ESS15_LEC6F10_PTect2_2perpage

ESS15_LEC6F10_PTect2_2perpage - Introduction to...

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1 Introduction to Oceanography • Lecture 6: Plate Tectonics 2 San Andreas Fault, Carrizo Plain, CA. Wikimedia Commons, Ian Kluft CC A S-A 3.0, http://commons.wikimedia.org/wiki/File:Kluft-photo-Carrizo-Plain-Nov-2007-Img_0327.jpg Introduction to Oceanography •1st lab quizzes this week! Plate Boundary: San Andreas Fault, CA Plate Boundary: Afar-Red Sea-Gulf of Aden, Africa. NASA Visible Earth, Public Domain. http:// visibleearth.nasa.gov/view_rec.php?id=3187
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2 Wegener’s Continental Jigsaw Puzzle Opening of the Atlantic, Antonio Snider-Pellegrini, 1858, Public Domain Gondwanaland affinities, USGS, http://pubs.usgs.gov/gip/dynamic/continents.html, Public Domain Large Earthquakes, 2000-2008 NSF/Caltech, www.nsf.gov%2Fnews%2Fmmg%2Fmedia%2Fimages%2Fglobal_seismicity_h.jpg, Presumed Public Domain
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3 USGS Natl. Earthquake Center, Public Domain S. Korea China Russia Japan Earthquakes near Trenches Trench USGS Natl. Earthquake Center, Public Domain A B Star shows location of magnitude 8.3 Kurile Eq, 11/15/2006 Records of Earth’s magnetic field • Convection in outer core generates the Earth’s magnetic field – Dominantly dipolar magnetic field • like a bar magnet aligned near the rotation axis – Magnetic poles reverse locations ~1/250,000 years – Last reversal ~780,000 years ago E. Schauble, modified from NASA and JrPol Creative Commons images
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4 Dating rocks with magnetism At volcanoes, molten rock erupts and cools. As it cools crystals form (it solidifies). Some crystals with iron in them are magnetic. They tend to line up with the Earth’s magnetic field when they cool down. If the Earth’s magnetic field reverses, the crystal magnets stay put -- they are frozen in place. A magnetometer towed behind a boat will pick up a weak field if the crystal magnets point the opposite direction from the Earth’s field. (They partly cancel each other out). A magnetometer will pick up a strong field if the crystals point the same direction and the Earth’s magnetic field. Earth’s feld
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This note was uploaded on 12/01/2010 for the course GEOG ESS15 taught by Professor Aurnou during the Fall '10 term at UCLA.

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ESS15_LEC6F10_PTect2_2perpage - Introduction to...

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