3 test can wegeners hypothesis predict the results

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(3) Test: Can Wegener's hypothesis predict the results for related phenomena? Wegener’s hypothesis was incomplete : If continents drift and oceans close, what happens to the rocks in the ocean crust? However, in 1910’s little was known about the ocean floor and Earth’s interior. Few instruments to make measurements. BUT - from 1930’s through 1950’s much was learned about Earth structure, the age of rocks, and the seafloor. WWII and Cold war ocean surveys , global satellite gravity surveys & global seismometer stations, rocks and sediments provide the necessary clues. Let's explore! USS Sea Owl Today's Lecture: Plate Tectonics The Scientific Method Observations of Plate Tectonics Wegener’s Continental Jigsaw Puzzle Distribution of Earthquakes Magnetic orientation of Rocks Age of sediments Theory of Plate Tectonics today Basics of Plate Tectonics
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1/15/18 4 Earth's seismic Activity Focus: The point in Earth's interior where earthquake energy is released Seismic waves: The energy waves in an earthquake that moves outwards from the focus and make the ground quake Probing the Earth's activity with Seismometers Large Earthquakes, 2000-2008 (C) NSF/Caltech Earthquakes are concentrated in a few “strips” or lines near the Earth’s surface. This suggests “cracks” or boundaries between rigid areas . Observation 3: Earthquake map Observation 4 At trenches (e.g., NE. of Japan) earthquakes get deeper with distance. Earthquakes happen in rocks that are cold & break rather than flow. Deep earthquakes suggest a slab of cold material that was recently at the Earth’s surface. Observation 4: Earthquakes near Trenches A B USGS Natl. Earthquake Center S. Korea Trench A B Star shows location of magnitude 8.3 Kurile Eq, 11/15/2006. USGS Natl. Earthquake Center
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1/15/18 5 Today's Lecture: Plate Tectonics The Scientific Method Observations of Plate Tectonics Wegener’s Continental Jigsaw Puzzle Distribution of Earthquakes Magnetic orientation of Rocks Age of sediments Theory of Plate Tectonics today Basics of Plate Tectonics The 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. Earth’s field Crystals Weak Earth’s field Crystals Strong 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 .
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