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FOSSILS. What is a fossil? Remains of once living animals or plants Represent ancestors of organisms living today.

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Presentation on theme: "FOSSILS. What is a fossil? Remains of once living animals or plants Represent ancestors of organisms living today."— Presentation transcript:

1 FOSSILS

2 What is a fossil? Remains of once living animals or plants Represent ancestors of organisms living today

3 Does every organism turn into a fossil? No - Normally they rot or get eaten If the conditions are correct they can be buried quickly and fossilized – 5 Different steps

4 How are fossils formed? 1.Animal dies and is buried by sediment 2.Extreme pressure turns sediment into stone 3.Skeleton dissolves and leaves a hole/mold – Dissolved by ground water 4. Minerals crystallize in hole and a cast is formed – Mineral rich water enters mold and leaves minerals 5. Millions of years later, the fossil is exposed on the Earths surface – Earthquakes, mountain building, construction, digging/drilling

5 What do fossils tell us? How plants and animals used to live – Individual? Group? Where plants and animals used to live How plants and animals from the past are related to the ones today How plants and animals develop What type of animals/plants used to be present

6 What different types of fossils are there? Body fossils – Tell us what the animal/plant looked like – Ex: Petrified wood, frozen mammoths, amber Trace fossils – Tell us what the animal did – Ex. Footprints, trackways, Coprolites (poo)

7 How do we get information about fossils? Relative dating – Rock Layers Absolute dating – Radioactive Half-Life

8 How are rock layers formed? Rocks are… – Melted – Cooled – Weathered/ Eroded – Compacted/ Cemented – Heated/ Pressurized

9 How are rock layers formed? Rock layers = Sedimentary Rocks – Formed when particles are deposited on top of other particles – Pressure pushes down – Dissolved minerals form natural glue – Creates rocks at or near the surface

10 Why are rock layers important? Tell our history Geologic Column – Ideal sequence of rock layers that contain known fossils and rock formations. – Arranged from oldest to youngest Gaps in history – Erosion – Natural events – Folding, Faults, Volcanoes

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12 What do the rock layers tell us? When events happened – In general rocks in the same layer happened at the same time Fossils in the same layer lived at the same time

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14 What is radioactive decay? Certain naturally occurring elements are radioactive and they break down at predictable rates Scientists measure the half-life of elements – Half life = the time it takes for half the radioactive element to break down Scientists compare the amount of an element to the initial amount and the half-life to determine age

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16 Why is radioactive decay helpful? Also called carbon dating Allows us to calculate an age Cannot be used for objects older than 70,000 years


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