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Ask me! No?

C O V E R  S T O R Y

GEOLOGY GYAN
Rock solid. Steady as a rock. Rock hard.

Have you noticed it? Whenever we want to describe something permanent, immovable, or resilient we invariably drag rocks into it. And this is not true of the English vocabulary alone. It is, in fact, an inherent part of every language that human beings speak, across the planet.

It is not difficult to figure out why rocks feature so conspicuously in our dialogues. Solid stones were the basic building blocks of all human civilisations. Towns, cites, roadbeds, bridges, houses — flagship of a thriving urbane society — were all carved out of rocks.

Even the primitive humans lived in caves with stonewalls that kept the predators at bay.

Rocks are a natural resource that makes up the Earth’s layers and the crust. They are found everywhere, and are a part of all human activities. They produce energy (coal is a rock too!); yield useful minerals; and serve as raw material for concrete. Others serve for toolmaking, from the stone knives of our pre-human ancestors to the chalks used by artists today.

The canvas of stones is vast and eternal. Let’s explore some parts of it...

EARTH ROCKS!

Rocks are naturally occurring combinations of minerals. They can be hard or soft, as small as a grain or as large as a building. Stones are small-sized rocks or their fragments.

Rocks are classified by mineral and chemical composition, by the texture of the constituent particles and by the processes by which they were formed. These indicators separate them into igneous, sedimentary and metamorphic.

The natural transformation of one rock type into the other is known as rock cycle. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. The cycle never stops.

Say, an igneous rock is broken into pieces by wind and water. The same forces carry these rock pieces to another place where they make a layer. The depositions cement together to make a sedimentary rock. In this way, an igneous rock becomes a sedimentary rock. And if heat and pressure is applied to this rock, it may change into a metamorphic one!

So, what role do rocks play in our lives?

ROCKING LIVES
Rocks are everywhere. Quite literally.

IN SPACE

All of us have heard about comets, asteroids and meteoroids… right? Do you know that these are the three main types of rocks found in space?

Yes, even space is dotted with rocks! Space rocks are sometimes called small bodies. The ones that are larger are called minor planets or planetoids. These are also known as Near Earth Objects (NEOs).

All these rocks reveal a lot about our solar system, including its origin!

The three types of rocks:
Igneous rocks : formed when magma (hot liquid made of minerals) cools, either within the Earth’s crust or at the surface. When it cools within the crust, it is known as plutonic or intrusive rock. When it reaches the surface either as lava or fragmental ejecta, it is called volcanic or extrusive rock.

Sedimentary rocks : formed in three ways – from pieces of other rocks joined together; from precipitation of minerals dissolved in water; or from deposition of organic matter.

Metamorphic rocks : formed when the minerals in any type of rock re-arrange under high pressure or temperature. They change into some other form or mineral type.

However, there are no set rules to separate the rocks types. By altering the proportions or properties of their minerals, they change into one another. So, they are merely different points of the continuous series of a rock cycle.
Comets

Comets are bodies of ice, rock, gas and dust. A small one is about the size of a house!

They probably originated in a cold area beyond Neptune and Pluto called the Oort Cloud, which surrounds the solar system. Another area where comets are found is called the Kuiper Belt, which lies just past Neptune’s orbit.

Comets follow a regular orbit around the Sun. They journey on a trail that may take 200 years to complete! And these are just short-period comets!!!

Asteroids Asteroids are odd-shaped heavenly bodies that are made of rock. Some of them are also made of metals such as nickel and iron. Their size can vary – from merely a couple of metres to several hundred kilometers across. The largest asteroid, Ceres, is 960 kilometres wide! Because of their size, asteroids are sometimes called minor planets or planetoids. Some asteroids even have moons that orbit them.

Most asteroids orbit the Sun in a region between Mars and Jupiter – the Asteroid Belt. Sometimes, they even venture into Earth's orbit.


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