Chapter 3 – Rocks: Materials of the Solid Earth
I. Rock cycle
A. Shows the inter-relationships among the three rock types
B. Earth as a system: the rock cycle
1. Magma
a. Crystallization
2. Igneous rock
a. Weathering
b. Transportation
c. Deposition
3. Sediment
a. Lithification
4. Sedimentary rock
a. Metamorphism
5. Metamorphic rock
a. Melting
6. Magma
C. Full cycle does not always take place owing to "shortcuts" or interruptions; for example,
1. Sedimentary rock melts
2. Igneous rock is metamorphosed
3. Sedimentary rock is weathered
4. Metamorphic rock weathers
II. Igneous rocks
A. Form as magma cools and crystallizes
1. Rocks formed inside Earth
a. Called plutonic or intrusive rocks
2. Rocks formed on the surface
a. Formed from lava (a material similar to magma, but without gas)
b. Called volcanic or extrusive rocks
B. Crystallization of magma
1. Ions arrange themselves into orderly patterns
2. Crystal size is determined by the rate of cooling
a. Slow rate produces large crystals
b. Fast rate produces microscopic crystals
c. Very fast rate produces glass
C. Classification is based on the rock's texture and mineral constituents
1. Texture
a. Size and arrangement of crystals
b. Types
1. Fine-grained—fast rate of cooling
2. Coarse-grained—slow rate of cooling
3. Porphyritic (two crystal sizes)— two rates of cooling
4. Glassy—very fast rate of cooling
2. Mineral composition
a. Explained by Bowen's reaction series, which shows the order of mineral
crystallization
b. Influenced by crystal settling in the magma
D. Nomenclature of igneous rocks
1. Granitic rocks
a. Composed almost entirely of light-colored silicates—quartz and feldspar
b. Also referred to as felsic: feldspar and silica (quartz)
c. High silica content (about 70 percent)
d. Common rock is granite
2. Basaltic rock
a. Contain substantial dark silicate minerals and calcium-rich plagioclase feldspar
b. Also referred to as mafic: magnesium and ferrum...