Unit 4: Geologic Time & Dating

Front

What is the law of superposition?

Back

The law of superposition states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest layers are at the top.

Front

What is half-life?

Back

Half-life is the length of time required for half of the radioactive atoms in a sample to decay.

Front

What percent of carbon-14 remains after one half-life?

Back

50% of carbon-14 remains after one half-life.

Front

How do you determine the relative age of rock layers?

Back

Relative age is determined by comparing the position of rock layers to one another, using principles like the law of superposition.

Front

What is absolute dating?

Back

Absolute dating is a method used to determine the actual age of a rock or fossil in years.

Front

What is the difference between relative age and absolute age?

Back

Relative age indicates which rock is older or younger compared to others, while absolute age provides a specific age in years.

Front

What is an eon in geologic time?

Back

An eon is the largest division of geologic time, lasting hundreds of millions to billions of years.

Front

What is an era in geologic time?

Back

An era is a subdivision of an eon, lasting tens to hundreds of millions of years.

Front

What is a period in geologic time?

Back

A period is a subdivision of an era, lasting millions of years.

Front

What is a fossil?

Back

A fossil is the preserved remains or traces of ancient organisms, often found in sedimentary rock.