Want this question answered?
Some do. These are called extrusive igneous rocks. However a large portion of igneous rocks form beneath the surface. These are intrusive igneous rocks.
If the magma cools on the surface of the crust, it is called extrusive igneous rock, such as pumice, basalt or rhyolite. If the magma cools inside the crust, it is called intrusive igneous rock, such as granite.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.
Extrusive, Igneous rocks possibly lavas or ignimbrites.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.
Igneous.
Some do. These are called extrusive igneous rocks. However a large portion of igneous rocks form beneath the surface. These are intrusive igneous rocks.
Intrusive or extrusive are terms given to igneous rocks which describe where the rock cooled and formed, since this plays an important role in the cooling time of the rock and therefore grain size of the rock. Intrusive rocks are those that cool from magma before it reaches the surface of the earth (they form inside the earth, hence the term intrusive). Extrusive rocks form by erupting or "extruding" at the surface and cooling. Intrusive rocks take a long time to cool because the surrounding rocks act as a kind of blanket and keep it warm longer, so crystals are generally large, where extrusive rocks cool quickly being exposed to air, wind, and rain, so crystals are generally small.
Igneous rocks are formed from the cooling and solidifying of magma. The resulting rock can be instrusive (magma cooling within the crust) and extrusive (lava cooling on the surface). The most common kind of rocks are Granite (intrusive) and Basalt (extrusive).
If the magma cools on the surface of the crust, it is called extrusive igneous rock, such as pumice, basalt or rhyolite. If the magma cools inside the crust, it is called intrusive igneous rock, such as granite.
Extrusive igneous rock is one of two different types of igneous rocks. The other kind is intrusive igneous rock. Intrusive igneous rock is formed when magma in Earth's lithosphere cools and hardens. Extrusive igneous rock is formed when lava on Earth's surface cools and hardens.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.
Extrusive igneous rocks such as basalt or rhyolite.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.
Igneous: These rocks are volcanic in nature. They are split into two categories in where they cool/crystallize: intrusive (internal) and extrusive (external). Intrusive volcanic rocks cool slowly, so they contain (usually) large crystals, like granites. Extrusive rocks are quite the opposite, in which they cool very quickly. This is where you get your obsidian glass and basalts. Sedimentary: These rocks are depositional and categorized by the kind of sediment it is made up of. Metamorphic: This can be the offspring rock of either a morphosed igneous or sedimentary rock. This metamorphism is accomplished by heat and/or pressure, and during a great length of time.