Episode 15: Sea floor Luyện thi TOEIC

Episode 15: Sea floor Luyện thi TOEIC Mobile Luyện thi TOEIC, B1, B2: 0974 459 158 - 0918 533 316,

Seafloor spreading is a process of plate tectonics. New oceanic crust is created as large slabs of the Earth's crust split apart from each other and magma wells up to fill the gap.

The large slabs of rock that make up the Earth’s crust are called tectonic plates. As they slowly move away from each other beneath the ocean floor, hot magma from the Earth’s mantle bubbles to the surface. 

This magma is then cooled by seawater. The new rock forms a new part of the Earth’s crust. Seafloor spreading occurs along mid-ocean ridges—large mountain ranges rising from the ocean floor.

The newest oceanic crust is located near the center of the ridge, the actual site of seafloor spreading. The Mid-Atlantic Ridge, which separates the North American plate from the Eurasian plate, and the South American plate from the African plate, is the site of new oceanic crust in the middle of the Atlantic Ocean. 

Over time, new oceanic crust pushes older crust farther away. New bodies of water and even continents can be created through seafloor spreading. The Red Sea, for example, was created through seafloor spreading, as the African plate and the Arabian plate tear away from each other. Today, the northern Sinai Peninsula connects the Middle East (Asia) with North Africa. Eventually, geologists predict, seafloor spreading will expand the Red Sea so that it will completely separate the two continents. 

Rift valleys, which exist on continental crust as well as oceanic crust, can be created by seafloor spreading. Two of the largest rift valleys in the world, the Mid-Atlantic Ridge and the East Pacific Rise, are products of seafloor spreading.

Seafloor spreading disproves an early part of the theory of continental drift. Continental drift was one of the first theories that the Earth's crust was dynamic and always in motion. Supporters of continental drift originally theorized that the continents moved (drifted) through unmoving oceans. Seafloor spreading proves that the ocean floor itself is the site of tectonic activity.

Subduction is the opposite of seafloor spreading. Subduction happens where tectonic plates crash into each other instead of spreading apart. In subduction zones, the edge of the heavier plate subducts, or slides, beneath the lighter one. It then melts back into the Earth's mantle.

Seafloor spreading creates new crust. Subduction destroys old crust. The two forces roughly balance each other, so the shape and diameter of the Earth remains constant.


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