SPACE — Billions of years ago, the earth’s surface was a sea of burning molten rock. As the boiling magma gradually cools, it forms a rocky shell. Dense minerals coalesce into the planet’s interior, while less dense minerals rise to the surface.
“That’s how plates form on the Earth’s surface,” said Catherine Rychert, a geophysicist at the Woods Hole Oceanographic Institution, Massachusetts. Live Science.
“The plate is the earth’s crust, then a little mantle underneath. Underneath (again) there is a weaker material.”
Weaker materials are hotter and easier to move. The difference in strength between the various layers allows the overlying plates to move, rub together, deviate from each other, and collide.
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In these zones, rifts and mountains form, including volcanoes, and of course earthquakes. All of that ultimately triggers life.
But, how many plates cover the surface of our earth? The answer ranges from dozens to almost 100 plates, depending on what indicator is used.
“Most geologists agree that there are between 12 and 14 major (primary) plates covering most of the Earth’s surface,” said Saskia Goes, a geophysicist at Imperial College London.
Each plate has an area of at least 7.7 million square miles or 20 million square kilometers. The largest are the North American, African, Eurasian, Indo-Australian, South American, Antarctic and Pacific plates.
Here we look at some of the major and minor tectonic plates on Earth today. Image: iStock/Getty Images Plus
The most monumental is the Pacific Plate, which covers an area of 39.9 million square miles or 103.3 million square km, followed by the North American Plate, which covers 29.3 million square miles or 75.9 million square km. “Apart from the seven very large plates, there are five other plates that are smaller, namely the Philippine Sea, Cocos, Nazca, Arabian and Juan de Fuca,” said Goes.
Some geologists count the Anatolian Plate (part of the Eurasian Plate) and the East African Plate (part of the African Plate) as separate plates. The reason is, both move at speeds that are clearly different from the main plate. That explains why major plate estimates range from 12 to 14 names.
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And things get more complicated when you look at plate boundaries, where plate tectonics causes plates to break apart into smaller plates called microplates. It is less than 1 million square km in area, and some scientists estimate there are about 57 microplates on Earth.
2023-10-13 15:10:00
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