Kiel, Germany Different colors in a core reflect changes in the composition of the sediment. The remains of plants and animals, and particles such as dust and clay, accumulate through the years at the bottom of oceans and lakes and gradually build up. Scientists extract cylinders, or cores, of these sediments and analyze the contents for clues about the climate at the time they were deposited.
Scientist examines a sediment core extracted from the ocean floor.
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