Earth's Interior

• Earth is a dynamic planet, constantly changing inside and outside.

Interior of the Earth

• Earth consists of several concentric layers, similar to an onion.
• The crust is the uppermost layer of the earth's surface.
• The crust is the thinnest layer, around 35 km on continental masses and only 5 km on ocean floors.
• Continental mass mineral constituents include silica and alumina, called sial (si-silica and al-alumina).
• Oceanic crust consists of silica and magnesium, called sima (si-silica and ma-magnesium).
• The mantle is beneath the crust and extends to a depth of 2900 km.
• The innermost layer is the core, with a radius of about 3500 km.
• The core is mainly made of nickel and iron, called nife (ni – nickel and fe – ferrous i.e. iron).
• The central core has very high temperature and pressure.
• The crust forms only 1% of the earth's volume, the mantle 84%, and the core 15%.
• The earth's radius is 6371 km.
• The deepest mine is in South Africa at approximately 4 km deep.
• Oil engineers have dug a hole about 6 km deep.
• Reaching the earth's center would require digging a 6000 km hole on the ocean floor.

Rocks and Minerals

• Earth's crust consists of various types of rocks.
• A rock is any natural mass of mineral matter making up the earth's crust and can vary in color, size, and texture.
• Three major types of rocks include: igneous, sedimentary, and metamorphic.
• Igneous rocks form when molten magma cools and solidifies and are also called primary rocks.
• Intrusive and extrusive rocks are the two types of igneous rocks.
• Lava is fiery red molten magma from the earth's interior that cools rapidly on the surface to form extrusive igneous rocks with a fine-grained structure like basalt.
• The Deccan plateau is made up of basalt rocks.
• Intrusive igneous rocks form when magma cools slowly inside the earth's crust, resulting in large grains, such as granite.
• Grinding stones are made of granite.
• Sediments are small fragments of rocks broken down by rolling, cracking, and hitting each other and are transported and deposited by wind, water, etc.
• Sedimentary rocks form when loose sediments are compressed and hardened into layers, such as sandstone made from grains of sand; these rocks may contain fossils.
• Fossils are remains of dead plants and animals trapped in rock layers.
• Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure, like clay changing into slate and limestone into marble.
• Rocks are used for making roads, houses, and in games.
• The transformation of one type of rock into another in a cyclic manner is known as the rock cycle.
• Molten magma cools and solidifies to become igneous rock.
• Igneous rocks break down into sediments that form sedimentary rocks.
• Igneous and sedimentary rocks, when subjected to heat and pressure, change into metamorphic rocks.
• Metamorphic rocks under great heat and pressure melt down to form molten magma, which cools and solidifies into igneous rocks again.
• Rocks are made up of different minerals that are naturally occurring substances with certain physical properties and definite chemical composition.
• Minerals are important to humankind and used as fuels (coal, natural gas, petroleum), in industries (iron, aluminum, gold, uranium), in medicine, and in fertilizers.