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Strata (singular
stratum) are layers of rock laid down over time. They can be
observed in cliff faces or other exposures as bands of different coloured
rocks. Studying different strata is important because they tell
us about the age of fossils and conditions at various times in
the earth's history.
The Grand Canyon
is a fine place to observe these layers. Those at the bottom of
the canyon were laid down first, and successive layers have
built up on top. This means that as you look down the side of
the canyon, you see rocks of an increasing age. |