earth's history with drawings ·...
TRANSCRIPT
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Earth’s History
Over time sedimentary rock has formed and has embedded plant and animal remains
and as a result, scientists have a record of life on earth. Over a long period of time, sediment
accumulates in horizontal layers. The principle of superposition states that the oldest rocks are
found in the bottom layers within the earth. As the layers progress upward, the age of the rock
becomes younger. Within some of the layers of sedimentary rock, fossils can be found of life
forms from the earth’s past.
Fossils are clues about prehistoric plants and animals on earth. If you have ever visited a
museum and witnessed a fossilized skeleton of a dinosaur, you realize how hard it probably was
to remove from the earth and put back together. But, have you ever considered the conditions
it takes for a fossil to form? Usually, when an animal or plant dies, natural conditions lead the
organism to rot away or be eaten by scavengers.
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One way that conditions are set for a fossil to form is by the organism being covered
very quickly by a layer of sediment. Because the body of an animal is covered quickly, it is
preserved, and over time minerals, which are found within the sediment, replace the original
organism’s structure. After minerals replace the original bone, we now find a rock, which is in
an identical shape.
Scientists have used both the sedimentary rock found within the earth’s layers and the
fossils found in such layers to form a geological time scale. Scientists named paleontologists
have been able to find and record different types of fossils, which are exclusive to specific
layers of sedimentary rock. As a result of the paleontologist’s efforts, a scale spanning 4.5
billion years of different life forms has been created.
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1. The principle of superposition states
o A Older rocks are found in shallow layers o B Younger rocks are found in deeper layers o C Older rocks are found in deeper layers o D Younger rocks contain more fossils
2. Fossils are usually found in what type of rock?
o A igneous o B magma o C sedimentary o D metamorphic
3. After studying the layers of rock, types of rock found in each layer and radioactive carbon dating techniques, scientist have been able to develop a
o A geological time scale o B dinosaur map o C rock cycle o D Big Bang Theory
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On a vacation trip to Calvert Cliffs, Tristan and his father found several megaladon shark teeth fossils. The Park supervisor explained that the fossils come from the adjacent cliffs along the beach. Describe how the fossils were preserved and how they were dislodged from the adjacent cliffs. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________