Welcome to GLG101C Introduction to Geology
Fall 2004
Professor James Tyburczy
Department of Geological Sciences  

Class Notes Chapter 5

Check out the Igneous Rocks Tour from California State University Long Beach for good pictures and even a quiz.

Here is the Rockhounds Information Page, more information and sites on rocks and minerals



Formed from the cooling and solidification of magma - molten silicate, high temperature (1200 deg C)

Classification of igneous rocks:

How do we know about cooling rates of rocks?

Intrusive rocks - Evidence for crystallization below Earth's surface

Chemical classification of igneous rocks - (see Table 5.2 and Figure 5.4) - chemical composition ranges (SiO2 content 70 % for granite, 50% for basalt), characteristic minerals, plagioclase feldspar composition, temperature, viscosity, intrusive and extrusive rock names

Origin of magma

Magmatic Differentiation - why do magmas have such a wide range of compositions?

Controls on types of igneous rocks

Intrusive bodies - large or small, characteristic shape, deep or shallow, structural relation to surrounding rocks - dike, sill, pluton, batholith

Other rock textures:

Global Distribution of Plutonic Rocks

Controls on types of igneous rocks - plate tectonic settings - divergent margins, convergent margins, intra-plate (hot spots)


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©2004, James A. Tyburczy, Department of Geology, Arizona State University
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Last update 9/8/2004