IN: How do you think fossils form? Put your DRW on the box Looking at Fossils 12/16/14 6-4 pgs. 146-150 IN: How do you think fossils form?

Fossil – any naturally preserved evidence of life. What are fossils? Fossil – any naturally preserved evidence of life.

Types of Fossils In Rocks Petrification In Amber Mummification Frozen Fossils In Tar Trace Fossils Molds and Casts

1. In Rocks Occasionally, body parts get buried quickly in sediment and are preserved while the sediment turns to rock.

What type of rock has fossils? Sedimentary

Mineral Replacement 2. Petrification – a process in which an organism’s tissues are completely replaced by minerals.

3. In Amber Hardened tree sap is called amber.

4. Mummification When organisms die in dry places, such as deserts, they can sometimes dry out so fast that there isn’t enough time for even their soft parts to decay.

5. Frozen Fossils Animals freeze in glaciers and are preserved until the glacier thaws thousands of years later.

6. In Tar Organisms get trapped and sink in tar pits which preserve the organism.

La Brea Tar Pits, Los Angeles

7. Trace Fossils – any naturally preserved evidence of an animal’s activity. Tracks

Johnson Farm – St. George, Utah

Coprolites – preserved feces.

8. Molds and Casts A mold is a cavity in the ground or rock where a plant or animal was buried. A cast is an object created when sediment fills a mold and becomes a rock.

Using Fossils to Interpret the Past Fossils can reveal changes that have occurred in parts of the Earth. Coral-reef fossils have been found in Iowa. Fossils of marine organisms have been found on tops of mountains in Canada.

Using Fossils to Date Rocks Index fossils – a fossil that is used to date the rock layers in which it is found. Tropites lived between 230 million and 208 million years ago.

OUT: If you find rock layers containing fish fossils in a desert, what can you infer about that area of the desert?