how r igneous rocks formed?

Answer 1

Igneous rocks are formed from molten magma or lava. The word, igneous means "fire". All igneous rock starts deep in the earth as hot, molten magma. If the magma cools and hardens inside the earth it is called "intrusive" rock. These rocks cool slowly and have large crystals. When the magma comes out of the earth's crust through a volcano, it is called "extrusive". It cools off quickly, and the crystals that form are very small. Molten, or hot, liquid rock is called MAGMA when it is still inside the earth, but once it comes out through a volcano it is called LAVA.

For Eample :granite , scoria , pumice

Igneous rocks are formed from the solidification of magma, which is a hot (600 deg.C - 1300 deg.C, or 1100 deg. - 2400 deg. F) molten or partially molten rock material.

Magma is thought to be generated within the asthenosphere (the layer of partially molten rock underlying the Earth's crust) at a depth below about 60-100 kilometers (40-60 miles). Because magma is less dense than the surrounding solid rocks, it rises toward the surface. It may settle within the crust or erupt at the surface from a volcano as a lava flow. Rocks formed from the cooling and solidification of magma deep within the crust are distinct from those erupted at the surface mainly owing to the differences in conditions in the two environments. Within the Earth crust the temperatures and pressures are much higher than at its surface; consequently, the hot magma cools slowly and crystallizes completely. The slow cooling promotes the growth of minerals large enough to be identified visually without the aid of a microscope . On the other hand, magma erupted at the surface is chilled so quickly that the individual minerals have little or no chance to grow. As a result, the rock is either composed of minerals that can be seen only with the aid of a microscope or contains no minerals at all (in the latter case, the rock is composed of glass, which is really a viscous, non-crystalline liquid). This results in two groups of igneous rocks: (1) plutonic or intrusive igneous rocks that solidified deep within the earth and (2) volcanic, or extrusive, igneous rocks formed at the Earth's surface.

Igneous processes have been active since the formation of the Earth some 4.6 billion years ago.

Answer 2

<-- has a geology degree... everyone is right- volcanic activity causes the formation of igneous rocks. not necessarily volcanoes though, a good sill or dike will also harden into igneous rocks, really any volume of cooled magma- whether it cools in the ground or above ground will become igneous.

Answer 3

they were one of the first rocks on earth mostly created through volcanic activities which means that when a volcano erupts and after awhile, it cooled down and formed igneous rocks...

Answer 4

As volcanic rock cools.

Answer 5

a volvano erupts, when the lava cools a rock is form, this is ignoues rock

http://www.fi.edu/fellows/fellow1/oct98/create/igneous.htm

Answer 6

By volcanic material.

Answer 7

i cant answer your question but i hope there is someone here who can