1. Ch.3, Sec.4 – Looking at Fossils
Fossilized Organisms
- the remains of an organism preserved by geologic processes is called a fossil
- fossils are usually found in sedimentary rock, but can be found in many types of materials
- fossils found in rocks are usually made of bones or shells

2. Ch.3, Sec.4 – Looking at Fossils
- fossils (insects, frogs, lizards) have been found in amber, which is hardened tree sap
- fossils can also be preserved through petrification, in which minerals replace an organism’s tissues

3. Ch.3, Sec.4 – Looking at Fossils
- fossils (woolly mammoths, saber-toothed cats) have been found in asphalt pits (evaporating oil), which can trap animals in them
- the La Brea asphalt pits in Los Angeles have trapped animals for the last 38,000 years!

4. Ch.3, Sec.4 – Looking at Fossils
La Brea Asphalt Pits, Los Angeles, California

5. Ch.3, Sec.4 – Looking at Fossils
- fossils can also be preserved by frozen climates with tundra
- scientists have discovered multiple woolly mammoths in the permafrost tundra of Siberia, in Russia

6. Ch.3, Sec.4 – Looking at Fossils
Other Types of Fossils
- any naturally preserved evidence of animal activity is called a trace fossil
- trace fossils can be tracks, burrows, or animal dung (coprolite)

7. Ch.3, Sec.4 – Looking at Fossils
- fossils can also be preserved in molds & casts
- a cavity in rock where a plant or animal was buried is called a mold
- a cast is an object created when sediment fills a mold and becomes rock

8. Ch.3, Sec.4 – Looking at Fossils
Using Fossils to Interpret the Past
- unfortunately, the fossil record is incomplete because most organisms never became fossils or haven’t been discovered
- using the fossils of plant and land animals allows scientists to reconstruct past climates
- some of the oldest fossils in the world have been discovered at the Burgess Shale Formation in British Columbia, Canada

9. Ch.3, Sec.4 – Looking at Fossils
Using Fossils to Date Rocks
- many fossils are only found in certain layers of rocks, so dating the rocks give us an idea of how old they are
- index fossils are fossils of organisms that lived during a relatively short, well-defined geologic time span
- two perfect examples of index fossils are ammonites & trilobites, which is Ohio’s state fossil
Ammonites
Trilobites

10. Ch.3, Sec.4 – Looking at Fossils