The relative age of rocks

Front

What is an intrusion in geology?

Back

An intrusion is magma that pushes through a body of rock below the surface where it cools and hardens.

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What is an index fossil?

Back

An index fossil is a fossil that helps geologists match rock layers and determine their relative ages.

Front

What does absolute age refer to?

Back

Absolute age is the number of years that have passed since a rock was formed.

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What is relative age in geology?

Back

Relative age is a rock's age compared to other rocks.

Front

What is an extrusion in geology?

Back

An extrusion is lava that hardens on the surface and forms igneous rock.

Front

What is the law of superposition?

Back

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

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What is an unconformity?

Back

An unconformity is a gap in the geological record that represents a period of erosion or non-deposition.

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How do geologists use fossils to determine the age of rocks?

Back

Geologists use index fossils to correlate the ages of rock layers, as these fossils are characteristic of specific time periods.

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What is the difference between absolute age and relative age?

Back

Absolute age provides a specific numerical age of a rock, while relative age places rocks in chronological order without exact dates.

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What is the significance of the principle of original horizontality?

Back

The principle of original horizontality states that layers of sediment are originally deposited horizontally under the action of gravity.