The Earth has undegone several magnetic reversals in the past, in which the north and south poles are reversed for a period of time. When geologists and geophysicists discovered that the crust in the ocean recorded these reversals, it was even more positive proof that the lithosphere had to be in motion, otherwise there would be no "stripes" of normal and reversed polarity crust.
These were some of the final pieces of the puzzle that led to the development of modern plate tectonic theory. Since its emergence in the 's, plate tectonic theory has gained wide-spread acceptance as the model of Earth processes.
Plate tectonics Activities. History of plate tectonics Plate tectonic theory had its beginnings in when Alfred Wegener proposed his theory of "continental drift.
The theory needed an explanation for continental drift, a process that would account for the motion of tectonic plates. The continental drift was strongly criticised during the first half of the 20 th century, until the second world war.
During the war, the latest radar technology was used to map the seafloor. Rapidly, evidence pointing to the process of seafloor spreading and effective plate motion was accumulated. After the war, marine geology was developed, which led to the discovery of the subduction process under the continental margins. Subduction was a perfect way to balance the extension observed at the mid-ocean ridges by recycling the oceanic lithosphere in the mantle.
Plate tectonics theory then became widely accepted among scientists because it relied on hard evidence and could explain most of the modern geological structures such as ocean basins, mountain ranges, and rifts.
Skip to main content. Climate Sea Levels Why will sea level rise not be the same everywhere? How can we date corals? Geology and Tectonics Geology How do we know the age of the seafloor? Why is the seafloor so recent and the continental crust so old? Where do we find the oldest continental rocks and the oldest seafloor? What are the different types of rocks? What is a fossil and what are they used for?
What are hydrothermal vents, and why do we find them along mid-ocean ridges? Tectonic plates move at a rate of one to 2 inches 3 to 5 centimeters per year, according to National Geographic. That's about as fast as your fingernails grow! Because Earth is spherical, its tectonic or lithospheric plates are fractured into dozens of curved sections. Imagine it like a cracked egg shell. Each plate ranges from a few hundred to thousands of kilometers in size, according to the U.
However, according to a article in Nature , earthquakes over the last few decades are evidence that the Indo-Australian plate has cracked over the last 10 million years, creating a separate Indian Plate and Australian Plate which will increase the number of major plates to eight. Whether that new divide counts as a boundary or not, the Pacific Plate is still the largest of all tectonic plates. It measures 39,, square miles ,, square kilometers in size, and lies hidden beneath the ocean.
There are also many smaller plates throughout the world. While the Earth is estimated to be 4. That means the oldest seafloor is still only about million years old. The oldest ocean rocks are found in the northwestern Pacific Ocean and the eastern Mediterranean Sea.
Fragments of continental crust are much older, with large chunks at least 3. With clues left behind in rocks and fossils, geoscientists can reconstruct the past history of Earth's continents. Most scientists think modern plate tectonics took over from earlier planetary development about 3 billion years ago , based on ancient magmas and minerals preserved in rocks from that period.
That is because as Africa continues to migrate north it will collide with Europe, a collision that will probably create a Himalaya-scale mountain range. However, Christopher Scotese, one of the scientists who developed these simulations, cautions that it is difficult to predict exactly how the continents will be arranged in millions of years. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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