Geology

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Convergent Plate Boundaries

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one plate subducts beneath other. subducting plate is always onceanic lithosphere because it is denser. strong compressive forces usually for mountain belts.
-part of subducting zone melts that becomes volcanoes
-creates deep trenches

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Transform Plate Boundaries

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PLATES SLIDE PAST ONE ANOTHER ON THE HORIZONTAL PLANE
-no new lithosphere is created
-no lithosphere is consume
-creates fracture zones

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3 Movement Mechanisms
RIDGE PUSH

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-gravitational force "pushing newly formed oceanic lithosphere form high elevation to lower elevation
-rocks at higher elevation because they are warmer and therefore less dense
-accounts for majority of movement

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3 Movement Mechanisms
SLAB PULL

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gravitational force pulls cold, dense lithospheric plate down

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3 Movement Mechanisms
CONVECTION

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-the flow of asthenosphere
-can + or - to other two processes

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Minerals

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-built up to become rocks
---rocks can be composed of many different minerals
---rocks need at least 1 type of mineral
-vary in size
-homogeneous, naturally occuring, inorganic, solid, chemical composition and crystalline structure
---class is not a mineral because there was no time for a crystalline structure to form
-made from chemical elements (form of matter you can't further break down)

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8 common elements by mass makes up over 98% of earth's crust

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Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium

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Silicate Minerals

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-most common type
-all have silicon (Si) and Oxygen in them
-tetrahedron shape
-a lot of the o atoms are shaved by Si atoms

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Quartz

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Silicate mineral
-has a unique property: pizoelectric

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Feldspar

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Silicate Mineral
-Most common mineral in Earth's crust
-differenciate by cation: K, Na, and Ca
a) potassium and plagioclase feldspar

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Micas

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Silicate Mineral
-crystallized into thin sheets
-muscorite, bictite, and chlorite
-clay minerals are all micas

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Amphiboles and Pyrocenes

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Silicate Mineral
-black to dark green
-contain Fe and Mg

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Oxides

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Have metal eations with oxygen anions

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Examples of Oxides

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-hematite (Fe2O3)
-magnetite (Fe3O4)
---most common mineral that preserves the earth's magnetic field because it is magnetic
-Ilmenite (FeTiO3)
-Cassiterite (Sn02)
-Carundum (Al2O3)
---very hard mineral that is used for grinding
---makes sapphire & rubies

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Sulfide Minerals

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-Have one or more metal bonded with sulfur
-many valuable metals are sulfides
-many have nice metallic luster

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Sulfate Minerals

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-all contain sulfate (SO4)2 group

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Carbonate Minerals

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-all contain carbonate (CO3)2 group
-most common mineral is calcite

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Phosphate Minerals

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all have phosphate (PO4)3 group

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Native Elements

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minerals made up of only one element

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Rock Classification
Igneous Rocks

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-all formed from molten rock
-can form on surface from lava as volcanic eruptions (extrusion)
-can form underground form magma (intrusion)
-minerals grow together

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Sedimentary Rocks

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-only form on Earth's surface
-made from sediments (broken up pieces of older rock, shells, skeletons, remains; precipitated from water)
-minerals cemented together by other minerals that are precipitated out

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Metamorphic Rocks

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-all form from older rocks
-rocks are altered by temperature and pressure
-rocks do not melt (that would make them igneous rocks)
-minerals align to create a foliation

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Lithification

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the process of cementary sediments to create a rock

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Tsunamis

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-long, broad waves in open ocean, fast moving
-short, tall waves in shallow areas from slowing down of the front of the wave and water piling up behind

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Igneous Rocks

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form from molten rock (magma/lava)
magma/lava composed of:
--liquid (molten rock)- individual ions and ionic complexes floating around
--solids- crystals of newly formed minerals, inclusions/xenoliths: fragments of older rock
---gas- volatides (dissolved gases). H2), CO2, SO2, H2S. usually escape at surface, which makes lava composition different from magma composition

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Magma Formation

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-rocks at earth's surface melt at ~900 degrees celcius to >1200 degrees
-geothermal gradient
-heat comes from: conduction from Earth's core to surface left over from earth's formation, or radioactive decay where heat is always release when isotopes radioactively decay

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geothermal gradient

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the change in temperature with depth

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(Increasing pressure raises the melting temperature of rocks)
Decompression Melting

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-lowering P usually lowers the melting point of rocks
process that melts rocks
-when rocks quickly rise up (decrease in P, T stays same), the rock melts
-occurs along mid-ocean ridges and hot spots and rifts

