149 Cards in this Set
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Historical Geology
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Understanding the origin of the Earth and its development over time.
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Physical Geology
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Study of materials composing the Earth.
Understanding the processes operating on and beneath Earth's surface.
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Catastrophism
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-BIG
-landforms formed by sudden global catastrophies
-meteorite impacts
-worldwide floods
-global earthquakes
-global volcanic activity
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How old is the Earth?
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4.6 Billion years
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What is relative age dating?
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-Placing geological events in order without knowing their numerical age.
-Based on relative age dating principles.
-Began as a simple hypothesis.
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Hypothesis
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Answering questions in the most scientific way possible
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Theory
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A well-tested, widely accepted, and considered to be the best explanation of observed facts.
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Differentiation
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As Earth cooled and changed from the molten homogeneous mixture it once was to the Earth that we know today, similar elements in the molten mixture begin to pool together.
-Heavy elements = Down to core
-Light elements = Up to crust
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Earth's crust
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Rocky outer skin. Thinnest layer.
"floats" on the upper mantle.
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Continental crust
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-Thickness: 25 miles
-Composition: Many rock types
-Age: Up to 4GA (Billion) in some places
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Oceanic crust
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-Thickness: 5 miles
-Composition: 1--Basalt
-Age: no more than 180GA (Billion)
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Mantle
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Solid, rigid layers
82% of Earth's volume
Divided into upper and lower
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Core
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Made up of nickle and alloy
Divided into inner and outer
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Inner Core
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Solid.
Source of internal heat.
(Sphere)
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Outer Core
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Liquid.
Provides magnetic field.
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Mountain belt areas
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-Long, narrow, high elevation features
-typically along continental margins
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Stable interior areas
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-extensive, flat, stabel areas that have eroded heavily to sea level.
-anything NOT a mountain
-interior of continents
-"quiet" regions
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Features on the ocean floor
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Volcano chains, canyons, plateaus, and flat plains...
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Continental margin
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Portions of the sea floor are adjacent to continents.
Includes:
Continental Shelf
Continental Slope
Continental Rise
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Deep ocean basin
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Are between continental margin and oceanic ridges.
Includes:
Abyssal plains
Deep-ocean trenches
Seamounts
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Abyssal Plains
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Extremely flat features on ocean floor
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Deep-ocean trenches
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Extremely deep depressions
(up to 36000 ft)
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Underwater volcanoes
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Underwater volcanoes
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Oceanic Ridges
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Most prominent feature on the ocean floor
Continuous feature covering the ocean floor. ~43000 miles long
Composed of fractured, uplifting igneous rock (basalt)
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Rock types
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Most common and abundant material on Earth.
Appearance is determined by the minerals that compose it
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Igneous
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Formed when molten rock cools and solidifies
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Sedimentary
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Lithified sediment grains (smaller fragments of rock)
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Metamorphic
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Forms when intense heat and pressure change pre-existing rock
(of any type)
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James Hutton
(1726 - 1797)
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Father of Modern Geology
Theory of Earth in 1795
First to prove geological process occurs over extremely long periods of time
"What more can we require? Nothing but time"
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Discovery of Radioactivity: 1896
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Discovered by Henry Becquerel
Radioactivity wasn't used to determine numerical dates until 1905
Methods constantly refined
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Brittle outer layer of the Earth
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Lithosphere
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Mineral
(according to geologist)
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A naturally occurring, inorganic, solid, compound having an internal crystalline structure and characteristic chemical compound
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Naturally ocurring
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-formed natural, geological processes.
-synthetic gems are NOT minerals
-"if you cant dig it out of the ground, its not a mineral"
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Inorganic
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-by definition, all minerals are inorganic
(not alive, never was, & never will be)
-Modern minerals include an organic class made by living things
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Solid
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-Minerals are solids on Earth's surface
-Solid H2O (ice) is a mineral.
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Internal crystalline structure
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-atoms are arranged in an orderly, repetitive pattern.
-orderly arrangements result in regularly-shaped objects, or crystals
-each mineral type has a unique crystalline structure.
-crystal structure influences a mineral's properties
-atom arrangement determines mineral properties
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Chemical composition
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-composed of one or multiple elements
-minerals are expressed by their chemical formulas
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The Main Eight
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Sodium -Iron
-Magnesium -Aluminum
-Potassium -Silicon
-Calcium -Oxygen
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Atom
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-composed of a nucleus consisting of protons + neutrons
-Protons = + (positive)
-Neutrons have no net electric charge (neutral)
-surrounded by orbiting electrons
-electrons = - (negative)
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Electrons
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-move around the nucleus in regions called principle shells
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Principle shells
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-each shell holds a certain number of electrons
-outermost shell contains valence electrons
-atoms bond (or dont) depending on the number of valence electrons
-a valence shell becomes full when it contains 8 electron
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Chemical bonding
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-when a shell is not full, an atom will transfer or share electrons with others to fill its valence shell.
