How do intrusive and extrusive igneous rocks form?

Answer 1

Igneous rocks are formed when magma crystallizes and cools into a solid form. There are two types of igneous rocks--intrusive igneous rocks and extrusive igneous rocks.

Intrusive:

Intrusive igneous rocks are formed when the melted rock (magma) slowly rises toward, but does not reach the surface. As these pockets of magma cool slowly underground, minerals crystallize and the magma solidifies, becoming intrusive igneous rock, like granite and gabbro.

Extrusive:

Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the Earth's surface. When magma appears above the surface, it is called lava. Extrusive igneous rocks are formed as the lava cools above ground. Examples of extrusive igneous rock are basalt, rhyolite, pumice, and scoria.
igneous rocks are formed by lava
Well When melted rock cools quickly, it hardens before any mineral crystals can grow large. as a result, igneous rocks that form above ground have small or no crystals :)
Igneous Rocks are made of magma and lava because it comes out of a volcano
From volcanoes.
from lava cooling.
Molten rock cools and turns solid.

Answer 2

Intrusive and extrusive are formed when lava or magma solidifies. Intrusive igneous rocks form when magma cools beneath the Earth's crust, while extrusive igneous rocks form when lava cools above the Earth's crust.

Answer 3

Intrusive igneous rocks form inside the Earth's crust from slowly cooling magma. Extrusive igneous rocks form on the Earth's surface from quickly cooling lava. The rate of cooling affects the crystal size and texture of the rock.

Answer 4

Extrusive rocks are... extruded... onto the surface as the lava that we all think of. It cools fairly quickly, into rocks with fairly small crystals (might need a magnifying lens to see them). The exact chemistry of the parent magma will determine the type of rock. Oceanic volcanoes are generally basaltic (mafic or ultramafic), continental are generally granitic (felsic or intermediate). They're put down in "relatively thin" layers

Intrusive rocks cool for thousands of years beneath the surface in huge plutons or batholyths. This allows them to grow very large crystals (easily seen by the unaided eye). These intrusive rocks are almost always granitic-type rock.

My sources are:

from my science teacher who worked at the science museum

yahooanswer.com

ask.com

wikipedia the free encyclopedia

I hope this information helped. Good luck!

Answer 5

Both are formed from the crystallization of minerals caused by the cooling of magma. Intrusive igneous rocks cooled below the surface of the planet, however, and generally display larger crystals due to the increased amount of time spent at mineral crystallization temperatures from the insulating effect of surrounding material. Extrusive rocks are formed from magma at or above the surface of the planet, and generally display smaller mineral crystals, or no crystals at all, because of the rapid cooling environment in which they form. Chemically, an intrusive and extrusive rock could be identical, the only difference being the size of the mineral crystals they contain.

Answer 6

cooling lava at the earths surface