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The Continental Drift
Image Alfred Wegener formed the hypothesis that all the continents were once formed together. He named the supercontinent Pangaea. His three major groups of evidence he used were: rock types, ancient climates, and matching fossils. -
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Plate Tectonics
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Sonar Evidence
[Information about sonar](<a href='http://www.visionlearning.com/library/module_viewer.php?mid=65)<a href='http://prezentit.com/static/temp/image/2012/01/05/1201051 Sonar, sound navigation and ranging, is a system that calculates the distance of an object using sound waves. This was useful to get a better visual of how deep the water was by sending waves from the boat. The deeper the water was the longer it took for the waves to return to the boat. Hess used sonar to find mid-ocean ridges. -
Wegener's Hypothesis Dismissed
Image of HolmesInformation People ignored Wegener's hypothesis and thought he was crazy. Arthur Holmes started to experiment with Wegener's idea. He suggested that the thermol convection acted like a conveyor belt, but no one really paid attention to him at the time. -
Earthquake Patterns Provide Evidence For Sea-Floor Spreading
Image of earthquake patterns Kiyoo Wadati and Hugo Benioff discovered a pattern between earthquakes during the subduciton process. They observed that shallow-focas earthquakes occur around and in the deep-ocean trench. The deeper the earthquake, the farther away its focus is. Since the subduction slab gets heated when it gets so deep, no earthquakes were recorded below 700km. The scientists explanation for this pattern is the subduction process. -
Glomar Challenger
Image Glomar Challenger was a drilling ship that was used to collect evidence for sea-floor spreading. It drilled into the crust beneath the sediment of the ocean floor. The data collected provided evidence about how old that part of the ocean floor was.. The oldest part was nearest to the subduction zone and the youngest was near the valley of the mid-ocean ridge. -
The Theory of Sea-floor Spreading
Image of Sea-Floor Spreading Harry Hess formed the hypothesis that new ocean floors form at mid-ocean ridges, then it moves slowly outwards accross the ocean basins, then finally sinks back into the mantle. (like a conveyor belt). -
Plate Tectonics
Image Wegener's hypothesis starting adding up in the 1960s when scientists noticed that the sea-floor spreading could explain part of it. Putting all the pieces together, a Canadian geologist named J. Tuzo Wilson combined all the evidence from sea-floor spreading to other observations together to create a new theory.
