A rock is a solid made up of a bunch of different minerals. Rocks are generally not uniform or made up of exact structures that can be described by scientific formulas. Scientists generally classify rocks by how they were made or formed.

Must Read: Minerals: India’s Mineral Resources

Three Major Types of Rocks

Metamorphic Rocks – Metamorphic rocks are formed by great heat and pressure. They are generally found in the Earth’s crust where there is enough heat and to form the rocks. Metamorphic rocks are often made from other types of rock. A sedimentary rock can be changed, or metamorphosed, into a metamorphic rocks such as slate or gneiss. Metamorphic rocks include marble, anthracite, soapstone, and schist.

Igneous Rocks – Igneous rocks are formed by volcanoes. When a volcano erupts, it spews out hot molten rock called magma or lava. Eventually, the magma will cool down and harden, either when it reaches the Earth’s surface or somewhere within the crust. This hardened magma or lava are called igneous rocks. Igneous rocks include basalt and granite.

Sedimentary Rocks – Sedimentary rocks are formed by years and years of sediment compacting together and becoming hard. Generally, something like a stream or river will carry lots of small pieces of rocks and minerals to a larger body of water. These pieces will settle at the bottom and over a really long time (perhaps millions of years), they will form into solid rocks. Sedimentary rocks are shale, limestone, and sandstone.

Also Read: Geothermal Energy

The Rock Cycle 

Rocks are constantly changing in what is called the rock cycle. It takes millions of years for rocks to change.

1. Melted rocks or magma is sent to the earth‘s surface by a volcano. It cools and forms an igneous rocks.
2. Next the weather, or a river, and other events will slowly break up this rocks into small pieces of sediment.
3. As sediment builds up and hardens over years, a sedimentary rock is formed.
4. Slowly this sediment rocks will get covered with other rocks and end up deep in the Earth’s crust.
5. When the pressure and heat get high enough, the sedimentary rock will metamorphose into a metamorphic rock and the cycle will start over again.

Space Rocks 

There are actually some rocks that come from space called meteorites. They may have different elements or mineral make up than a typical earth rock. Typically they are made up mostly of iron.

Have a Look at: Plateau

Interesting Facts about Rocks

  • The word “igneous” comes from the Latin word “ignis” which means “of fire.”
  • Ores are rocks that include minerals that have important elements such as metals like gold and silver.
  • Sedimentary rocks form layers at the bottoms of oceans and lakes.
  • Marble is a metamorphic rocks formed when limestone is exposed to high heat and pressure within the Earth.
  • Layers of sedimentary rocks are called strata.

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    The Vellore Mutiny (July 10, 1806) was
    the first instance of a mutiny by
    Indian sepoys against the British East
    India Company. It predates even the
    Indian Rebellion of 1857 by half a
    century. The revolt, which took place
    in the South Indian town of Vellore,
    was rather brief, lasting only one full
    day but brutal, as mutineers broke
    into the Vellore fort and killed or
    injured 200 British troops, before
    they were subdued by reinforcements
    from nearby Arcot.
    The reasons for the mutiny revolved
    mainly around resentment against
    changes in sepoy dress code in
    November 1805. Hindus were
    prohibited from wearing religious
    marks on their foreheads and
    Muslims were required to shave their
    beard and trim their moustache. This
    created a strong resentment among
    the soldiers. In May 1806, some
    revolting soldiers were sent to Fort St.
    George. Two soldiers — a Hindu and
    a Muslim — were given 900 lashes
    each and their services terminated.
    Nineteen soldiers were punished with
    500 lashes each and forced to seek
    pardon from the East India Company.
    The rebellion was also instigated by
    the sons of the defeated Tippu
    Sultan, imprisoned at the Vellore fort
    since 1799. One of Tipu Sultan’s
    daughters was to be married on July 9
    1806, and the plotters of the uprising
    gathered at the fort under the
    pretext of attending the wedding.
    Two hours after midnight, on July 10,
    the sepoys surrounded the fort and
    killed most of the Europeans. The
    rebels seized control by dawn, and
    raised the flag of the Mysore
    Sultanate over the fort. Tipu’s second
    son Fateh Hyder was declared King.
    However, a British Officer escaped,
    and alerted the garrison in Arcot.
    Nine hours later, the British 19th
    Light Dragoons, led by Sir Rollo
    Gillespie, and the Madras Cavalry
    entered the fort through gates that
    had not been fully secured by the
    sepoys. Nearly 350 of the rebels were
    killed, and another 350 injured before
    the fighting had stopped. Some
    accounts have it that 800 rebel
    sepoys died.

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