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Difference between Volcanic Rocks and Plutonic Rocks

Volcanic rocks and plutonic rocks both are igneous rocks. Although both are igneous rocks, they are different from each other in terms of their colour, formation and size of granules. Let us how they differ from each other!

Volcanic Rocks:

Volcanic rocks are formed above the ground from the hot magma that erupts from a volcano onto the surface of the Earth. The hot magma is called lava when it comes out onto the Earth's surface. As the lava cools down it starts changing into crystals. The crystals continue to grow as long as lava keeps losing heat and cools or solidifies.

Volcanic rocks are formed quickly as the lava cools quickly so their crystals tend to be very small and thus they are fine-grained. These rocks can be made of ash, which is a pulverized rock blown into the air. The volcanic rocks are named after volcanoes as they are formed of lava that erupts from the volcanoes. The volcano is named after Vulcan which is a Roman God of fire and metalworking. Some common examples of volcanic rocks are basalt, rhyolite etc.

Plutonic Rocks:

Plutonic rocks are igneous rocks that are formed underground or deep under the Earth's surface. They are intrusive igneous rocks with coarse grain size and are formed due to the intrusion or insertion of magma between other rocks below the surface of the Earth. This magma cools down or solidifies below the surface to form plutonic rocks. Plutonic rocks are coarse-grained as they are formed slowly that allows the formation of large crystals before the magma solidifies into a rock.

Plutonic rocks are one of the most commonly found rocks on the Earth. They serve as a foundation for our continents and mountain ranges. They can be divided into acidic, basic and ultra-basic types on the basis of their mineral and chemical composition. Some common examples of plutonic rocks are granite, diorite, aplite, pegmatite, syenite etc

Based on the above information, some of the key differences between volcanic and plutonic rocks are as follows:

Volcanic Rocks Plutonic Rocks
Volcanic rocks are igneous rocks that are formed above the ground from the lava. Plutonic rocks are igneous rocks that are formed deep under the Earth's surface from the magma.
They are formed from the hot lava that erupts from the volcano onto the surface of the Earth. They are formed from the hot magma that penetrates into other rocks below the Earth's surface.
It is generally a dark coloured rock. It is generally a dark grey coloured rock.
The lava cools down quickly so these rocks are fine-grained. The magma cools down slowly so these rocks are coarse-grained as large crystals could be formed before the magma solidifies.
The volcanic rocks are basalt, gabbros. The plutonic rocks are granite, diorite.
It is hard and heavy so often used for building roads. It is often used as building stone.
The volcanic rocks are formed quickly as compared to plutonic rocks because the lava cools and solidifies quickly as it is on the Earth's surface that allows it to lose heat quickly to the surroundings. The rate of formation of plutonic rocks is very slow. It may take millions of years to form a plutonic rock as magma under the Earth's surface takes more time to cool down.
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