Structure of Earth
Structure of Earth
Structure of Earth: Earth consists of several layers, each layer having different physical properties.
Beneath Earth's crust is layer called the mantle. The upper part of the mantle is a rigid solid like the crust. For this reason, the crust and the upper mantle are together known as the lithosphere (litho means rock). The lithosphere forms Earth's tectonic plates.
Beneath the lithosphere, the rock of the mantle behaves as a 'plastic' solid. This means the rock is flexible and can flow very slowly, similar to plastic that has been heated. This 'plastic' layer of the mantle is known as the asthenosphere. The tectonic plastic 'float' on the asthenosphere and so can move slowly across it.
The middle is very hot, and becomes hotter as its depth increases. Some of this heat probably dates back to the formation of Earth. Some new heat is created by friction due to moving rocks and also to the decay of radioactive elements. The heat is continually passing from deep in the Earth to the surface.
The core of Earth is very dense and is composed mostly of iron and nickel. The inner core is solid, but the outer core is liquid and can flow, scientists believe this gives Earth its magnetic field.
Why do the plates move ? : - There are two main theories for hos the plates move on the asthenosphere. One is that plates are dragged along as the hot magma in the asthenosphere rises up and then flows under the plates, creating convection currents. As the liquid rock flows, the enough to move them. Figure 10.1.9 shows the convection currents that might carry the plates along.
The other theory is that gravity is involved in moving tectonic plates. This could happen in two very different ways :
The core of earth is composed of __________. | |||
| Right Option : A | |||
| View Explanation | |||
With increase in depth of the Earth, temperature _____________. | |||
| Right Option : A | |||
| View Explanation | |||
Which of the following layers form the lithosphere ? | |||
| Right Option : D | |||
| View Explanation | |||
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