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Chapter 8. itarianism A principle that geologic processes that occurred in the past can be explained by current geologic processes. Volcanism and Erosion.

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Presentation on theme: "Chapter 8. itarianism A principle that geologic processes that occurred in the past can be explained by current geologic processes. Volcanism and Erosion."— Presentation transcript:

1 Chapter 8

2 itarianism A principle that geologic processes that occurred in the past can be explained by current geologic processes. Volcanism and Erosion Uniform p.185

3 Relative Age The age of an object in relation to the age of other objects p.186

4 The law that a sedimentary rock layer is older than the layers above it and younger than the layers below it if the layers are not distrubed Law of Superposition p.187

5 A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time. Un ities p.189 Click Here to see animation Click Here to see animation conform

6 Absolute Age The numeric age of an object or event, often stated in years before the present. Using a process like radiometric dating or carbon dating p.191

7 Rates of Deposition In general, about 30 cm of sedimentary rock are deposited over a period of 1,000 years. However, a flood can deposit many meters of sediment in just one day. p.192

8 Radiometric Dating A method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) and a stable (daughter) isotope. Half-Life: the time required for half of a sample of a radioactive isotope to break down. p.193

9 Carbon -14 Dating Plants absorb Carbon during Photosynthesis Scientists compare the carbon isotopes 12 C and 14 C (radioactive) This can be used to determine the ages of wood, bones, shells and other organic remains that are less than 7,000 years old. p.1

10 Paleontology The scientific study of fossils.

11 Trace Fossils Fossilized evidence of past movement of an animal such as tracks, footprints, borings and borrows. p.199

12 Index Fossils A fossil that is used to establish the age of rock layers because it is: Distinct – features different from other fossils Abundant – occurs in fairly large numbers Widespread – present in scattered rocks Existed only for a short span of geologic time p.200

13 Eras & Periods Precambrian makes up about 88% of Earths history! Most rocks from that time have been severely deformed and altered by plate tectonics. Fossils are rare because life-forms lacked bones, shells or other hard parts to make fossils. The most popular Precambrian fossils are Stromatolites. p.216

14 Eras & Periods Fossils of the first vertebrates appear (Paleo…) Most fossil fuels (coal and oil deposits) formed during the Carboniferous Period. Carbonization is the term for how plant remains were turned into coal and oil.. The Super-Continent Pangea formed at the end of this era – about 250 million years ago! p.218

15 Eras & Periods Mesozoic: known as the Age of Reptiles Dinosaurs first appeared during the Triassic Period, but they really dominated in the Jurassic Period. Dinosaurs supposedly became extinct when a giant meteorite crashed into Earth (impact hypothesis). p.221

16 Eras & Periods Cenozoic Era is known as the Age of Mammals. Human civilization developed during the Quaternary Period. p.224


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