4th October 2019

nps
15

Why are sedimentary rocks found on Earth's surface?

Sedimentary rocks form when mud and sand are deposited in layers on the Earth's surface. The weight of overlying layers compresses the mud and sand to form solid rock. Because sedimentary rocks begin to form at the Earth's surface, they tell us about ancient landscapes.

Moreover, why are you less likely to find fossils in metamorphic rocks?

Sorry - no fossils here! Igneous rocks form from molten rock, and rarely have fossils in them. Metamorphic rocks have been put under great pressure, heated, squashed or stretched, and fossils do not usually survive these extreme conditions. Generally it is only sedimentary rocks that contain fossils.

Why is it not common to find fossils in igneous rock?

They are intrusive igneous rocks because they form from magma underground. Unlike sedimentary rocks, igneous rocks do not contain any fossils. This is because any fossils in the original rock will have melted when the magma formed.

What can fossils tell us about extinct animals?

We only know about extinct groups like dinosaurs, ammonites and trilobites through fossils. Some animals and plant are only known to us as fossils. By studying the fossil record we can tell how long life has existed on Earth, and how different plants and animals are related to each other.
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