Earth Systems 3209 Review Sheet
Chapter 3 - Igneous Rocks
Terms
Rock Cycle
Lava
Intrusive
Volatiles
Glass
Phaneritic
Mafic (basaltic)
Rhyolite
Andesite
Gabbro
Geothermal Gradient
Bowen’s Reaction Series
Igneous Rocks
Extrusive
Plutonic
Crystallization (igneous)
Aphanitic
Porphyritic
Intermediate (andesitic)
Obsidian
Diorite
Tuff
Decompression melting
Magma
Volcanic
Melt
Texture
Vesicular Texture
Felsic (granitic)
Granite
Pumice
Basalt
Volcanic Breccia
Topics
p. 60-61 – Understand the nature of igneous rocks; how they are formed, their basic properties, terms
used to describe their origin, and the importance of crystallization in determining the type of rock
formed.
p. 62 – Know that the two main factors to consider when classifying igneous rocks are mineral types and
texture (crystal size).
p. 62-65 – Be able to describe the differences between the following texture types: aphanitic (fine
grained), phaneritic (coarse-grained), porphyritic (large crystals surrounded by small), and glassy.
Understand that texture is caused by cooling rate of magma (slower cooling = larger crystals = coarser
grain)
p. 65-69 - Describe how mafic igneous rocks differ from felsic igneous rocks based on chemical
composition (see Fig. 3.7 on p. 67). Felsic rocks contain large quantities of quartz and potassium feldspar
while Mafic rocks contain large quantities of pyroxene and olivine. Know the importance of silica
content as an indicator of rock type (high silica = Felsic). Melting point and colour are also affected by
silica content.
p. 70-71 – Know the major features of the felsic rocks granite, rhyolite, obsidian, and pumic.
p. 72 – Know the major features of the intermediate rocks andesite and diorite.
p. 73 - Know the major features of the mafic rocks basalt and gabbro
p. 74 - Know the major features of the pyroclastic rocks tuff and volcanic breccias
p. 75-77 – Understand how three key factors control how and when magma forms: heat, pressure, and
the presence of volatiles. Use this understanding to explain what is happening in Figs. 3.20 and 3.21
p. 78-80 Know that Bowen’s Reaction series describes the sequence that minerals crystallize from
magma as it cools down thus describing under what conditions certain igneous rocks will form.