Fossils Geological Time

What is a Fossil? A fossil is the remains or physical evidence of an organism preserved by geologic processes.

Types of fossils Trace Fossils Preserved evidence of animal activity Examples: Foot prints, burrows, animal dung What might these fossils tell us about the animals that left them?

Types of Fossils Molds Casts Fossil that forms when sediments fill in the cavity left by a decomposed organism. A cavity in a rock where a plant or animal was buried.

Where do we find fossils? In sedimentary rocks In Amber In Asphalt In Ice/Frozen climates Fossils can be found all over the world, on every continent.

Fossil Formation

How do fossils form? Fossils form when an animal or plant is quickly buried in sediment. An example is a sandstorm or mudslide that covers the remains of the plant or animal.

How do fossils form cont. Sediment accumulates. Over time they become Sedimentary rocks Water infused with minerals seeps into bone and replaces bone with rock-like minerals. New minerals can replace old minerals Minerals can recrystallize (change their formula) The fossil can be petrified and turned to stone!

Other routes to fossils Amber: Trees create soft, sticky sap Insects, frogs and lizards can get caught in the sap The sap hardens-preserving the animal Cold Temperatures: The cold slows down decay

Other routes to fossils Asphalt Asphalt wells up in pools Crude oil seeps through fissures-lighter elements evaporate Plants and animals get caught Ex: La Brea- California

The lucky few The majority of all living things either decompose because they are exposed to the elements or they are consumed by other animals! Check out the decomposition of this bunny: https://www.youtube.com/watch?v=C6sFP_7Vezg

Why aren’t there more fossils Decomposition Weathering and erosion Magma & Melting Igneous rocks

What do fossils tell us? What the dinosaurs eat What can this tell us? What the dinosaurs eat The size of the animals jaw

Index fossils These are fossils that appear only in certain layers of rock. They help scientists date the rock. These fossils are organisms that lived only during a short, well-defined timespan. How can these fossils help scientists?

I Can How can this help you explain why the fossil record is an incomplete record of life on Earth? How can this help you explain how scientists use fossils?