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What is an index fossil?

Back

An index fossil is a fossil that is used to define and identify a particular time period in the geological time scale. It must be widespread, abundant, and have lived for a short duration.

Tags

NGSS.MS-ESS1-4

Front

What are the characteristics of an index fossil?

Back

1. Must have lived during a short part of Earth's history. 2. Must be found in many different locations. 3. Must be abundant in the rock layers.

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Why are index fossils important in relative dating?

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Index fossils help geologists determine the relative ages of rock layers and the fossils within them, allowing for the correlation of geological events across different regions.

Tags

NGSS.MS-LS4-1

Front

What does it mean if a fossil is found in multiple layers of rock?

Back

It indicates that the organism lived during a time period that spanned those layers, helping to establish the relative age of the layers.

Tags

NGSS.MS-ESS1-4

Front

What is relative dating?

Back

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

Front

What is the principle of superposition?

Back

In undisturbed rock layers, the oldest layers are at the bottom and the youngest layers are at the top.

Tags

NGSS.MS-ESS1-4

Front

What is an intrusion in geology?

Back

An intrusion is a body of igneous rock that has formed from magma that has cooled and solidified beneath the Earth's surface, cutting through existing rock layers.

Front

How do intrusions affect the age of rock layers?

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Intrusions are younger than the rock layers they cut through, meaning the layers must have existed before the intrusion occurred.

Front

What is the significance of abundant fossils in relative dating?

Back

Abundant fossils indicate that the organism was widespread and can be used as index fossils to correlate the ages of rock layers.

Tags

NGSS.MS-LS4-1

Front

What is the difference between a mold and a cast fossil?

Back

A mold fossil is an impression of an organism left in sediment, while a cast fossil is a three-dimensional replica formed when minerals fill the mold.