-If an atom does not have a full valence shell, it will seek out a match
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Chemically inert
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an atom with full valence shells
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Iconic bonding
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-when an atom donates its electron(s) to another atom, it gains a positive (+) charge.
-atoms receiving the electron(s) will gain a negative (-) charge.
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Covalent bonding
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-When shells overlap, atoms begin to share electrons.
-more overlap = more shared electrons = stronger bonds
-extremely hard and super high melting points
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Metallic bonding
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-Shared electrons are free to move from atom to atom
-type of covalent bond.
-positively charged and from the structure of a mineral
-because electrons are not attached to individual atoms, the metal ions can condense to minimize space.
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Van der Waals Forces
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-What holds together phyllosilicates
-produced between layers of atoms during crystallization
-Polarization causes the same effect in neighboring layers
-Weakest type of bond. -soft and greasy feeling
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Hydrogen bonding
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-Occurs only for H because it only has one electron
-When H shares its electron,it becomes positive and easily bonds with Oxygen
-H2O is the base molecule for this type of bond.
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Which two types of chemical bonding are NOT caused by the actions of valence electrons??
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Van der Waals forces
-Hydrogen Bonding
-Rely on weak electrostatic forces
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What is crystallization?
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-Mineral crystals are formed ______
-Molecules chemically bonding to form a solid with an internally orderly structure.
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H2O Solutions
(Crystallization)
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-Aqueous solutions contain dissolved ions.
-When solutions evaporate, ions become more concentrated until a saturation limit is reached.
-Once saturated, atoms bong together to form minerals
-Mineral crystals will precipitate out of the solution
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Temperature Change
(Crystallization)
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-Atoms in magma/lava are very mobile due to high temperatures.
-upon cooling, atoms slow down and begin to combine to form minerals.
-Decrease of temperature causes the liquid to crystallize
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Biological processes
(Crystallization)
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-Organisms can produce substantial quantities ot organic mineral matter.
-Marine critters secrete shells composed of calcite and aragonite (Both CaCo3)
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What is a polymorph?
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-Chemical composition is the same, but crystalline structure is different
-Occurs when identical molecules crystallize in different environments and actually produce different minerals
-allow an interpretation of the conditions the mineral was created and/or has endured
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Example of a polymorph
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KalSi3O2 - Potassium feldspar (Kspar)
-Low temp: Microcline
-Med temp: Orthoclase
-High temp: Sanidine
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Luster
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-How light is reflected from a mineral's surface
-Metallic vs. non-metallic
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Transparency
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Mineral's abilitly to transmit light
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Opaque
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no light transmitted
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Translucent
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light but no image transmitted
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Transparent
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Both light and an image transmitted
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Color
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-Mineral's appearance in relflected light
-NOT a good way to ID minerals
-the same mineral can have man different colors, as well as minerals can share the same color.
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Streak
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-Mineral's color in its powdered form
-Not always the same color as the in-hand sample
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Crystal habit
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-The common characteristic shape of a crystal
-Helpful in ID of minerals that "had room to grow
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Tenacity
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-Mineral's behavior when it is deformed or broken
(Resiliency)
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Brittle
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-Breaks or powders easily
-Most minerals have this quality
-Rigid, unyielding minerals have this quality
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Malleable
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-May be pounded into thin sheets
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Ductile
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-Can be formed into a wire
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Sectile
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-Can be easily cut by a knife
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Elastic
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-If bent, the mineral will spring back to its original position after the stress is released
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Flexible
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if bent, the mineral will NOT spring back to its original position after the stress is released
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Hardness
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-Mohs Scale
10. Diamond 5. Apatite
9. Corundum 4. Fluorite
8. Topaz 3. Calcite
7. Quartz 2. Gypsum
6. Orthoclase 1. Talc
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Cleavage
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-Tendency to break along the planes if weakness.
-Certain minerals break along distinct planes producing unique angles
-Not all minerals have this!!
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Fracture
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When minerals without cleavage, they _____
-Minerals lacking cleavage possess equally strong chemical bonds in all directions within the crystalline structure.
-Most minerals (without cleavage) produce an irregular ____ surfaces.
