Home » Science & Technology , Seafloor Spreading » Bands of magnetic material in the sea floor that have opposite poles, or exhibit magnetic reversal, can provide evidence for sea floor spreading.
Seafloor spreading happens at the bottom of an ocean as tectonic plates move apart. The seafloor moves and carries continents with it. At ridges in the middle of oceans, new oceanic crust is created. The motivating force for seafloor spreading ridges is tectonic plate pull rather than magma pressure, although there is typically significant magma activity at spreading ridges.
At the Mid-Atlantic Ridge (and in other areas), material from the upper mantle rises through the faults between oceanic plates to form the new crust as the plates move away from each other, a phenomenon first observed as continental drift. When Alfred Wegener first presented a hypothesis of continental drift in 1912, he suggested that continents ploughed through the ocean crust. This was impossible: the oceanic crust is both denser and more rigid than continental crust. Accordingly, Wegener's theory wasn't taken very seriously, especially in the United States.
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