Fossils and Relative Dating

Front

What are index fossils?

Back

Fossils that are used to define and identify a particular time period in the geological time scale, typically because they are widespread and existed for a short duration.

Front

Why are index fossils useful for dating rock layers?

Back

They are found in many different rock layers, allowing geologists to correlate the age of rock layers across different locations.

Front

What characteristics make a good index fossil?

Back

A good index fossil is widespread geographically and has a short lifespan.

Front

Which fossil is considered a good index fossil?

Back

A trilobite that lived in all areas east of the Mississippi River, in large populations during the end of the Paleozoic.

Front

What is the least important characteristic for a fossil to be a good index fossil?

Back

Large size.

Front

What is relative dating?

Back

A method used to determine the age of rocks and fossils by comparing them to other rocks and fossils.

Front

What is the principle of superposition?

Back

In an undisturbed sequence of rocks, the oldest layers are at the bottom and the youngest layers are at the top.

Front

What is an original remain?

Back

The actual remains of an organism, such as bones or soft tissues, preserved in their original form.

Front

What is an example of a substance that can preserve original remains?

Back

Ice.

Front

What is the significance of a fossil's geographic distribution?

Back

A widespread geographic distribution indicates that the organism lived in many different environments, making it a good index fossil.