Chapter 4 review

What is an intrusion?

• The age of a rock compared to ages of other rocks

• A gap in the geologic record

• An igneous rock layer formed when magma hardens beneath earth's surface.

• Fossils in which minerals replace all of an organism.

Fossils are the preserved remains or traces of

Fossils show scientists what future environments will look like.

• TRUE

• FALSE

What is a petrified fossil?

• Fossils in which minerals replace an organism

• Preserved remains or traces of living things from the past.

• A fossil that was found in the bottom of a body of water

An unconformity is a in the geologic record.

What is the relative age of a rock?

• The number of years that have passed since the rock formed

• Its age compared to the ages of other rocks.

• The numbers of years that have passed since the rock has been discovered

The absolute age of a rock is the number of years that have passed since the rock

• Formed

• Got discovered

• Broke into small pieces

How does that age of an intrusion compare to the ages of rock around it?

• The age of an intrusion differs compared to the rocks around and beneath it

• An intrusion is always older than the rocks around and beneath it

• An intrusion is always the same age as the rocks around and beneath it

• An intrusion is always younger than the rocks around and beneath it

The half-life of a radioactive element is the time it takes for half of the radioactive atoms to decay.

• TRUE

• FALSE

Geologists use radioactive dating to determine the ages of rocks.