Q. 7 A
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The structure of the inner and outer part of the earth is totally different. The interior structure of the earth is divided into three major layers: the crust, the mantle and the core. Each layer is rich in different elements and minerals.
• The Crust
It is the outermost layer of the earth. It is fragile in nature. The thickness of the crust varies under the oceanic and continental areas. Oceanic crust is thinner as compared to the continental crust. The thickness of the crust varies from 5km to 30km in which, the mean thickness of oceanic crust is 5 km whereas that of the continental is around 30 km. The continental crust is thicker in the areas of major mountain areas. It is as much as 70 km thick in the Himalayan region. The rocks found in oceanic crust are rich in basalt.
• The mantle
It is the layer which lies above the crust. The mantle extends up to the thickness of 2900km. Mantle is the main source for the volcanic eruption because of the rocks present in the molten form. The major elements found in the mantle are Silica (Si) and Magnesium (Mg), hence it is popularly known as SIMA. In the upper part of the mantle the rock remains solid and inner part of the mantle the rock remains in liquid form. The crust and the uppermost part of the mantle are called lithosphere. Its thickness ranges from 10-200 km.
• The core
The core is the innermost and hottest layer in the earth. It lies just beneath the mantle. It is composed of minerals of Nickel (Ni) and Iron (Fe). Hence it is popularly known as NIFE. There are two types of core, namely solid outer core and Liquid inner core. Since there is a large amount of iron in the core, it is responsible for Earth's Gravitational Force.
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