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Sea Floor spreading is the process that helps to make continental drift and plate tectonics possible. Sea Floor spreading is exactly as it sounds. It is the sea floor spreading itself between continents. The process occurs when magma from the mantle heats up weak spots in tectonic plates. Overtime the heat will make cracks in the weak spots creating rifts or trenches. If the rifts open deep enough magma can pour out in the form of lava cooling and hardening and acting as a natural spreader. This helps to widen the rifts and the process repeats itself.
Scientist believes this how continental drift happened. However instead of the oceanic crust breaking apart, they think it occurred with a large supercontinental plate. The stress on its weak points caused by heated magma forced this supercontinent to break apart creating the modern continents. This lead to the current theory of continental drift that is the foundation of plate tectonics.
One thing that you might be wondering is where is the evidence of seafloor spreading? The answer is ocean ridges. These underwater mountain ranges don’t just pop up. They are places where a great deal of sea floor spreading has occurred over time. As a matter of fact, scientist have taken measurements and samples and found some interesting information. For example beyond the obvious rock formation of basaltic rock formed by the cooling lava, they have also found that ocean ridges have alternating bands of rock with reversed magnetic fields. This all points to the fact that new rock was formed by lava reaching the ocean floor from the mantle.
Sea Floor spreading is still active in many parts of the world’s oceans. This can be observed from under sea vents and trenches. As the sea floor pushes the continents apart the rest of the plates have to go somewhere. The commons destination is to sink beneath continental plates. This is what creates many of the world’s deep sea trenches. These spots are the deepest you places you can go before leaving the crust and entering into the Earth’s mantle.
You can also listen to Astronomy Cast. Episode 142 talks about Plate Tectonics.