I am sure you have seen one of these before, they are called rocks. Rocks are naturally occurring mass of minerals. Rocks may be big or small and may be formed in a number of ways.
There are three main types of rocks based on how they are formed:
1. Igneous Rocks: These are formed by the cooling of molten magma.
Magma erupts from active volcanoes. When molten magma cools above the earth surface they are called extrusive igneous rocks and when it cools beneath the earth surface, they are referred to as intrusive igneous rocks.
Remember that, igneous rocks get their name from the Latin word ignis which means fire. They are usually shiny and crystalline in nature. An example of an igneous rock is granite.
2. Sedimentary Rocks: Sedimentary rocks are formed when sediments are deposited over each other in layers for a long period. These deposits solidify as a result of heat and pressure and form sedimentary rocks.
Sedimentary rocks occur in layers. An example of sedimentary rock is limestone.
3. Metamorphic Rocks: These are also known as changed rocks. They do not have any original origin. They are formed when igneous or sedimentary change as a result of high heat and high pressure. An example of metamorphic rock is marble which is gotten from limestone.
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Rocks aren’t just the big hard stuff you see everywhere. They also have great importance too! Rocks break down to form soil. They are also rich in nutrients and form the bulk part of the soil.
Buildings and roads are constructed with rocks. Some rocks are used to decorate and beautify our homes. A lot of people also like to see really big rocks for fun. There are big rocks in Nigeria that are known to attract many tourists and visitors. An example is the Olumo rock in Abeokuta and Zuma rock in Niger state.
Remember, rocks are naturally occurring mass of mineral matter and are classified into three types – igneous rock, sedimentary rock and metamorphic rock based on how they are formed.
Now that we have learned about rocks, I bet you can answer the questions below.
1. Rocks may be big or small.
A. True
B. False
That’s right! Option (a) is the correct answer. Rocks are in various sizes.
How many types of rocks are there?
A. 2
B. 3
C. 5
Good job! Option B is the correct answer. There are 3 types of rocks – Igneous rock, sedimentary rock and metamorphic rock.
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