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(Increasing pressure raises the melting temperature of rocks)
Adding Volatiles

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-volatiles lower melting points
-volatiles get into these rocks at subduction zones
-most subduction zones have volcanoes associated with them

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(Increasing pressure raises the melting temperature of rocks)
Heat Transfer

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-really hot magma melts surrounding rocks if magma is higher than the melting point of the surrounding rocks

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Igneous Rock Classification

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-grain size and shape (texture)
-chemical composition
-phaneritic texture
---slowly cooling magma that produces large coarse minerals
---occurs underground (intrusive)
-aphanitic texture
---magma cools quickly producing tiny grains
---occurs at surgace (extrusive)
-composition of igneous rocks say something about the plate tectonics, formation environment, melting/freezing point, etc.

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Pyroclastic Materials

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Stuff erupted from volcanoes, fragments of rock
-ash: fine dust to sand size
-lapilli: pea to plum sized
-blocks and bombs: apple to refridgerator

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Tuff

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Pyroclastic material cemented together

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Silica

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controls a rock's viscosity (a measure of how easily/poorly something
-water: less viscous
-maple syrup: more viscous
-more silica= more viscosity, more viscosity=more explosiveness
-silica controls melting/freezing point

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Magma Evolution

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different minerals melting/freezing at different temperatures
---Bowen's Reaction Series (mineral crystallization sequence)
-different minerals have different densities

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Dikes

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-relatively thin sheets
-principle pathway to bring magma up from depth
-fills cracks in earth and pushes rocks apart horizontally

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Igneous Rocks at convergent plate boundaries

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magma created from the release of voltatiles from the subducting place
---mafic and very hot
---pods at bottom of the crust, which melts some crust, making felsic- intermediate composition

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Intrusive

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deep, large magma chambers

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Intrusive

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any body of magma that solidifies far beneath the earth's surface
-stocks: relatively small, area <100km2
-batholiths: relatively large plutons, area >100km2
-all consist of coarse-grained igneous rocks
-make up cores of mountain belts

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Sheeting Joints

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cracks that develop in rocks as pressure/weight is removed form overlaying rock
-function of brittle rock

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Why Barre Granite is so valuable

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-homogeneous
-fine-grained=easier for sculpting
-few imperfections
-human taste
-silicosis: lung disease caused by breathing in silica dust

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Pagmatites

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-small "pockets" within granite intrusions where the individual minerals grow to very large sizes
-last areas of magma to crystallize
-volatiles promote large crystal growth
--because there is high concentrations of volatiles
-often mined because they contain rare elements (sometimes)
-rare in VT granites

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Core of Volcano

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a vertical pipe that moves magma from below to lava on the surface

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crater

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where lava/pyroclastic materials erupt from

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amount of cement

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determines how strong a tuff is

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volcanic eruptions

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-vary depending on the type of volcano
-different types of volcanoes characterize different plate techtonic environments
---because composition varies with tectonic environments
-during eruption, volatiles get pushed out which pushes the magma up and out

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voilence of eruptions determined by

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-how much gas is dissolved in magma (more gas=more explosion)
-how easily volatiles can escape
---the more difficult it is to escape=the more explosive
---the more viscous = more explosive
---the more silica = greater amount of energy to break bonds= more viscous = more explosive

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Types of Volcanoes

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depend on
-type of igneous rock
-proportion of lava flow to pyroclastic material

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Cinder Cone Volcanoes

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-smallest
-only made from pyroclastic material
0usually erodes quickly because of loose material
-permanently extinct after 1 eruption
-may have a lava low that breeches the side of the cone

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Angle of Repose

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angle from the horizontal that is the steepest slope sediments can withstand before slumping

(angle often 30 degrees)

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seamounts

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"islands" that are not high enough to stick out above the water. formed from the extrusion of lava through central vent onto the sea floor

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basalt

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the volcanic rock that was extruded to for all of the islands
-a black, fine-grained igneous rock dominated by mafic minerals and plagioclase feldspar

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shield volcanoes

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molton basalt lava, very fluid and runny, when erupted from a central vent, forms gently-sloped volcanoes

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Hawaii Hot Spot

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the principal mountain on the island is an active volcano. all others on the island/seamount chain are innactive

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Hot Spots

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origin deep in the mantle and generate plumes of molten rock that rise upwards, through the asthenosphere and into the lithosphere. where this molton reaches the surface... a volcano forms

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Opal

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not a mineral because it does not possess a crystalline structure

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physical properties used to identify minerals

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color, luster, hardness, cleavage, & streak, density, solubility

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Single Element minerals

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-silver
-diamond
-copper
-gold
-graphite

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3 most common evaporite minerals

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halite, sylvite, and gypsum

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hardness of a mineral

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defined as the ability of a mineral to resist scratching and is more measure of the strength of the chemical bonds holding the mineral together

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Friedrich Mohs

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produced scale of mineral hardness in early 1800s.
-other common items can be used to test minerals- fingernail, penny, etc.

