GK Question “What Is Earth Made Of?” general knowledge book English 2021 current affairs quiz and answers for class 7, 8, 9, 10, 12 students Exam.

What Is Earth Made Of?

As we know, the earth is a big ball. It is composed of rock to a great extent. The earth on its inside is melted rock, while on the exterior, the cover is of hard rock. Of the total surface of the earth, only one-third is land, while the balance, two-third is water.

The outer crust of the earth to a depth of about 15-50 kilometers thickness is rock. This outer crust is also called “the Lithosphere”. The continents are over high parts, while the low parts hold waters of the oceans, the great inland seas, and lakes. All total water on the surface, including oceans, lakes, rivers, streams are called “the Hydrosphere”.

The examination of the earth is limited to the outermost crust of rock. For this reason, the inside of the earth has not been explored. In digging mines, drilling holes, and wells, it has been known that on the inside of the earth the temperature met is higher and still higher, depending upon the depth reached. The temperature at a depth of about three kilometers is enough to boil water.

The studies of earthquakes have to lead scientists to believe that the rate of increase of temperature on the inside of the earth is not so rapid, as it is in the crust. At the core of the earth, the anticipated temperature may not be beyond 5500 degrees centigrade. We know that rocks melt at about 1220°C, so, the inside of the earth is plenty hot.

The earth’s crust is composed of two layers. The upper layer making continents is of granite and that under layer is of hard ‘basalt’ rock. According to scientists the center of the earth is a huge molten iron ball, the diameter of which is about 6400 Kms. Between the center ball and rocky crust is a shell of about 3200 Kms thickness called “The mantle”. The mantle is probably made of ‘olivine’ rock.