Different Varieties Of Rocks

By Author: Ann Philip
Total Articles: 91
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Today I am interested in discussing about rocks. Whenever we go for summer camps or vacation trips, we will make our tents on the base of Rocky Mountains. In our garden, we will use rocks to build attractive structures. We walk on it; hit it with our garden equipments, still it will be there.

The rocks that we see around us are in the form of mountains, canyons, and riverbeds. A chocolate chip cookie is made up of flour, butter, sugar and chocolate, similar to that a rock is made up of two or more minerals. What exactly a rock is? Geologists classified rocks based on their structure, chemical composition and mineral composition. There are some 3000 minerals are found in the world. And a rock can be a combination of any of these minerals.

There are three basic types of rocks – Igneous rock, sedimentary rock and metamorphic rock.

Igneous rock is the most commonly found rock in the earth’s crust. Most of these rocks are formed from a molten material. Towards the inner part of the earth’s crust, the temperature will be very high, so the minerals are in the liquid form called magma. When the temperature ...
... exceeds tolerable levels, magma will be pushed towards the earth’s surface. This magma will cool and become igneous rocks. We can find two types of igneous rocks on the surface of the earth. They are intrusive igneous rocks and extrusive igneous rocks.

When the lava that comes out of the volcano cools slowly and forms rocks with large crystals, they are called intrusive igneous rocks. Extrusive rocks are formed when magma cools quickly and forms smaller crystals. Igneous rocks normally will be light or dark in color and will have no layering. Some common igneous rocks are granite, basalt, gabbro and scoria. We can see granite rocks in all major parts of the continents. Some granite rocks found in Australia is expected to be nearly four billion years old. Basalt is found in regions lava flowing regions like Hawaii, Iceland and major parts of the northwest part of the U.S.

As the name indicates, sedimentary rocks are formed from eroded fragments of other rocks or from the remains of plants or animals. Sedimentary rocks cover almost 75% of the earth’s surface. Sediment is the sand we find at beaches, mud in the bottom of lakes, the pebbles in rivers and even the dust filled shelves. When we got to beach to play beach volleyball remember the sand on which we are playing will become a sedimentary rock within some thousands of years. Scientists get valuable information on earth’s formation from sedimentary rocks. Fossils are frequently found in the sedimentary rock, which comes in layers called strata. Among other sedimentary rocks, organic sedimentary rock is formed from the remains of living things like clamshells, plankton skeleton and dinosaur skeleton. Lager amount of plants deposited on rocks can also form sedimentary rock. These sedimentary rocks in turn give us coal, oil, natural gas and petroleum.

Another type of rock is metamorphic in origin. The metamorphic rocks are sedimentary or igneous rocks that have been morphed into another type of rock due to constant pressure and heat. Metamorphic rocks are formed when magma imposes into existing rock. The heat of the magma bakes the surrounding rocks causing them to change. Two types of metamorphic rocks are contact metamorphic rocks and regional metamorphic rocks. Marble is metamorphosed limestone and quartzite is metamorphosed sandstone. Mississippi marble is a famous metamorphic rock. It is often used for construction purposes and for making sculptures. I collected information about rock and its formation from my personnel PC connected to FiOS Internet. If you interested in knowing more about rock and its combination, then browse on the internet.

Author Bio:- Ann is a freelancer. She likes to write about earth and its formation. She gathers information on earth and creatures living there by browsing her home internet connected to FiOS Internet.