Age of Earth

Front

What is the absolute age of a rock?

Back

The number of years that have passed since the rock was formed, such as 'this basalt layer is 1000 years old +/- 20 years'.

Front

What is the relative age of a rock?

Back

The age of a rock compared to the ages of other rocks, such as 'this rock is older than the rest in the area'.

Front

What marks the beginning of geologic time?

Back

Precambrian Time.

Front

What is an example of extrusion in geology?

Back

Lava that hardens on the Earth's surface, forming igneous rock.

Front

What does the law of superposition state?

Back

In undisturbed horizontal layers of sedimentary rock, the oldest rocks are found at the bottom, and each higher layer is younger than the layer(s) below it.

Front

What is an unconformity in geology?

Back

A gap in the geological record that represents a period of erosion or non-deposition.

Front

What is an index fossil?

Back

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

Front

What is the significance of the Cenozoic Era?

Back

It is the most recent geological era, known as the 'Age of Mammals'.

Front

What is the Mesozoic Era known for?

Back

It is known as the 'Age of Reptiles', which includes the time of dinosaurs.

Front

What is the Paleozoic Era?

Back

An era that preceded the Mesozoic, known for the development of early life forms, including fish and amphibians.