In search of earth’s secrets

The temperature and pressure inside the

Earth increases with depth. The

variations in pressure is due to the

weight exerted by the overlying layers.

The temperature at the centre of the

Earth is about 5000 c. remember that

even iron melts at 1538c.

Based on the analysis of the waves generated during earthquake, the Earth has been divided into different layers.

The comparatively thin outer shell of the Earth.

Approximately 40 km thick.

Two parts-continental crust, oceanic crust.

Located beneath crust.

Extends upto 2900 km from the crust.

Two parts-upper mantle, lower mantle.

Central part of the Earth.

From 2900 km to 6371 km.

Two parts-outer core, inner core.

CRUST MANTLE

CORE

The crust and the upper part of the mantle together are known as lithosphere.

The part beneth the lithosphere, where the materials exist in a partially motlen state rock material (lava) that comes out during volcanic eruptions.

Lithosphere and asthenosphere

Rocks

The lithosphere acquires its name from the material with which it is made (litho means rock). If you look arround you can see rocks of different colours and hardness.

.

This diversity is due to its constituents. The constituents of rocks are called minerals. More than two thousand minerals such as silica, mica, hematite, bauxite, etc have been identified on Earth.

Based on the mode of formation, rocks can be classified into three-igneous, sedimentary, and metamorphic

Rocks

Igneous rocks

Sedimentary rocks

Metamorphic rocks

Igneous rocks ; are formed by the. molten rock material rising through the fissures in the crust and solidifying either on the surface of the Earth or within in the crust itself. Eg; granite, blasat

Metamorphic rocks ; when rocks undergo physical and chemical changes due to high temperature and pressure metamorphic rocks are formed. Eg ; marble, slate.

Sedimentary rocks ; Rocks undergo weathering in course of time. The debris so formed will be deposited in the low region as layers. These materials gradually get lithified and transformed into sedimentary rocks. Eg ; sandstone, limestone.

The rocks may not remain in their original form forever. They are subjected to several changes over time. Observe the diagram.

weathering

Soil evolves

Pedology is the branch of science that deals with soil. The scientific associated with this branch are called pedologists.

The soil today is formed by prolonged processes like weathering of rocks and decomposition of organic matter. It is estimated that more than a thousand years is required for the formation of an inch-thick layer of soil.

Following diagram shows the factors which influencing soil formation.

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RAHANA.NKKSTC