Front

What is the relative age of rocks?

Back

The age of a rock compared to the ages of other rocks.

Front

What does the law of superposition state?

Back

In horizontal layers of sedimentary rock, each layer is older than the rock above it and younger than the rock below it.

Front

What can disturb rock layers?

Back

Erosion, unconformity, and extrusions can disturb rock layers.

Front

Which two continents did Wegener notice fit together like pieces of a puzzle?

Back

South America and Africa.

Front

What is an index fossil?

Back

A fossil that is used to define and identify a particular time period in the geologic time scale.

Front

What is erosion?

Back

The process by which soil and rock are removed from the Earth's surface by natural processes such as wind or water.

Front

What is an extrusion in geology?

Back

The process of magma being pushed out of the Earth's surface, forming volcanic rock.

Front

What is an unconformity?

Back

A gap in the geologic record that occurs when rock layers are eroded or when sediment is not deposited for a period of time.

Front

What is absolute age?

Back

The actual age of a rock or fossil, often determined by radiometric dating.

Front

What is a fossil?

Back

The preserved remains or traces of a once-living organism.