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Unformatted text preview: General Oceanography Geology 105 Expedition 7 - Commotion Beneath the Ocean Name__________________ Yes, I understand that skipping answers will receive negative points on course folder (two or more answers skipped will result in a deduction of -5 points; -10 point penalty will be assessed if more than more than 5 answers are skipped, and a penalty of -20 points will be assessed if the expedition is missing from the folder - yes - you can get negative points!) _____________________________ (your signature) SIGN!!! Many of the figures in this handout and the online expedition are derived from "This Dynamic Earth" by Jacqueline Kious and Robert Tilling of the U.S. Geological Survey. (http://pubs.usgs.gov/publications/text/dynamic.html) Remember to use the handout to take notes just as if you were listening to a lecture! Plate tectonics was a revolution in the earth sciences, which was launched by oceanographers. In this class we will use tectonics to examine: the formation and recycling of the seafloor and oceanic lithosphere, formation of trenches, volcanic islands motions of the seafloor marine hazards, such as the locations of earthquakes and volcanoes 1. Introduction Is the Earth a dynamic planet? _______ (yes or no) Why or why not? __________________ ______________________________ From "This Dynamic Earth" by Jacqueline Kious and Robert Tilling of the U.S. Geological Survey. 83 2. The Theory of Plate Tectonics _______________________ _______________________________________ _______________________________________ _______________________________________
What is continental drift? What is the name of the supercontinent? __________________ When did the continents last form a large, single continent? a. 18,000 years ago b. 180,000 years ago c. 1,800,000 years ago d. 18,000,000 years ago e. before 180,000,000 years ago The breakup of Pangea resulted in the formation of the modern ocean basins as continental masses drifted apart, allowing seawater to flow between the land masses. 3. Formation of the Modern Ocean Basins As the continents drift apart, new crust is formed beneath the sea to fill the space. The shorelines of which of the following pairs of continents can be easily seen to match up across an ocean: a) Australia and South America b) North America and Asia c) South America and Africa d) Eurasian and Antarctica 4. Evidence of Continental Fit What types of evidence were used to support the hypothesis of the fit of the continents into Pangea? Some fossils match across oceans when continents are realigned with past positions Some rock types match across oceans when continents are realigned with past positions 84 The distribution of ancient swamps and sedimentary deposits formed by ancient glaciers align in proper places when continents are realigned into their past positions, just like pieces of a jigsaw puzzle. See diagram below From "This Dynamic Earth" by Jacqueline Kious and Robert Tilling of the U.S. Geological Survey. 85 5. Earth's Interior Crust 0-50 km thick 0 (zero kilometers) From "This Dynamic Earth" by Jacqueline Kious and Robert Tilling of the U.S. Geological Survey. List the layers within the Earth _______________ _______________ _________________ _________________ Draw the boundaries between the layers within earth at the true scale on the arrow at the left, starting at the surface of the earth (0 kilometers) at the top and the center of the earth at the bottom (6370 kilometers). Include the thickness of the ocean layer. 6370 kilometers (center of Earth) 86 6. Earth's Magnetic Field The magnetic field is generated by the electrical currents in the liquid outer core. -- You should know the direction and orientation of the lines of force of the Earth's magnetic field Make a sketch of the Earth and surrounding lines of force of the magnetic field (it is nearly a Dipole Field, similar to that of a bar magnet). These lines of force point outward from the southern pole (S) (+ pole), are nearly parallel to Earth's surface at the equator and point in, towards the interior of the Earth, at the northern (N) (-) pole. N Earth S
Question -- The lines of force of the earth's magnetic field: a. point towards the north pole and are nearly parallel to the lines of longitude b. point towards the south pole and are nearly parallel to the lines of longitude c. point towards the North America and are nearly parallel to the lines of latitude d. show no organized behavior or direction 7. Earth as a Heat Engine What is convection? _______________________________________ _______________________________________ _______________________________________
How does convection cause the movement of material within the Earth? _______________________________________ _______________________________________ _______________________________________
87 Which layers in the Earth are involved in convection? ____________________
Draw a picture of convection within the earth _____________________ 8. Mapping the Mid-Ocean Ridge System From National Geophysical Data Center http://www.ngdc.noaa.gov/mgg/image/2minrelief.html Using a red pencil trace in the locations of the mid-ocean ridges on the diagram above 88 Below is a profile of the seafloor across the Atlantic Ocean draw an arrow showing the location of the Mid-Atlantic Ridge? 9. On a Mid-Ocean Ridge - Know how the mid-ocean ridge system encircles the globe and the locations of mid-Atlantic Ridge and East Pacific Rise Figure on preceding page from "This Dynamic Earth" by Jacqueline Kious and Robert Tilling of the U.S. Geological Survey. Know locations of mid-ocean ridges !!!!!!! 89 What are the mid-ocean ridges? a. nonvolcanic mountains b. isolated mountains on the seafloor c. long chains of volcanoes that extend from one ocean basin to the next Rift valley marking divergent plate boundary at mid-ocean ridge 10. Seafloor Spreading Understand this concept! It will be on exam! Make a simple, but very clear diagram illustrating the seafloor spreading hypothesis Include the motions of mantle convection in the diagram above. A portion of the earth's mantle is in slow, constant motion, called convection, because: a. the rocks are radioactive b. temperature of the crust alters the mantle c. temperature affects the density of the rocks, causing warm rocks to be less dense with respect to cold rocks which are relatively more dense d. temperature affects the density of the rocks, causing warm rocks to be more dense and cold rocks to be less dense e. higher density rocks rise whereas lower density rocks sink
Know about the formation of Earth's crust and its movement away from mid-ocean ridges with time. 90 What is meant by the term "marine magnetic anomalies" or sometimes called __________________________ _______________________________________ _______________________________________ _______________________________________
seafloor magnetic stripes? 11. Reading the History in the Magnetic Patterns Draw two pictures, one of the Earth's magnetic field as it is today (so-called normal polarity) and other showing a reversed field (or reversed polarity) 12. Reading the Magnetic Patterns How are the marine magnetic patterns used as scientific evidence of seafloor __________________________________ _______________________________________ _______________________________________ _______________________________________
spreading? 91 13. The Plates List and Know Names of at least 9 of the Major Plates _____________ 3. _____________ 5. _____________ 7. _____________ 9. _____________
1. _____________ 4. _____________ 6. _____________ 8. _____________
2. From "This Dynamic Earth" by Jacqueline Kious and Robert Tilling of the U.S. Geological Survey. 14. More on the Plates __________________________ _______________________________________ _______________________________________
What is the lithosphere? _________________________ _______________________________________ _______________________________________
What is the asthenosphere? 92 Draw a picture showing a plate composed of the rigid lithosphere floating on the hot, mobile asthenosphere. 1 minute essay - Summarize what you learned in this expedition - Avoid the "I learned a lot about" syndrome -- show some insight _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________
Post any questions on this expedition under "Exped 7 Commotion Any Questions?" in WebCT Discussions Remember to e-mail "Bye Don" with End Expedition 7 in Subject Line 93 ...
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This note was uploaded on 05/03/2008 for the course GEOL 105 taught by Professor Reed during the Spring '08 term at San Jose State University .
- Spring '08