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cleavage plane

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individual minerals preferentially break parallel to planes of weakness in their internal atomic structure. the mineral breaks or cleaves along the weak chemical bonds holding the sheet of strongly bonded carbon atoms together.
-how the rock breaks apart

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basal cleavage

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cleavage in one direction allows minerals to form thin sheets, like a stack of paper

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prismatic cleavage

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cleavage in two directions often allowing the mineral to break into elongate "prisms"

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cubic cleavage

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three cleavages at 90 degrees to one another allow minerals to break into cubes

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rhombohedral cleavage

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three cleavages at angles other than 90 degrees produce rhombohedral faces and allow minerals to break into rhombohedrons

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octahedral cleavage

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cleavage in four directions that produce 8-sided double 4-sided pyramid shapes when minerals are broken

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luster

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the way a mineral reflects or transmits light to the observer
-metallic
-non metallic

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streak

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when powdered (ground with another stone, the residue color)

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gem minerals

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-weighed in units called carats
-carat, color, clarity, cut: determine price of diamond

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Japan

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-magnitude 9 earthquake
-off of northeastern coast
-result of thrust faulting along or near the convergent plate boundary where the Pacific Plate subducts beneath Japan

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thrust fault

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-the geometry of a subducting plate where one place is "thrusting" up and over another plate
-commonly occurs in mountain belts, albeit on a smaller scale

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tsunami (what happened in japan)

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the wave is flat, unlike wind-driven waves. as a tsunami wave approaches shallow water, it slows down and the rear of the wave catches up with the front, increasing the height of the wave

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ffoliation

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minerals in most metamorphic rocks are aligned producing a new layering (foliation)
-the parallel alignment of the minerals result from the pressure they were subjected to when they formed

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mafic/ultramfic

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dark-colored rocks with relatively little silica
-melts at temperatures in excess of 1000 celcius.
-resulting magma is much hotter
-when the mafic magma moves moves to an area with felsic, the felsic will melt and form magma
-way more dense than felsic

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felisic/intermediate

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light colored with higher percentages of silica
-melt at much lower temps (750-900)

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pjaneritic Texture

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slowly cooling magma producing large, easily visible to the eye, mineral grains

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Plutonic/intrusive igneous rock

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-igneous rocks with large grains have cooled slowly beneath the earths surface

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Aphanitic Texture

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quickly cooling magma (or lava) producing small, too small to see without a microscope, mineral grains

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extrusive igneous rocks

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small mineral grains that have cooled quickly, usually at or close to earth's surface

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what causes rocks to melt and produce magma

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-removal of volatiles (water or carbon dioxide) from rock
-increasing pressure, temp stays constant

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porphyritic granite

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large crystals of feldspar

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Dunite

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an ultramafic rock composed entirely of the mineral olivine (the rock in this picture).

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Peridotite and Dunite

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both form in the lower part of oceanic lithosphere (upper mantle): It’s the part of the asthenosphere that doesn’t melt.

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Peridotite

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an ultramafic rock composed of the minerals olivine + pyroxene.

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Euhedral

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crystals are those that are well-formed with sharp, easily-recognised faces. Normally, crystals do not form smooth faces or sharp crystal outlines. Many crystals grow from cooling liquid magma. As magma cools, the crystals grow and eventually touch each other, preventing crystal faces from forming properly or at all.

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vescular texture

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air bubbles formed from gas pushing out of earth's surface when magma is formed

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columnar joints

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forms in lava flows, sills, dikes, tuffs, and more
-more are straight with parallel sides
-some columns are curved and vary in width

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xenolith

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pieces of old rock floating in magma

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ions

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atoms that have lost or gained electrons

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decompression melting

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process that produces magma at divergent plate boundaries

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hydrothermal fluids

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sulfuric acid, mudpots, sulfur crystals

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calderas

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form when land collapses in the area. sketch can show how body of water existed, mountain range on top then collapse over it. causing eruption potential. then a volcano erupted in the area shown above.