores from deep-sea sediments contain fossils of microscopic plants that were sensitive to ocean temperatures -- indicators of past ice ages and the warm times in between.
Using these fossils, scientists have been able to chart the temperature changes in the world's oceans going back nearly a half million years.
Scientists have also shown that these changes can be correlated to variations in the distance between Earth and Sun, which occur with regularity.
But these cyclic changes in Earth-sun geometry have been going on for the entire history of Earth, and glacial epics are uncommon events.
Perhaps the positions of the continents themselves play a role in triggering ice ages.
Throughout Earth's history, plate tectonics has shifted continents, changed their shapes, and altered the pattern of ocean currents around them.
All of these are critical factors in regulating Earth's climate.
And if land masses are near the Poles, they can support ice sheets that could not grow otherwise.
So, ice ages could be triggered by a combination of Earth's orbital pattern and the movement of land masses into polar latitudes.

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