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Texas ISD School Guide
Texas ISD School Guide







Short Stories for Teachers

The Layers Of Earth
By:Alice Kelly

The Earth was formed 4.54 billion years ago by accumulation from a rotating disk of dust and gas. The huge amount of heat energy released out from gravitational energy and from the decay of radioactive elements melted the entire planet, and it is still cooling off today. Denser materials like iron (Fe) sank into the core of the Earth, while lighter silicates (Si), other oxygen (O) compounds, and water rose near the surface.

Basically, the earth's interior is divided into three main layers namely: the crust, the mantle and the inner core. The crust is the earth's hard outer shell or the surface on which we are living. The crust is much thinner than any of the outer layers and is composed of calcium and sodium aluminum-silicate materials. Being relatively cold, the crust is rocky and brittle, so it can fracture in earthquakes.

Mantle is the second layer of the earth and the largest one too. It is made up of minerals like iron, aluminum, calcium, magnesium, silicone and oxygen. The temperature in this layer is estimated to be about 1000 degrees Celsius and the volcano magma is present in this layer itself. For better understanding, we can say that the mantle layer is divided into the upper and lower sections. The upper mantle is much cooler than the lower (deeper) section. The overall thickness of the mantle layer is 2900 kilometers.

The core is the innermost layer of the earth. It is composed of the outer core and the inner core. The outer core is presumed to be liquid because it does not transmit shear (S) waves and because the velocity of compressional (P) waves that pass through it is sharply reduced. The inner core is considered to be solid because of the behavior of P and S waves passing through it.

The structure of the earth is relatively simple to understand. Having knowledge about the earth's interior structure is essential for a better sense of responsibility and knowledge.

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