Plate Tectonic Theory (with Matt Sawatzky)
BEFORE Continental Drift
1) Antonio Snider-Pellegrini created two maps demonstrating how America and Africa continents may have once fit together, then separated.
In 1889, Alfred Russel Wallace had said that the belief that the features of the earth's surface have been subjected to continual mutations had been common among geologists. Also that time had caused changes between land and the oceans.
He said that the first person to bring this up was James D. Dana in 1863 by publishing the 'Manual of Geology'. Dana was very influential in America, and his 'Manual of Mineralogy' is still in print in revised form.
His theory became known as Permanence theory.
Theory of Continental Drift
2) The theory that all the continents formed a single landmass, called Pangaea, before breaking apart and drifting was first explained by Alfred Wegener in 1912. Wegener's theory was more complete than previous ones, but he credited many past authors with the similar ideas.
Wegener was the first to use the phrase 'continental drift' and formally published the hypothesis that the continents somehow drifted apart.
Even though he had lots of evidence of his theory, he couldn't provide a convincing explanation for what might have caused continental drift.
The Theory of Plate Tectonics
3) Although Alfred Wegener was the first to begin to explaini our moving continents, Arthur Holmes, a British geologist, introduced a theory of thermal convection to explain the movement of the Earth's continents in 1929. According to Holmes it was the heating and cooling cycle of the Earth's mantle that caused continental drift. This idea didn't attract much attention at the time.
By the 1960's his idea became more credible because of scientists' increased understanding of the ocean floor by mapping. In 1961 scientists had proposed the process of the sea floor spreading caused by the mantle convection to explain the movement of the Earth's continents and plate tectonics.
The Theory of Hot Spots
4) A Canadian geophysicist J. Tuzo Wilson came up with the 'hot spot' theory in 1963. It explained why although most earthquake and volcanic activity happened at plate boundaries, there are some that occur away from these boundaries.
The theory claimed that small, very 'hot' areas of magma are located under certain points of Earth. These places (hot spots) provide localized heat and that sustain long-lasting volcanic activity on the surface. This volcanism builds up seamounts, and eventually rise above the ocean current, forming volcanic islands.
When islands slowly move away from the hot spot, because of plate tectonics, the magma supply is cut, and the volcano goes dormant. According to Wilson's theory, the Hawaiian volcanoes should be growing older and more eroded the further they are from a hot spot. Once one volcano becomes extinct, another develops over the hotspot, and the cycle is repeated. Wilson's theory is accepted as valid to this day.
By the 1960's his idea became more credible because of scientists' increased understanding of the ocean floor by mapping. In 1961 scientists had proposed the process of the sea floor spreading caused by the mantle convection to explain the movement of the Earth's continents and plate tectonics.
The Theory of Hot Spots
4) A Canadian geophysicist J. Tuzo Wilson came up with the 'hot spot' theory in 1963. It explained why although most earthquake and volcanic activity happened at plate boundaries, there are some that occur away from these boundaries.
The theory claimed that small, very 'hot' areas of magma are located under certain points of Earth. These places (hot spots) provide localized heat and that sustain long-lasting volcanic activity on the surface. This volcanism builds up seamounts, and eventually rise above the ocean current, forming volcanic islands.
When islands slowly move away from the hot spot, because of plate tectonics, the magma supply is cut, and the volcano goes dormant. According to Wilson's theory, the Hawaiian volcanoes should be growing older and more eroded the further they are from a hot spot. Once one volcano becomes extinct, another develops over the hotspot, and the cycle is repeated. Wilson's theory is accepted as valid to this day.
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