Classi
igneous_rock_diagram.GIF
How Igneous Rocks Form
fying Igneous Rocks
By: Prarthana Venkatesh and Yuki Yamammoto 7A

Igneous rocks are intrusive or extrusive, it all depends on HOW they are formed. The magma from which they form is also use
classifying_diagramm.GIF
Classifying Igneous Rocks Diagram
d to classify igneous rocks. The type of magma that cools to form an igneous rock determines some properties of that rock, like the mineral composition, density, color and melting temperature.

Bas
altic Rocks

Basaltic igneous rocks form from magma that is rich in iron and magnesium, and poor in silica. The iron and magnesium give it the dark color. They are dense, and dark colored. Basaltic lava is fluid, and flows freely from volcanoes,especially in Hawaii. Basalt forms on the surface of the Earth, it is an extrusive rock.
Basaltic_Rock.upload.prarthana.jpg
Basalt
gabbro.upload.prarthana.jpg
Gabbro

scoria.upload.prarthana.jpg
Scoria

Granite Rocks
Granite Igneous rocks form from magma that is thick, stiff and contains lots of silica, less of iron and magnesium. They are light colored, and have a lower density than basaltic rocks. Because granitic magma is stiff, it can build up a lot of gas pressure, which is released explosively, in volcanic eruptions. Granite forms from magma, below the Earths surface.
obsidian.upload.prarthana.jpg
Obsidian

Granite_Rock_.upload.prarthana.jpg
Granite

rhyolite.uploaed.prarthana.jpg
Rhyolite

pumice.upload.prarthana.jpg
Pumice

Andesitic Rocks
The mineral compositions of Andesitic Rocks are between basaltic and granite. Many volcanoes around the Pacific Ocean are made up of Andesitic Rocks. These volcanoes can erupt violently, like volcanoes that erupt granitic magma.
diorite.upload.prarthana.jpg
Diorite

Andestic_Rock.upload.prarthana.jpg
Andesite


Links to Related Pages
Igneous Rocks
Rock Cycle


Bibliography
Information:
http://library.thinkquest.org/J002289/igneous.html
http://www.edu.pe.ca/southernkings/igneousjj.htm
http://www.fi.edu/fellows/fellow1/rocks/create/igneous.htm
http://www.tulane.edu/~sanelson/geol111/igneous.htm
http://geology.com/rocks/igneous-rocks.shtml
http://www.abheritage.ca/abnature/geological/photos/class_igneous_rocks.GIF
http://www.vtaide.com/png/images/rockCycle.jpg

Pictures:
http://upload.wikimedia.org/wikipedia/commons/archive/18/20080122084456!Scoria_Macro_Digon3.jpg
http://geology.com/rocks/pictures/gabbro.jpg
http://geology.com/rocks/pictures/quartz-diorite.jpg
http://geology.com/rocks/pictures/rhyolite.jpg
http://www.swisseduc.ch/stromboli/glossary/icons/pumice_2.jpg
http://geology.com/rocks/pictures/obsidian.jpg

Books:
Glencoe Earth Science Textbook