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How Earth’s Past is Revealed.

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Presentation on theme: "How Earth’s Past is Revealed."— Presentation transcript:

1 How Earth’s Past is Revealed.
fossils How Earth’s Past is Revealed.

2 Fossils Evidence of prehistoric life
Traces or remains of living things from long ago Give important clues about Earth’s past

3 Types of fossils Most fossils are hardened animal remains such as shells, bones, and teeth Minerals replace the remains Fossils leave impressions in rock Soft parts of organisms can be preserved in ice, amber, or tar

4 Fossil formation Conditions have to be just right
Remains need to be preserved before decomposition Preserved soft parts are more rare than hard parts Most fossils form in Sedimentary Rock As the sediment settles and forms layers, plant and animal remains can be preserved Why would you not find fossils in Igneous Rock?

5 Fossils in Rock Mold – a visible shape of an organisms remains left after it decays (like a shoe print in the sand) Cast –a solid model in the shape of the organisms remains (if the shoe print was filled in with clay and it hardens into the shape of the shoeprint)

6 Fossils in rocks Petrified Wood –minerals take the place of the cells and harden over time making the organism look like it turned to stone Carbon Films –carbon can be found in every living thing, sometimes the carbon is the only thing left behind after the organism decays, can show details of soft parts missed in other types of fossils

7 Fossils in Rocks Trace Fossils –evidence of an organisms presence in a location, not remains Footprints Trails Animal holes Feces (yes, this is poo!)

8 Ice cores A tubular sample that shows the layers of snow and ice that have built up over thousands of years Found in glaciers and the polar ice caps Scientist analyze trapped air Looks like bubbles in the ice Can tell us about the atmosphere thousands of years ago Dust or ash in the ice means volcanic eruptions Ice layer thickness tells us about temperatures

9 Index fossils Fossil Record – all the fossils that have been found since the study of fossils began Index Fossils Fossils that are unique to a specific time period Remains of organisms that lived for a short period of time Used to date rocks and other fossils

10 Quick check 1. What type of rock will you most likely find fossils?
Igneous Metamorphic Sedimentary Intrusive

11 2. Which part of an ancient reptile would you expect to see in a rock fossil? A. eye B. bone C. heart D. muscle

12 3.Which type of fossil would be most likely to show the complete outline of a leaf? A. petrified wood B. cast fossil C. mold fossil D. carbon film

13 4. Which type of fossil is used to help date the rocks and fossils found around it? A. index B. cast C. mold D. trace

14 5. What do scientist study in ice cores to know about ancient atmospheric conditions? A. pollen B. dust C. ash D. air bubbles


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