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Published byKathryn Turner Modified over 9 years ago
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Seafloor Spreading
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Technology Lends A Hand In the 1940’s and 1950’s, two significant inventions were used to help support Wegener’s Theory of Continental Drift. SONAR SONAR The Magnetometer The Magnetometer
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SONAR SONAR is an acronym (Sound Navigating and Ranging). It is a device that can measure the depth of water, find submarines, and… map the ocean floor A fish finder is a simple example of sonar.
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What SONAR Showed Us When we used this new-found technology, we learned that the ocean floor was not flat, but rather… had mountain ranges, canyons, volcanoes, plains and deep sea trenches.
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Mid-Ocean Ridge
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The Magnetometer A magnetometer is a scientific instrument used to measure the strength and/or direction of the magnetic field in the vicinity of the instrument. magnetic fieldmagnetic field The Earth has its own magnetic field. When magma cools, the metallic elements (iron and magnesium) align with the Earths magnetic field Scientists used this to measure the magnetic strength and direction in the rocks that made up the ocean floor
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What We Learned From The Magnetometer We learned that the rocks that make up the ocean floor flip-flop their magnetic polarity every million years or so (scientists still do not know why). We also learned that these patterns mirror one another on either side of the mid-ocean ridges. This was a good piece of evidence to support the idea that the ocean floors are spreading… evenly… in opposite directions… from the mid-ocean ridges As they spread, new floor is created at the ridge, pushing older floor out in opposite directions, leaving older floor further and further out. Along these cracks, earthquakes and volcanoes are common.
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Harry Hess - Putting It All Together During WWII, US Navy Captain Harry Hess spent a lot of time using SONAR and mapping the floor of the Pacific Ocean. He learned that the ocean floor had mountains, ridges, trenches, volcanoes, etc… He also learned that the rocks near the ridges were younger, and the rocks near the trenches were older. He published a report to the Office of Naval Research on his findings. The Navy officially published Hess’s research as the “History of Ocean Basins”
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The Mid-Atlantic Ridge
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So What Does It All Mean? Hess’s research showed that new seafloor was being created at the mid- ocean ridges, and destroyed at the deep sea trenches. This was the missing link (the mechanism) needed to establish Wegener’s theory of Continental Drift. THIS IS A BIG DEAL! This is often regarded as one of the most significant discoveries of the 20 th Century
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Gas Escaping at a Mid-Ocean Ridge
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A Black Smoker Vent
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