Rocks Flashcards
What are igneous rocks?
Form as molten rock cools and solidifies
What is magma?
Intrusive rocks or plutonic rocks
What is lava?
Extrusive rocks or volcanic rocks
What are extrusive igneous rocks?
Magma that exists or cooled above ground
What are intrusive igneous rocks?
Magma that cooled below ground surface
What are the three components of magma?
- Liquid portion = melt
- Solids, if present, silicate materials
- Volatiles = dissolved gases in melt
What determines the texture of igneous rocks?
Rate of cooling
1. Slow rate = fewer but larger crystals
2. Fast rate = many small crystals
3. Very fast rate = forms glass
What are the different igneous textures?
Aphanitic
Porphyritic
Phaneritic
Glassy
Pyroclastic
Pegmatitic
What is an aphanitic texture?
Fine-grained
Rapid rate of cooling
Microscopic crystals
What is a phaneritic texture?
Coarse-grained
Slow cooling
Large, visible crystals
What is a porphyritic texture?
2 stages of cooling
Large crystals embedded in smaller crystals
What is a glassy texture?
Very rapid cooling
Results in obsidian
What is a pyroclastic texture?
Fragmental appearance
Formed by violent volcanic eruptions
What is a pegmatitic texture?
Exceptionally coarse-grained
Forms in late stages of crystallization of magmas
What are the different igneous compositions?
Felsic
Intermediate
Mafic
Ultramafic
What determines igneous composition?
Silica content
What is a felsic composition?
Silica rich & iron poor
Nonferromagnesian silicates
Major constituent of continental crust
What is an intermediate composition?
More iron & less silicate
> 25% ferromagnesian silicates
53-65% silica
What is a mafic composition?
More iron & magnesium
Ferromagnesian silicates
Silica poor (45-52%)
Comprise ocean floor & volcanic islands
What is an ultramafic composition?
Rare
Entirely ferromagnesian silicates
< 45% silica
How does magma originate?
Heat
Pressure
Volatiles
How do sedimentary rocks form?
products of mechanical & chemical weathering
What are the types of sedimentary rocks?
Detrital rocks
Chemical rocks
What are detrital rocks?
Transported sediment as solid particles
What are chemical rocks?
Sediment once in solution
What are types of detrital rocks?
Shale
Sandstone
Conglomerate & breccia
What are types of chemical rocks?
Limestone
Dolostone
Chert
Evaporites
Coal
What are the classifications of chemical rocks?
Clastic
Nonclastic
What is a clastic rock?
Discrete fragments & particles
What is a nonclastic rock?
Pattern of interlocking crystals (resemble igneous rocks)
What are the types of sedimentary structures?
Bedding planes
Cross-bedding
Graded beds
Ripple marks
Mud cracks
What is metamorphism?
Transition of one rock into another by temperatures and/or pressures
What are the types of metamorphism?
Contact metamorphism (heat)
Dynamic metamorphism (pressure)
Regional metamorphism (heat and pressure)
What are the agents of metamorphism?
Heat
Pressure & stress
Fluids
Parent rock
What are the two types of pressure?
Lithostatic
Differential
What is lithostatic pressure?
Weight of the overlying rocks
What is differential pressure?
Pressures that are not equal on all sides
What are the metamorphic textures?
Foliated
Non-foliated
What is texture?
Size, shape, & arrangement of mineral grains
What is foliation?
Planar arrangement of mineral grains
What are the types of foliated textures?
Slaty cleavage
Schistosity
Gneissic
What are types of foliated rocks?
Slate
Phyllite
Schist
Gneiss
What are the types of non-foliated rocks?
Marble
Quartzite
What are the different metamorphic environments?
Continental
Transformational
Marine
