Geocentric Science

Research gathered in the 1950s lead Professor Harry Hess to propose the idea of seafloor spreading.

However, before Harry Hess, Alfred Wegner first purposed the idea of continental drift. The Theory of Plate Tectonics was built upon these ideas.

• Mid-Ocean Ridge: Large-underwater mountain chains are found in all ocean basins. These mountain ranges are the result of a divergent plate boundary, where the Earth’s crust is ripped apart as magma rises and forces the lithosphere apart. The older rock is pushed away from the oceanic ridge. The largest mountain range on Earth is the Mid-Atlantic Ridge.

• Rock Age: The rocks that make-up the ocean floor (oceanic crust) are significantly younger than the rocks that make up the continents (continental crust). In addition, the youngest oceanic rocks are found at the mid-ocean ridge and increase in age as distance from the ridge increases. The age of the oceanic rock on one side of the ridge is equal to the age of the oceanic rock on the other side of the ridge at that same distance away from the ridge.

• Paleomagnetism: The mafic oceanic rock (primarily basalt) contains iron minerals. As the lava cools and solidifies, the iron crystals align themselves with the Earth’s magnetic field. The oceanic rocks show that the Earth’s magnetic field has reversed many times throughout Earth’s history. The reversals can be seen in rocks on either side of the ridge. The rocks on one side of the ridge show the Earth’s magnetic field at the time of their formation. This pattern can be observed on the other side of the ridge at the same distance away from the ridge.

• Trenches: The old oceanic crust is pushed away from the oceanic ridge as magma rises to form new rocks at the ridge. Eventually, the oceanic crust is destroyed in a trench. Trenches form when dense rock is forced downwards into the asthenosphere. The plunging oceanic crust grinds and melts as it is forced deeper and deeper into the Earth. Earthquakes and volcanoes are a result of the suducting oceanic crust. (Read more on subduction in the Plate Boundaries article.)