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Transcript of Fossils
These layers are usually ordered with the lowest on the bottom
Law of Superposition & Horizontality
Fossils provide a picture of Earth's past organisms
Fossils also tell us the age of rock layers
What do fossils tell us?
Fossils are usually found in sedimentary rocks.
Where are fossils usually
Most fossils form when living things die and are buried by sediments
The sediments slowly harden (cementation) into rock and preserve the shapes of the organisms
How fossils are formed...
Fossils are the preserved remains or impressions of living things
What is a fossil?
Molds: Hallow area in sediment in the shape of an organism or part of an organism
Example: Shell buried in sediment, sediment hardens and leaves an imprint
Minerals fall into the mold to form a cast, a solid copy of the shape of the original organism
Minerals replace all or part of the organism, "turning it into stone".
Example: Petrified wood - these fossils are formed after sediment covered the wood, and mineral rich water seeped into space's in the plat cells, preserving the wood
years old! >
All living things contain carbon. When sediment buries an organism, the organism evaporates and escapes. A thin film of carbon remains.
Example: thin film of carbon remains that preserves plant leaves and insects
Provide evidence of the activities of ancient organisms
Remains of organisms with little or no change.
Example: animals trapped in tar (La Brea tar pits), insects trapped in amber, woolly mammoths trapped in ice.
How do fossils help scientists?
Scientists who study fossils are called paleontologists.
Fossils provide evidence of how life has changed over time