2.5 Geologic Timeline

Front

What does the law of crosscutting state?

Back

The law of crosscutting states that a fault or intrusion is younger than the rocks it cuts through.

Front

What is the significance of the Precambrian Time in the geologic timeline?

Back

Precambrian Time is the earliest part of Earth's history, covering about 88% of geological time, and it precedes the Paleozoic Era.

Front

How long ago did the Earth form?

Back

The Earth formed approximately 4.6 billion years ago.

Front

What does the law of superposition state?

Back

The law of superposition states that in undisturbed sedimentary rock layers, younger rocks lie above older rocks.

Front

Which fossil is considered the oldest among trilobites, ammonites, crinoids, and gastropods?

Back

Trilobites are considered the oldest among these fossils.

Front

What is relative dating in geology?

Back

Relative dating is a method used to determine the age of rocks and fossils in relation to one another, without assigning a specific numerical age.

Front

What is an unconformity in geological terms?

Back

An unconformity is a surface of contact between two groups of unconformable strata, indicating a gap in the geological record.

Front

What is the difference between absolute dating and relative dating?

Back

Absolute dating provides a specific age or date for a rock or fossil, while relative dating places events in order without exact dates.

Front

What are index fossils and why are they important?

Back

Index fossils are fossils of organisms that were widespread but only existed for a short period of time, used to date and correlate the age of rock layers.

Front

What is the significance of the Cenozoic Era?

Back

The Cenozoic Era is known as the 'Age of Mammals' and is significant for the evolution of mammals and birds after the extinction of the dinosaurs.