What is the difference between plutonic and volcanic igneous rocks

Their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock. They also tend to be very long-lasting. Some of the oldest rocks on Earth are plutonic rocks.

Plutonic rocks form beneath the surface of differentiated planets and large asteroids. They originate from pockets of magma within the crust that can intrude into other rocks. When a large body of molten rock beneath the surface solidifies, it is called a pluton.

Plutonic rocks can be classified based on their composition. A common type of mafic plutonic rock is gabbro. Gabbro commonly forms at mid-oceanic ridges. It can also form wherever there is an especially mafic magma, such as the oceans of molten rock which once existed on the Moon after the large impacts that formed the lunar maria.

Beneath the abyssal plain and slopes of the mid-oceanic ridges, it composes the primary bedrock. Granite is a felsic plutonic rock composing the base of most of the continental crust. Mineralogically, granite contains quartz, various feldspars, and micas. Although there are many rocks that resemble granite, they are not all true granites. Thus, plutonic rocks that are compositionally similar to granite but not identical are referred to as granitoids.

Diorite is the compositional intermediate between granite and gabbro. In addition to true diorites, there are granodiorites which are rock units that are still intermediate but more felsic than mafic. Volcanic and plutonic rocks are both igneous, meaning that they form from molten rock becoming solidified. They can also both be classified based on of their chemical and mineralogical composition. They also both form in geologically active zones such as subduction zones, rift valleys, and mid-oceanic ridges.

Although there are many similarities between volcanic and plutonic rocks, there are also noticeable differences which include the following. Volcanic rocks are igneous rocks that form at the surface of a planetary body from lava extruding out of volcanoes.

They are fine-grained and can be classified based on composition. The most common type of volcanic rock is basalt. Plutonic rocks are igneous rocks that form beneath the surface from solidified magma which once formed subterranean chambers of molten rock.

Like volcanic rocks, plutonic rocks can be classified on the basis of chemical and mineralogical composition. They are also alike in that they occur at geologically active zones. Volcanic rocks and plutonic rocks differ mainly in that volcanic rocks form at the surface of a planet whereas plutonic rocks form beneath the surface.

An example of a mafic rock is basalt, the black rock that forms from lava flows in places like Hawaii. An example of a felsic rock is granite, the light colored rocks that we find in places like the Sierra Nevada mountains in California. Find Your Rock:. Igneous Rocks Igneous rocks are formed from lava or magma.

Fortunately, most igneous rocks are one of three basic compositions: Felsic igneous rocks contain relatively high amounts of silicon, sodium, aluminum, potassium Si, Na, Al, and K and relatively low amounts of iron, magnesium, and calcium Fe, Mg, Ca. Mafic rocks contain relatively low amounts of silicon, sodium, aluminum, potassium Si, Na, Al, and K and relatively high amounts of iron, magnesium, and calcium Fe, Mg, Ca.

Intermediate rocks are what their name sounds like. Their composition is in-between mafic and felsic rocks. Rygel via Wikimedia Commons.

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