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Answer:
B.1. The word igneous is derived from the Latin word ignis which means fire. Igneous rocks are formed when magma cools and solidifies. They are also known as Primary Rocks as they were the first rocks to be formed on Earth. Depending on their formation, Igneous rocks have been divided into two types.
Intrusive igneous rocks or plutonic rocks are formed within the earth. When magma cools down and solidifies below the surface of the earth and in the cracks of the crust, it forms intrusive igneous rocks. For example -Granite and Dolerite.
Extrusive igneous rocks or volcanic rocks are formed on the surface of the earth. During a volcanic eruption, magma which is found in the mantle comes out onto the surface of the earth in the form of lava. This lava cools down rapidly to form extrusive igneous rocks. For example - Basalt. The Deccan Plateau in India is made up of basalt rocks.
B.2. Magma is composed of molten rock and is stored in the Earth’s crust. Lava is magma that reaches the surface of our planet through a volcano vent. As they are both molten rock that emerges from below the Earth, it can get confusing identifying one from the other.
B.3. Sedimentary rocks are porous while metamorphic rocks are not porous. Sedimentary rocks may also contain fossils of plants and animals that get buried between the layers where as metamorphic rocks may contain some precious gems like rubies and sapphires. Examples of sedimentary rocks are sandstone, limestone, shale and coal where as examples of metamorphic rocks are limestone changes into marble, shale changes into slate.
C.1. The innermost layer of the earth is known as the core. It is mainly made up of heavy metals such as nickel and iron. For this reason, the core is also known as nife (ni = nickel; fe = ferrous/iron).
C.2. They are mostly formed under water.
They are porous.
They are softer than igneous rocks.
They may also contain fossils of plants and animals that get buried between the layers.
C.3. The word metamorphic means modified or changed. Extreme heat and pressure inside the earth can change the colour, hardness, texture and even the mineral composition of rocks. Igneous and sedimentary rocks change into metamorphic rocks due to such heat and pressure.
C.4. Wind, water, ice, plants and animals break igneous rocks into smaller fragments called sediments. The sediments are transported and deposited elsewhere by the agents of erosion. Over time, these loose sediments are compressed and hardened to form a layer of rocks known as Sedimentary Rocks.
D.1. Our Earth consists of four different layers namely:
Inner core
Outer core
Mantle
Crust
The core is divided into the inner core and the outer core.
Inner Core: The inner core is a thick ball of metal with a radius of 1,200 km. The temperatures reaching upto 6,000 °C.The temperature in the inner core is higher than the temperature of the Sun's surface!
Outer Core: The outer core, on the other hand, is a molten layer of nickel and iron of a thickness of 2,200 km. Temperatures range from 4,000 to 5,000 °C.
Mantle: The middle layer of the earth is known as mantle. The thickness of the mantle is 2,900 km. It is mainly made up of iron, silicon and magnesium. The temperature in the mantle are very high, ranging from 870 to 2,200 °C. Parts of the mantle made up of semi molten rocks known as magma.
Crust: The outermost layer of the earth, comprising tectonic plates which are in constant motion. It is very thin. It is divided into 2 parts is continental and oceanic crusts.
D.2. There are three main types of rocks: igneous rocks, sedimentary and metamorphic rocks. Igneous rocks are formed when magma cools down and solidifies.
Wind, water, ice, plants and animals break igneous rocks into smaller fragments called sediments. The sediments are transported and deposited elsewhere by the agents of erosion. Over time, these loose sediments are compressed and hardened to form a layer of rocks known as Sedimentary Rocks.
Extreme heat and pressure inside the earth can change the colour, hardness, texture and even the mineral composition of rocks. Igneous and sedimentary rocks change into metamorphic rocks due to such heat and pressure.
D.3. The rock cycle carry on how with no starting and no ending. Igneous rocks are eroded, deposited and compressed to form sedimentary rocks. Both rocks are then changed into metamorphic rocks due to extreme heat and pressure, on continuing to be subjected to extreme heat and pressure, can wear away to a molten form, that is magma. This cycle carries on.
This cyclic transformation of rocks is known as the rock cycle.
D.4. Minerals are used in many industries.
Copper is another metal used in everything from coins to pipes. Minerals like copper are used in making electric wires,coins, jewellery etc.
Aluminum obtained from its ore bauxite is used in automobiles and airplanes, bottling industry, buildings and even in kitchen cookware.
Minerals like gold are used to make jewellery,coins etc.
