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94 Cards in this Set
- Front
- Back
Uniformitarianism
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the physical, chemical and biological laws that operate today also operated in the past
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law of superposition
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the youngest layer of rock is on top and the oldest is on the bottom
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relative dating
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events are placed in their proper sequence
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layers of the earth by composition
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core: iron rich and nickel rich with minor oxygen, silicon and sulfur
mantle: most of earth's volume, the dominant rock is peridotite crust: divided into oceanic and continental, mostly made up of basalt |
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divergent boundary
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plates move away from eachother
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convergent boundary
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plates move into eachother
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transform fault boundaries
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plates slide past eachother
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layers of the earth by physical properties(8)
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lithosphere and asthenosphere: crust and upper mantle
mesosphere: lower mantle outer core: liquid layers of flowing iron inner core: behaves like a solid because of pressure hydrosphere: dynamic mass of water atmosphere: gaseous envelope around the earth biosphere: all life on earth geosphere: lies beneath atmosphere and oceans |
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rock cycle (6)
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1. magma migrates to the earth's surface and cools
2. igneous rock formed by crystallized magma 3. weathering and transportation 4. particles deposited as sediment 5. sediment is cemented and compacted by heavy weight 6. pressure and heat change the rock into metamorphic, if subjected to more heat and pressure, it goes back into magma |
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what is a mineral
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it is the building block of rocks and is an inorganic solid that possesses an orderly internal structure and a definite chemical composition
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what are the 5 mineral characterisitics
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1. must occur naturally
2. must be solid at surface temperature and pressure 3. must have a definite chemical composition 4. usually inorganic |
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polymorph
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minerals that join together in more than 1 possible arrangement. ex. coal and diamond
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what is an igneous rock
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formed by the cooling and solidification of magma
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magma
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a silicate melt which may contain early formed crystals or inclusions/xenoliths
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intrusive
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plutonic or under ground
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extrusive
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volcanic or above ground
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factors affecting magma viscosity
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silica content: higher silica means more viscous
volatiles: higher volatiles means less visous |
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factors affecting crystal size
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rate of cooling: faster cooling means smaller crystals
viscosity: higher viscosity means bigger crystals |
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factors affecting cooling rate of magma
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location: intrusive means slower cooling
size of magma body: large means slower cooling |
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porphyritic texture
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crystals are not uniform in size, large crystals called phenocrysts form first and are then surrounded by smaller crystals called the matrix/groundmass
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equigranular texture
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cooling rate is constant, so the crystals are the same size
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glassy texture
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disordered and no crystals
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aphanitic texture
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small microscopic crystals
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phaneritic texture
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visible crystals
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pegmatitic crystals
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very large crystals, and high volatile content
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Name 6 textures occuring in volcanic rocks
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aphanitic, prophyritic, glassy, vesicular, pyroclastic, amygdular
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name 2 intrusive rock textures (plutonic)
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aphanitic, and porphyritic
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what are the four main igneous compositional groups
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felsic: light coloured silicates, part of the conitinental crust, usually intrusive
intermediate: 20-40% dark minerals from explosive volcanic activity mafic: dark silicates, oceanic crust and calcium rich feldspar ultra mafic: very rare almost 100% ferromagnesian and is a major part of the mantle |
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role of heat in making magma
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temperature increases with depth with the geothermal gradient between 20-30 degrees per km
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role of pressure in making magma
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increase in confining pressure increases a rock's melting temperature and when confining pressure drops, we get decompression melting
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role of volatiles in making magma
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volatiles cause rocks to melt at lower temperatures
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stratification
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a structure developed when fine grained pyroclastics like cinders, ashes and dust settle through water or air and are deposited in consecutive layers. this rock is termed tuff
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what is bowen's reaction series
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as magma cools, minerals crystallizw in a systematic fashion based on their melting points. the silica content becomes greater as crystallization proceeds
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proof supporting bowen's reaction (3)
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zoning in plagioclase, reaction rims in ferromagnesian minerals, and mineral associations and antipathies.
