Earth History

Front

What can scientists conclude if they find an ice core from 30,000 years ago with different chemicals than today?

Back

The atmosphere 30,000 years ago was different than our atmosphere today.

Front

List Earth's geologic eras from most ancient to most recent.

Back

Precambrian, Paleozoic, Mesozoic, Cenozoic.

Front

How do petrified fossils form?

Back

Minerals soak into and completely replace an organism's remains.

Front

What is the best method for determining the exact age of a rock sample?

Back

Radiometric (radioactive) dating.

Front

What do fossilized seashells found far from the Gulf of Mexico indicate?

Back

The Gulf shoreline was farther inland in the past.

Front

What is the law of superposition?

Back

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

Front

Define relative dating in geology.

Back

Determining the age of rocks or fossils based on their position relative to other rocks or fossils.

Front

What is radiometric dating?

Back

A method used to date materials by comparing the abundance of a radioactive isotope to its decay products.

Front

What are index fossils?

Back

Fossils of organisms that were widespread but only existed for a short period, used to date rock layers.

Front

What does the presence of marine fossils on land suggest about Earth's history?

Back

It indicates that the area was once underwater.