Download Ch 4 Igneous Rocks

Ch 4 Igneous Rocks
A. Rocks and The Rock Cycle
1. _____________ - group of minerals bound together in some way
2. _______________ - cooling and hardening of hot molten rock
3. ________________ - Hardening and cementing of layers of sediments
4. ___________________ - changed by heat and pressure
5. ____________________ - transformation from one rock type to another
B. Igneous Rocks: The Origin of Magma
1. Processes that form magma
a. Rising __________________ - in crust - temp rises 300 C / km of depth
b. Decreasing ____________________ - pressure release melting
c. Addition of ___________ - wet rock melts at a lower temp than a dry rock
2. Environments of magma formation
a. ___________________________ - plates spread apart - asthenosphere rises,
pressure drops and forms basaltic magma - ocean basins - mid oceanic ridges
b. ___________________ - volcanically active place at the Earth’s surface
directly above a mantle fume - Yellowstone National Park, Hawaii Islands
c. ________________________ - addition of water - subducting plates volcanoes of Pacific Northwest, granite cliffs of Yosemite, and Andes Mountains
3. Characteristics of magma
a. Temperature varies from ________ C to ___________ C
b. Chemical composition - silicate magmas- ____ and _____
(1) Basaltic magma - more ______and ______
(2) Granitic magma - more ______, _______, and ______
c. Behavior - when rock melts it expands 10%
C. Classification of Igneous Rocks
1. Recognizing Igneous Rocks
a.
___________________ (Volcanic) - magma erupts on surface - lava
b. ___________________ (Plutonic) - magma solidifies within crust
2. Kinds of Magma
a. _________ - light colored, high silica rock (thick) Feldspar and silica
b. __________ - dark colored, low silica rock (thinner) Mg and Fe
Ex. Granite
Ex. Basalt
c. ____________ - very high concentration of Mg and Fe
d. _____________ - composition between granite and basalt
2. Texture - depends on _________, shape, and arrangement of mineral grains, or crystals
a.
How fast it cools- slow cooling produces larger crystals Ex.
Fast cooling produces smaller crystals Ex.
Very fast cooling produces glassy
Ex.
b.
Amount of __________ dissolved - more gas smaller crystals
c. Porphyritic texture - two different textures
____________________ - Larger crystal embedded in fine-grained matrix
D. Naming Igneous Rocks
Kinds of Magma
Felsic (light colored)
Intermediate
Mafic (dark colored)
Ultramafic
Coarse Grain
Fine Grain
Glassy
E. Common Igneous Rocks
1. Granite and Rhyolite
Granite - most common ________________________ igneous rock - basement rock
- forms mountains - Rockies, Adirondacks, Black Hills
2. Basalt and Gabbro
Basalt - most common rock on ______________________ and forms basalt plateaus
Gabbro - uncommon, found in deeper parts of _______________
3. Andesite and Diorite
Andesite - Andes Mtns - S. America
Diorite - Deep under Andes Mtns
4. Peridotite - __________ mantle
F. Partial Melting
1. ________________________ Melting - when you heat a rock, the minerals with the
lowest melting point melts first
2. In general, minerals with the highest silica content melt at the lowest temperature
3. ____________________ reaction series - when magma cools:
Crystallize first - highest temperature - lowest % Si