Fossils and Rock Formations

2. Layers of rock that have the same _______ fossils are about the same age, no matter where they are formed.
4. Debris from meteorites and ___________ crashing into Earth can form key beds.
8. Scientists look at the ___________ of fossils to help determine the age of rock layers.
10. Fossils of shells and fins can tell scientists that that rock layer came from a watery _____________.
11. After an earthquake shifts the rock layer and creating a fault, the fault is always __________ than the rock surrounding it.
12. When many species go extinct at the same time, it is called a ______ extinction.
15. The K-T boundary clay layer formed from a meteorite impact at the end of the ___________ era.
16. Scientists can use index fossils to decide the _________ age of other fossils in many different places on Earth.

1. Sea levels of an area going up and down over time is how fossils of land animals can appear __________ layers of marine fossils.
3. A process called folding tilts and bends the rock layers. This can form a __________.
5. A key bed is a layer of rock that scientists can clearly ____________.
6. Trilobites, a form of ancient marine ____________, are well-known index fossils.
7. Layers of ____________ rock change and can form mountains.
9. An ______________can cause an area's rock strata to shift downward.
13. Scientists study how rock ___________ change. The changes tell a lot about the history of Earth.
14. ________ are caused by deep cracks in the Earth's crust.