What is the difference between the two types of igneous rocks?
The two main categories of igneous rocks are extrusive and intrusive. Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.
What is the most abundant sedimentary rock?
Shale, any of a group of fine-grained, laminated sedimentary rocks consisting of silt- and clay-sized particles. Shale is the most abundant of the sedimentary rocks, accounting for roughly 70 percent of this rock type in the crust of the Earth.
Which igneous rock is the most common type found in continental crust?
Continental crust is mostly composed of different types of granites. Geologists often refer to the rocks of the continental crust as “sial.” Sial stands for silicate and aluminum, the most abundant minerals in continental crust.
Why continental crust is granite?
Continental crust is indeed “granitic”, and has the general composition typical of granitic rocks, made up of mostly aluminium silicates (the SiAl). These intermediate and acid igneous rocks (like granite, andesite and rhyolite) then form the basic materials from which continent-derived sediments are formed.
What do igneous rocks have in common?
Origin. Igneous rocks (derived from the Latin word for fire, ignis) can have very different mineral backgrounds, but they all share one thing in common: they formed by the cooling and crystallization of a melt.
What are the characteristics of intrusive igneous rocks?
Intrusive rocks are characterized by large crystal sizes, i.e., their visual appearance shows individual crystals interlocked together to form the rock mass. The cooling of magma deep in the Earth is typically much slower than the cooling process at the surface, so larger crystals can grow.
How do you classify igneous rocks?
Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic, and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained (microscopic crystals) or glass ( …