The structure of the earth
The earth has three major parts-the land part or lithosphere, the water part or hydrosphere and the air part or atmostpere. The lithosphere is the surface on which you live . It is also the earth solid sphere consisting mainly of massive rocks. The massive rocks form large land masses called continent and small island groups . Different land form such as mountains,hills,valleys,plateaus and plains make up the lithosphere.
The hydrosphere include all water forms such as oceans,seas,rivers,lakes,and groundwater found beneath the earth.
Geologists or scientists who specialize on the history and composition of earth study carefully these two major parts of the earth. They study the different layers of the earth and what each layer is made of.
You see only the surface of the earth – the oceans, seas, rivers, rocks, and soil. They cover the earth just like the thick peeling of the pomelo or orange fruit. When you cut open the pomelo, you see layers of pulp inside it. If the earth were cut open, you will see that it is made of three layers. They are the crust, matle and the core.
The topmost layer of the earth is the crust which is made of solid rock. It is thicker under the continents; approximately between 11 to 35 kilometres. But under the oceans, it can be 5 to 12 kilometres thick only. At the lower boundary of the crust is the mohorovicic discontinuity or moho; naned after its discover Yugoslav geologist Andrija Mohorovicic. The moho separates the crust from the next layer beneath it – the mantle.
The mantle is about 2,900 kilometres in depth or thickness. Just like the crust, it is also made of solid rocks. But because of extreme heat and pressure, some of these rocks may even flow very, very slowly.
The core is the innermost part of the earth which is about 3,400...
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