Chapter 2

Chapter 2 - Intro to Oceanography: Chapter 2 Plate...

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Intro to Oceanography : Chapter 2 Plate Tectonics (plate = plates of the lithosphere, tekton = to build) I. What Evidence Supports Continental Drift? a. Alfred Wegener was the first to advance the idea of mobile continents in 1912 (continental drift). b. Fit of the Continents i. Sir Francis Bacon believed that all the continents fit together ii. Wegener proposed the large landmass called Pangaea (pan = all, gaea = Earth) and a huge ocean called Panthalassa (thalassa = sea) iii. Sir Edward Bullard and two associates used a computer and a depth of 2000 meters below sea level to fit the continents together (best fit) c. Matching Sequences of Rocks and Mountain Chains i. Wegener found matching sequences of rocks, ages, and structural styles from one continent to another d. Glacial Ages and Other Climate Evidence i. Evidence of ancient glaciation 1. there was a worldwide ice age and even tropical areas were covered by thick ice 2. some continents that are now in topical areas were once located much closer to one of the poles ii. Evidence shows that it is unlikely that the entire world was covered by ice e. Distribution of Organisms i. Mesosaurus (meso = middle, saurus = lizard) fossils were found in South America and western Africa f. Objections to the Continental Drift Model i. Wegener published his ideas in The Origins f Continents and Oceans but received a lot of criticism ii. His hypothesis was correct in principle, but contained incorrect details II. What Evidence Supports Plate Tectonics a. Technology analyzing the way rocks retained the earth’s magnetic field caused scientists to reexamine continental drift and advance it into the more encompassing theory of plate tectonics. b. Earth’s Magnetic Field and Paleomagnetism i. Rockets Affected By Earth’s Magnetic Field 1. Igneous (igne = fire, ous = full of) rocks solidify from molten magma (magma = a mass) either underground or after volcanic eruptions producing lava (lava = to wash) 2. Igneous rock contain magnetite – a naturally magnetic iron mineral 3. Particles of magnetite align themselves to Earth’s magnetic field in magma and the molten material cools and solidifies. 4. Grains of magnetite serve as tiny compass needles that record the strength and orientation of Earth’s magnetic field
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5. After sediments are buried and solidified into sedimentary (seimentum = settling) rock, it contains information of the magnetic field and its origin. ii. Paleomagnetism (paleo = ancient) 1. the study of Earth’s ancient magnetic field 2. analyze not only north-south direction, but also angle relative to Earth’s surface 3. magnetic dip is the degree to which a magnetite particle points into Earth (magnetic inclination) – directly related to latitude
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Chapter 2 - Intro to Oceanography: Chapter 2 Plate...

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