How are rocks formed?

How are rocks formed?


Image Credit: Flickr User shaire productions, via CC

If someone asked us  “What’s special about rocks?”, we will probably say “Nothing, really!! Just stony, hard things we see around us often”  They are hard and yes they are stony, but there is so much more to rocks than just that. Did you know that rocks are tiny particles tightly cemented together? And that they are often formed over millions of years under extreme pressure and temperature ?

Igneous rock
Image Credit: Flickr User Pretty Poo Eater, via CC

Rocks are formed under extreme conditions. Depending on these conditions rocks are classified into three different kinds.The first kind of rocks are Igneous rocks. ‘Igneous’ in latin means ‘fire’. The way that they are formed is related to fire. When a volcano erupts, lava flows out. Now when this hot lava comes in contact with the outside surface and cold air,  it begins to solidify. The speed of the lava flow to a large extent determines the look and structure of the igneous rock. Basalt and Granite are igneous rocks.

Sedimentary rocks
Image credit: Flickr user Shandchem, via CC

The second kind of rocks are Sedimentary rocks. They are formed when very tiny particles like minerals, plants, bones ( also called sediment) get deposited in one  place over a long period of time. After many years of deposition these particles get compressed into large chunks of rocks that we call sedimentary rocks. Three fourth of world’s land is made up of sedimentary rocks. The coolest thing about sedimentary rocks is that they tell us a lot about the history of our Earth. Sometimes when the layers of sediments gets squeezed together dead animal, plants or a thing gets trapped in between them which leaves an impression. This is what we call a fossil. Chalk, limestone, coal, flint are just some examples of sedimentary rocks.

Metamorphic rocks
Image credit: Flickr user Ricky Cosmos, via CC

The third kind of rocks are Metamorphic rocks. ‘Metamorphic’ means ‘to change form’. These rocks are formed when other rocks change form due to application of high pressure or temperature. For example, if a rock is very deep in the Earth, it has a lot of pressure from above pushing it down. Another example is when layers and layers of sediment press a rock, it is forced to change form. Slate, marble are metamorphic rocks.

So the next time you play Hopscotch, think about where that piece of rock came from?

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