1.1.1 EARTH’S STRUCTURE

1.1.1    EARTH’S STRUCTURE

The earth is made up of 3 layers. Each layer has unique characteristics.

  1. Crust
  2. Mantle
  3. Core

                    Outer core

                    Inner core

CRUST: the crust is the outermost layer of earth. This layer, on which life exists, is covered with soil, rock, and water. Relative to the thickness of earth’s outer layer, earth’s crust can be compared in thickness to the shell of an egg or the skin of an apple. The crust is thickest under the continents and thinnest under the oceans. The crust has plates which float on mantle.

Thickness: 10 to 100 km

State: solid

Uses of crust

  1. It is used to grow the plants and agriculture purpose
  2. Mining (for metals and ornamental stones)
  3. We get natural gas and fuel

MANTLE: the mantle is earth’s thickest layer. It is a thick layer of molten rock with the density equal to tar. About 80% of the volume of earth is contained in earth’s mantle, which extends from the base of the crust to the liquid outer core. The mantle is generally considered to exist in a solid state, although high temperatures and pressure can cause some of this solid rock to flow like an extremely thick liquid.

Thickness: about 2900 kilometers

State: solid, but has the quality of plasticity, which means the solid rock in this layer can flow like a thick liquid.

OUTER CORE: most of the rock in earth’s outer core is molten, which means that it acts like a hot liquid. The outer core begins about 3000 kilometers below earth’s surface.

Thickness: about 2250kilometers

State: molten liquid

INNER CORE: earth’s inner core is incredibly dense, because it is under so much pressure. The inner core begins at a depth of about 5150 kilometers below earth’s surface.

Thickness: radius is about 1300 kilometers

State: solid

PLATE TECTONIC THEORY

This theory was explained by ALFRED WEGENER in 1912. He told 225 million years back there was a single continent called as PANGAEA. He mentioned that the PANGAEA started becoming into parts or small pieces and moving into different directions these parts are called as PLATES. These plates float on MAGMA. The magma moment makes the plates move to different directions.

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