Reading the Rocks
Ages and Eras
Planets and their Pasts
100

Fossils are most commonly found in this type of rock

What is sedimentary rock?

100

This is the method scientists use to determine the absolute age of a fossil.

What is radiometric dating?

100

This planet has surface features that suggest it once had flowing water.

What is Mars?

200

Fossils in deeper rock layers are usually (older or younger?) than fossils found in upper layers.

What is older?

200

The Geologic Time Scale divides Earth’s history into these long periods.

What are eras?

200

The layers of rock on planets help scientists learn about their history, just like on Earth. What are these layers called?

What are strata?

300

The Law of Superposition states that in undisturbed rock layers, the oldest rocks are found where?

What is the bottom?

300

Scientists believe the dinosaurs became extinct due to this major event.

What is an asteroid impact?

300

Scientists compare Earth’s geologic history to other planets using this method.

What is comparative Planetology?

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