-Quartz break into what is known as a conchoidal ______.
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Density/Specific gravity
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___ of a mineral is usually measured in g/cm3 (D=m/v)
-___ is the ratio of mineral's weight to an equal volume of water (unitless)
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Reaction to acid
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Any carbonate material will fizz when in contact with hydrochloric acid.
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Magnetism
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-To identify between polymorphs of iron sulfide (FeS2), a magnet can be used.
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Taste
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-White minerals ; quartz or halite?
--LICK IT (salty taste)
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Chatoyancy
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-A silky appearance
-Produced in minerals with fibers or fibrous inclusions.
-The streak of light is always perpendicular to the direction of fibers.
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-A silky appearance
-Produced in minerals with fibers or fibrous inclusions.
-The streak of light is always perpendicular to the direction of fibers.
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Caused when light is split into 2 beams when entering a crystal with unique optical properties
-Result: 2 images
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Mineral classes
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-Based upon their anions (last portion of their chemical formula)
-Classes: silicates, halides, oxides, hydroxides, carbonates, etc.
-Nearly 4,000 have been "named"
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Mineral Species
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-Category of minerals with similar crystalline structures and chemical compositions.
-EX: the feldspar minerals -- potassium feldspar, plagioclase feldspar (Ca - Na range)
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Mineral varieties
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-Within species, minerals can be divided into _______
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Colors
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-Incorporation of trace elements results in different _____.
(quartz)
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-Only 8 minerals compose most minerals.
-98% of continental crust is these 8 minerals
-oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium
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The 8 most common elements in the Earth's crust
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-The most abundant mineral class, silicates.
-they account for more than 90% of earth's crust
-More than 800 species are known
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Silicon and oxygen combine to form::
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Building blocks of silicates
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Silicates are divided up into dark and light groups
-Determined by color and iron content
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Feldspar
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Light silicate
-Most common mineral group
-50% of earths crust is composed of this
-Multiple species exist
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Quartz
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Light silicate
-2nd most common mineral group
-Only mineral groups composed of purely Si + O
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Muscovite
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-Light silicate
-Light, clear mica
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Clay minerals
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-Light silicate
-Mostly soil, very small grains
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Olivine
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Dark silicate
-black to olive-green silicate
-Constitutes ~50% of the upper mantle
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Pryoxene
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Dark silicate
-Dark colored igneous minerals
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Hornblende
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Dark silicate
-dark green to black
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Biotite
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Dark silicate
-Dark, iron-rich mica
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Garnet
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Dark silicate
-Mostly dark red
-Mostly found in metamorphic rocks.
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92% of Earth's crust is made up of silicates
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Why is it important to know about silicates?
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Non-silicates and all other mineral classes are far less abundant than silicates
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What are non-silicates?
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Igneous rock
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Rock solidified from molten rock
-Magma or lava
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Magma
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below the earth's surface
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Lava
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underneath the earth's surface
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3 components to magma
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-Generated at various depths by melting of earth's crust and/or mantle
-upon melting, the magma body becomes less dense than surrounding rock (results in magma rising to the surface)
-Either completely or partly molten rock
-when cooled, forms an igneous rock composed of silicate miner…
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Liquid component
(Magma)
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-Known as melt, silicate melt, and silceous magma
-98% of hte melt is made up of the main 8
-varies in composition (based on silica content)
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high viscosity
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slow flow
(Magma)
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Low viscosity
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fast flow
(Magma)
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the igneous rock type that will form, as well as eruption type
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Composition and viscosity determine...
(Igneous rocks)
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Composition and viscosity determine...
(Igneous rocks)
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Pressure and viscosity have an inverse relationship
(TorF)
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Solid component
(Magma)
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-(If any) composed of silicate minerals already crystallized from the melt.
-found at the bottom of the magma body.
-crystal size and total amount increase as magma cools.
-during last stages of cooling, magma is a "crystalline much"
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at the bottom of the magma body
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Where does the solid component of magma end up?
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Gaseous component
(Magma)
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known as volatiles
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Volatile
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Materials that vaporize (form a gas) at earth's surface pressures.
-Most common in magma:
-Water vapor
-Carbon dioxide
-Sulfur dioxide
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-Beneath the surface, volatiles are incorporated into the melt portion of the magma.
-As pressures decrease, volatiles seperate from the magma
-as gases build up, they can actually propel magma to the surface
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How is it possible for volatiles to exist without magma?
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-If mamga solidifies before it erupts, colatiles will seperate from the original magma body and pool as hot water-rich fluids.
