A team of scientists discovers fossilized coral deep beneath the sandy surface of a desert in North Africa. Coral usually grows in warm, shallow ocean water.

PART A: A group of scientists are studying rock layers in four different locations. They record the types of fossils found in each layer.

PART B: A group of scientists are studying rock layers in four different locations. They record the types of fossils found in each layer.

Geologists are studying an area where a volcano erupted thousands of years ago. The layers of rock around the volcano show signs of the past eruption.

Scientists send a special drill to take samples from deep under the ocean floor.

Look at the drawing of the rock layers and the fossils. A student made this model to show what happens over time.