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Sonar
Sound navigation and ranging uses sound waves to find out the distance to an object. This assisted scientists who wanted to find out the depth of the ocean. -
Continental Drift
Alfred Wegener proposed a hypothesis that the continents had once been joined to form one single supercontinent called Pangaea. The supercontinent had slowly drifted apart after many years. Wegener could not explain how the continents moved. -
Thermal Convection
Arthur Holmes stated the idea that Earth's mantle undergoes thermal convection. He thought that the heating and cooling of the mantle would result in a current that would be strong enough to cause the continents to move -
Mid-Ocean Ridges
Ships that were mapping the ocean floor listed the features of the ocean basin. This lead to the discovery of mid-ridges. -
Theory of Plate Tectonics
The plates in Earth's lithosphere move very slowly due to convection currents in the mantle -
Sea-Floor Spreading
Geologist Harry Hess proposed the hypothesis of sea-floor spreading. The hypothesis states that in the process of sea-floor spreading, new ocean floor forms along mid-ocean ridges and moves outward towards ocean basins. It then finally sinks back into the Earth's mantle. -
Glomar Challenger
Core samples were obtainedby the vessel Glomar Challenger. The samples came from the mid-ocean ridge in between South America and Africa. The samples revealed that the rocks that were closer to the mid-ocean ridges are younger than rocks that are farther away.
