EVSC101 Chapter 6 review

EVSC101 Chapter 6 review - EVSC chapter 6 I. Theory of...

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EVSC chapter 6 I. Theory of plate tectonics - a. Theory of global tectonics in which the lithosphere is segmented into several plates that move about relative to one another by floating on and gliding over the plastic asthenosphere. Seismic and tectonic activity occurs mainly at plate boundaries. b. Theory was not articulated until the late 20 th century, nearly 200 years after Huton. c. Gives us a context for understanding the various environments of formation of the three rock types. d. Theory not developed until the 1960s i. Foreshadowed by Alfred Wegener who noticed that the African and south American coastlines on opposite side of the Atlantic Ocean seemed to fit together.----wasn’t the first to make observation, but was the first to pursue it. ---- PANGEA (northern part=Laurasia, southern part= Gondwanaland). Existed 300- 200 million years ago. ---died 30 years before theory was accepted (german trained as an astronomer) ii. Continents apparently moved northward and the Atlantic Ocean opened up. iii. Areas bordering the present-day Atlantic Ocean had matching rock types that lined up across continental boundaries. iv. Suggested that each species, rather than migrating across open ocean, had evolved and spread over that part of Pangea before the supercontinent broke apart. v. Fossils found nowhere else in the world suggested proximity of continents in the past 1. Distribution of fossils across the southern continents of Pangea vi. Glacial deposits and ice movement directions across the southern continents that suggest past juxtaposition 1. Leaves striations on underlying bedrock vii. Certain types of sedimentary rocks form in different climate zones---each rock reflects the latitude at which it was formed. e. Theory of continental drift- concepts of a single supercontinent that broke apart to form the modern continents. i. Skeptical scientists wanted an explanation of the mechanism of continental drift.
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1. Wegner suggested two possibilities: the continents plow their way through the oceanic crust, shoving it aside…. Second: that continental crust slides over oceanic crust. II. The Earth’s layers. a. Crust i. Outermost and thinnest layer ii. Consists of hard, strong rock. iii. Crust beneath the ocean differs from that of continents- between 4-7 kilometers thick and is composed of mostly dark, dense basalt. iv. Continental crust- 20-40 kilometers, under mountain ranges it can be 70 km. composed primarily of light-colored, less dense granite. b. Mantle i. Almost 2,900 km thick and makes up 80% of earth’s volume. ii. Composed of peridotite, which is denser than the basalt and granite of the crust and dark in color. iii. Chemical composition is probably similar through the entire mantle, temperature and pressure increase iwht depth. iv. Temp at top of mantle- 1,000 celcuis, and near the mantle/core boundary- 3,300
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EVSC101 Chapter 6 review - EVSC chapter 6 I. Theory of...

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