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Geology Test 1


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Catastrophism is...
The concept that earth was shaped by catastrophic events of a short-term nature
Hutton's idea of Earth's uniformitarianism is that...
physical, chemical and biological laws that operated in the past also operate today
Law of Superposition
In any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.
3 Types of Rock
Structure of the Earth (3 main components)
1. Crust
2. Mantle
3. Core
5 Main Layers of the Earth
1. Lithosphere
2. Asthenosphere
3. Mesosphere
4. Outer Core
5. Inner Core
Mantle (properties)
Composed of dense materials
(olivene, pyroxcene)
Crust (properties)
The thin, outermost layer of Earth.
-Divided into Oceanic and Continental crust
Oceanic Crust (properties)
- 1-10 km thick (avg. 5 km)
- Relatively heavier; more dense
- Made of Basalt
Continental Crust (properties)
- 10-70 km thick (avg 35 km)
- Relatively lighter; less dense
Core (properties)
The innermost layer of earth based on composition
-Largely an iron-nickel alloy with small amounts of oxygen, silicon, and sulfur
Lithosphere (properties)
The rigid outer layer of earth, including the crust and upper mantle
Asthenosphere (properties)
- Layer beneath the lithosphere
- Flows, or easily deforms (still solid)
Mesosphere (properties)
The part of the mantle that extends from the core-mantle boundary to a depth of 660 km
- aka the "lower mantle"
Outer Core (properties)
The convective flow of metallic iron that generates Earth's magnetic field
- Liquid layer
Inner Core (properties)
The solid innermost layer of earth
- Radius of 1216 km
How do people believe the earth formed?
After the "big bang", rotating debris collided and melted together
2 Types of Igneous Rocks
Intrusive - rocks that form inside the Earth (plutonic)

Extrusive - Rocks that form on the outside (volcanic)
Textures of Igneous Rocks
Vesicles - small, hollow pockets of air in the rock

Glassy - represents very small grains of quickly cooled magma

Pyroclastic - welded fragments of igneous rocks

Pegmatite - very large mineral grains
3 general textures that represent cooling rates
Aphanitic - fine grained, small crystals. Indicates that rock is extrusive (cooled quickly).

Porphyritic - crystals swimming in sea of fine grained crystals. (between aphanitic and phaneritic)

Phaneritic - large grained, bigger crystals. Indicateds that rock is intrusive (had more time to cool)
Composition of Igneous Rocks
-Ultramafic/mafic rocks- Have large quantities of ferromagnesium minerals

-Felsic Rock- Have large number of nonferromagnesium minerals

-Intermediate- mixed proportions of minerals
2 Types/Groups of minerals
Ferromagnesium minerals - darker, denser minerals
-olivene, pyroxenes (augite), amphiboles (hornblende)

Non-ferromagnesium minerals - lighter, less dense minerals
-micas/clays, framework silicates (feldspar, quartz, orthoclase)
Definition of minerals
Any naturally occuring, inorganic solid that possesses an orderly internal structure and definite chemical composition.
Ionic Bond/Covalent Bond
Ionic bond - one or more valence electrons are transferred from one to another

Covalent bond - sharing of electrons (usually gases)
How crystals form
1. Evaporation of a liquid
2. From magmas
3. Previous minerals that make new ones
- Silicon-oxygen tetrahedron
- 4 oxygens surround 1 silicon atom
Olivene Group
Tetrahedra bond with metal cations
Solid Substitution
When 2 atoms of a similar size and charge can "substitute" into crystal at various proportions

1. Tetrahedra
2. Single Chain
3. Double Chain
4. Sheet
1. Si:O ratio is 1:4
2. Share one oxygen; 1:3 ratio
3. Share two oxygen; 1:2 ratio
4. Share three oxygen

-Tetrahedra are the basic building blocks for the crystal structure

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