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list bowen's reaction series
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discontinuous: continuous:
olivine calcic plagioclase pyrocene amphibole biotite sodic plagioclase kspar muscovite quartz |
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explain how igenous rocks are diverse (3)
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1. magmatic differentiation: rocks of different composition form from the same magma by crystal settling, filter press action,
2. magmas of different composition 3. magma mixing: more buoyant magma overtakes magma that rises more slowly and the mixed magma will be different from the other two original magmas |
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magmatic stoping
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detaching and engulfing blocks of country rock. the engulfed rock may become assimilated, be an inclusion or be a xenolith
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volcanic neck/plug
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solidified lava in the throat of a volcano
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fissure flow
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fluid basaltic lava pouring out from fissures and are very rare and form vast sheets
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plutons
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an intrusive body of rock
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batholith
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largest of igneous intrusions. it is massive and discordant
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laccolith
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a massive intrusion bowing up the strata and concordant
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sill
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a thin extensive tabular and concordant intrusion with strata
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dike
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a tabular discordant intrusion to the strata
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stock
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a massive, discordant pluton similar to but smaller than a batholith
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pyroclastic flows
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nuee ardente. glowing avalanche. there is a cloud of incandescent gas that is released forming tuff and welded tuff. ex. mt. pelee
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lahar
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volcanic mud flow ex. nevado del ruiz
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what are the different types of lava flows (3)
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pahoehoe: formed by fluid lava. are smooth and ropy
aa: formed by thicker lava, has rough jagged blocks pillow lava: formed in oceans as lava cools under water |
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lava dome
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a viscous, silica rich lava that builds up in bulbous masses
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columnar jointing
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due to lava cooling and contracting. this causes cracks in the lava
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where are most active volcanoes found
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pacific rim of fire, mediterranean, african rift valley, and oceanic ridge belt
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fissure eruption
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ex. laki fissure in iceland, which covered a huge area. we do not usually see these eruptions
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central vent eruption and types of volcanoes
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1 central location of the eruption.
1. shield volcano: large gentle slopes, ex mauna loa 2. composite cone: medium, steep slopes near summit and gentle slopes at base. both pyroclastic and lava flows. ex. vesuvius 3. cinder cone: small steep slopes, often found in the caldera of large volcanoes, mostly pyroclastics. ex. sunset crater arizona |
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caldera eruptions
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very rare and extremely violent eruptions. different from calderas inside volcanoes. yellowstone is a resurgent caldera because its floor has slowly been rising and doming up since its last eruption. they leave us with volcanic activity like geysers and hot springs
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what are sedimentary rocks
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form at or near the earth's surface due to accumulation and consolidation of sediments
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what are clastic sediments
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composed of products of physical weathering
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stratification
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bedding or layering
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lithification
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transformation into solid rock
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name the wentworth size scale (4)
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-conglomerate: gravel size 2mm
-sandstone: sand size 1/16 mm -siltstone: silt size 1/256 mm claystone: clay size finer than 1/256 mm |
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how do we describe clastic sediments (6)
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-sorting: poorly or well sorted
-shape: equant, tabular or rod shaped -roundness: means no sharp edges -sphericity: means the particle is shaped like a sphere -angularity: how sharp the edges are -fissile or blocky |
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biochemical and chemical rocks
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natural precipitates of aqueous solutions deposited through organic life or evaporated oceans
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evaporites
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rock salt and gypsum: may form a play which is a land locked basing
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carbonates
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dominantly calcite form limestone.
