Earth History Review

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What are index fossils?

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Index fossils are fossils of organisms that were widespread but only existed for a short period of geological time. They are used to date and correlate the age of rock layers.

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What does relative dating mean?

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Relative dating is a method used to determine the age of rocks and fossils in relation to one another, without determining their exact age.

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What is radioactive dating?

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Radioactive dating is a technique used to date materials such as rocks or carbon by comparing the abundance of a radioactive isotope to its decay products.

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What is the principle of superposition?

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The principle of superposition states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest layers are at the top.

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What is an intrusion in geology?

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An intrusion is a body of igneous rock that forms when magma pushes into existing rock layers and solidifies.

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How do scientists use core samples?

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Scientists analyze core samples to study the layers of sediment and rock beneath the Earth's surface, which helps in understanding geological history.

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What is the significance of fossil correlation?

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Fossil correlation is used to match rock layers from different locations based on the fossils they contain, helping to establish relative ages.

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What is the difference between absolute and relative age?

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Absolute age is the actual age of a rock or fossil in years, while relative age is its age compared to other rocks or fossils.

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What is the Law of Original Horizontality?

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The Law of Original Horizontality states that layers of sediment are originally deposited horizontally under the action of gravity.

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What are sedimentary rocks?

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Sedimentary rocks are formed from the accumulation and compaction of mineral and organic particles, often containing fossils.