Types Of Igneous Rocks
Types Of Igneous Rock
Igneous rocks are mainly classified on basis of their texture an composition.
Granite,A coarse-grained igneous rock composed of K-feldspar, plagioclase, and quartz,
with small amounts of mafic minerals
Diorite,A phaneritic intrusive igneous rock consisting mostly of intermediate plagioclase
feldspar and pyroxene, with some amphibole and biotite.
gabbro, A dark-colored, coarse-grained rock composed of Ca-plagioclase, pyroxene, and
possible olivine, but no quartz.
rhyolite, A fine-grained volcanic rock composed of quartz, K-feldspar, and plagioclase. It is
the extrusive equivalent of a granite.
andesite, Afine-grained igneous rock composed mostly of plagioclase feldspare and fom 25
to 45% pyroxene, amphibole, or biotite, but no quartz or K-feldspar. It is abundant in
mountains bordering the Pacific Ocean, such as the Andes Mountains of South
America, from which this name was derived.
Basalt, A dark-colored, fine-grained, mafic volcanic rock composed of plagioclase (over
50%) and pyroxene. Olivine may or may not be present.
Rocks with Phaneritic Textures
Rocks with Aphanitic Textures
Rocks with Pyroclasti Textures
Ash-Explosive volcanic eruptions of rhyolitic and
andesitic magmas commonly produce large
volumes of fragmental material that are ejected
high into the atmosphere, the fragments range
from dust-size pieces a.k.a ash.
Pumice- is a vescular frothy glass common among
the larger fragments.
Tephra- deposits are composed of shrads of volcanic
glass, pumice, broken phenocrysts, and foreign
The other rock textures are, tuff, pyroclastic-fall tuff,
and ash-flow tuff.
Extrusive Rock Bodies
rocks form from
extrudes onto the
rocks include lava
flow and volcanic
Products of Basaltic Eruptions
Basaltic eruptions are probably the most
common type of volcanic activity on Earth.
The lava is generally extruded from
fractures or fissures in the crust. Basaltic
lavas erupt with temperatures ranging
between 1000 and 12000 C.THE lava can
flow with speeds up to 40 km/hr down
steep slopes, but rates of 20 km/hr are
considered unusually rapid. EX, the
basaltic lava on Galapagos islands move
an average of 170 m/hr.