-They stay in the liquid phase due to high pressures.
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If magma never erupts, what happens to the volatiles?
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When molten rock cools, movement of hte main 8 begin to slow down.
-eventually enough to where chemical bonding occurs
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when can chemical bonding begin to occur (in a magma body)?
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-Beneath the Earth's surface from magma
-On the earth's surface from lava
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What are the two settings in which igneous rocks can form?
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Intrusive igneous rocks
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-Form beneath the Earth's surface
-AKA plutonic rocks
-Coarse - grained = visible mineral crystals
-Completely surrounded by country rock at the time of formation
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Country rock
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Rock native to a certain area
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Extrusive igneous rocks
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-Form beneath the Earth's surface from magma
-AKA volcanic rocks
-fire - grained = mineral crystals not visible to the naked eye
- less common than intrusive
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-Ultramafic
-Mafic
-Intermediate
-Felsic
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4 compostions of magma
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4 compostions of magma
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<45% silica
-very rarely reaches earth's surface
-high Mg content - high Fe content
-Earths; mantle is composed of this
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Mafic magma
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-45 - 52% silica = fluid flow
-MAGnesium
-FE - iron
-erupt between 1100-1250 dgC (solid @ 1000dgC)
-Dark silicates
-oceanic crust
-basalt
-Low viscosity
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Intermediate Magma
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53 - 65% silica
-"Gray area"
-less than 25% dark silicates
-formed in continental margins
-produce dangerous volcanoes
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Felsic Magma
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>65% silica = "thick"
-FELdpsar
-erupt at 700 dgC
-light silicates
-continental crust
-Granite
-"sticky" magma
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Texture
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Overall appearance based on the size, shape, and arrangement of mineral grains.
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the environment the rock is formed in
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From the texture you can determine...
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Little (microscopic) crystals
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Fast cooling = ???
(Crystal size)
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Fast cooling = ???
(Crystal size)
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Slow cooling = ???
(crystal size)
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Zero crystals (Volcanic gas)
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Extremely fast cooling = ???
(crystal size)
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Aphanitic
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Fine - grained
- Result of rapid solidification
-Need a microscope to see individual mineral grains
-color is used to determine composition
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Vesicular
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Many extrusive rocks have these spherical voids
-holes left by gas bubbles
-these rocks usually form in the upper zone of the lava flow
-quick cooling preserves
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Glassy
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Lava is thrown in the air and solidifies immediately
-Atoms re frozen before they are able to bond into a crystalline form
- volcanic gas = noncrystalline
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Phaneritic
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Mineral crystals are visible and identifiable
-Masses of intergrown equigranular crystals
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Equigranular
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Same size crystals/grains
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Pegmatitic
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under special circumstances, pegmatites may form.
-Mineral crystals are >1cm in diameter
-Pegmatites from late in the magma crytallization
- Consist of abnormally large crystals
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Porphyritic
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Coarse + fine
-crystals are known as phenocrysts
-first crystal to form when the magma is cooled slowly
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Pyroclastic
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Fragmental texture
-formed from consolidation of VRF's
-very fine ash, molten blobs, or large blocks
-common rock: welded tuff
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Tuff
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VRFs cemented together after cooling and falling back to earth
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Welded tuff
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VRFs fused together because they were still hot when impacting Earth.
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Partial melting
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Only SOME things will melt, but not ALL
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Plutons
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All plutonic rock bodies, no matter their shape or size, are called ____.
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Tabular
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Pluton classification
-Ressembles a tabletop
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Massive
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-Pluton classification
-Have no real shape at all
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Concordant
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Pluton classification
-form parallel to pre-existing features.
-Sill
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Discordant
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Pluton classification
-Cuts across pre-existing rock features
-Dike - Batholith
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Pluton classification
-Cuts across pre-existing rock features
-Dike - Batholith
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Discordant bodies
-Frequently used as conduits for magma to reach the surface
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Sill
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Cordant bodies that are nearly horizontal
-form as magma fins weakness in country rock, usually along sedimentary bedding planes
-can act as a storage unit for magma
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Batholith
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Discordant bodies
-Largest type of plutons
-Almost always felsic in composition
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Stocks
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Smaller massive bodies that are exposed
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Smaller massive bodies that are exposed
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It is believed that rising magma is able to make room for itself in the lower, more ductile region of the crust.
-Rock is more pliable...
-Known as "shouldering"
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Stoping
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The magma has to break the overlying rock to continue rising.
-Broken blocks sink through the magma body and pile up on its floor.
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GLY 101:Final Exam