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travertine/dripstone
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formed from calcite deposits in caves. stalactites grow on the ceiling and stalagmites grow on the gorund
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dolostone formation
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form with dolomite mineral. form from limestone by replacement from magnesium bearing waters
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ripple marks
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these occur on the surface of sand deposits when wind or water currents move sand size particles, forming ridges and troughs perpendicular to the current direction
we have current ripple marks and ossilation ripple marks |
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cross bedding
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sand grains are deposited at an inclination to the horizontal and will indicate the direction of current flow
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graded bed
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when a sediment laden current slows down and deposits particles coursest at the bottom and finest at the top due to a short lived turbidity current
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mudcracks
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when clay or mud dries out, it contracts and causes cracks to form
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diagenesis
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the physical, chemical, and biological processes that take place after sediment is deposited but before metamorphism occurs
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sedimentary facies
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sedimentary rocks characterized by chemical, physical or biological features that reflect a specific environment of deposition
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what is metamorphism
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a solid state transformation of pre existing rocks occuring well below the earth surface in response to heat, pressure and chemically active fluids.. there is a change in mineralogy, texture and structure
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heat and metamorphism
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about 100 to about 800 degrees. the geothermal gradient is about 25 degrees per km
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pressure and metamorphism
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about 1 k bar up to about 12 k bar. confining pressure increases with depth at about 250 bars per km. we also get directed pressure from things like plate tectonics with uneven direction
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fluids and metamorphism
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may be in pore spaces,, released by chemical reactions, in volatiles in magma, or migrating ions. fluids facilitate the growth of minerals because they increase the exchange of ions inducing chemical reactions. it is isochemical meaning that the net chemical composition of the rock does not change. h2o and co2 are usually present in metamorphic reactions
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classification of foliated metamorphic rocks (3)
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slaty: very fine foliations and parallel planes of splitting du to parallel minerals like mica and graphite
schistose: foliation in coursely grained rocks due to well developed parallelism of more than half of the minerals gneissic: rocks are coarsely foliated and is more widely spaced. bands may be uniform or wavy |
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classification of non foliated metamorphic rocks (2)
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granoblastic: a granular texture where recrystallization of minerals forms equidimensional crystals
hornfelsic: dense |
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types of metamorphism (2)
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contact: due to heat from plutons. depth is < 8km and causes a halo or aureole, new minerals may form, intensity decreases away from the plutons and rocks are massive and non foliated
regional metamorphism: affects a large area, due o both heat and pressure, occurs at depth, rocks are compressed and deformed, there is directed pressure and this causes foliation. there is gradation in intensity of metamorphism |
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index mineral
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characterizes a given intensity of metamorphism and has developed under a specific range of temperature and pressure conditions
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metamorphic zones
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an area of equal metamorphic intensity between isograds in which the mineral content in rocks remains constant
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isograd
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a line on a map connecting points of equal metamorphic intensity, usually indicated by the first appearance of a given index mineral
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metamorphic facies
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metamorphic rocks characterized by mineral assemblages that have formed within specific pressure-temperature conditions
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migmatite
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high-grade regional metamorphism. light coloured silicates will melt faster than dark ferromagnesians, so light bands of igenous rock will crosscut or parallel the foliation of the older darker rock. this is a mixed rock
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paired metamorphic belts
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in some regions, blueschist facies were found close to amphibolite or granulite facies rocks. these paired belts were difficult to explain until the advent of plate tectonic theory and the process of subduction.
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what is weathering
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an in situ change in rocks and minerals with little or no transport of particles occuring at or near the surface due to the atmosphere, water and living organisms
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physical weathering and its types
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Disintegration of rocks and minerals into smaller pieces
1. frost action, exfoliation(due to unloading), temperature changes, living organisms |
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chemical weathering, its types, and its products
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decomposition or transformation of rocks and minerals as they are chemically altered
1. types: solution, hydration, oxidation and hydrolysis 2. products of chemical weathering are salts in solution, iron oxide, silica in solution and clay minerals |
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factors influencing rates of weathering (6)
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-joints: more fractures = more surface area
-particle size: more surface area with wider particles -depth: more rapid weathering at surface -slope: weathered products move down slope -composition: minerals weather in the same order as in bowen's reaction series, quartz is quite resistant -climate: humid and tropical climates have rapid chemical weathering as well as climates with frost thaw cycles (frost action) |
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differential weatheirng
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variations in rate of weathering creating land forms
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regolith
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discontinuous cover of unconsolidated weathered rock debris overlying solid bed rock
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soil
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upper part of the regolith
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erosion
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a process where rock and mineral particles are picked up and transported from 1 place to another
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deposition (7 types)
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when an erosional agent can no longer transport sediment, deposits are formed
-fluvial: streams -marine: salt water -glacial: ice -Aeolian: wind lacustrine: lakes |
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spheroidal weathering
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chemical weather attacks the edges and corners first. as the outer layers of rounded blocks undergo chemical weathering, newly formed clay minerals take up more volume than previous minerals and the volume expansion causes cracks and the outer shells fall of creating boulders
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