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Presentation on theme: "FOSSILS."— Presentation transcript:


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? Animal dies and is buried by sediment
Extreme pressure turns sediment into stone Skeleton dissolves and leaves a hole/mold Dissolved by ground water Minerals crystallize in hole and a cast is formed Mineral rich water enters mold and leaves minerals 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


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


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


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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