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101 Cards in this Set
- Front
- Back
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oceans of the world
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largest to smallest: paciffic, atlantic, indian, artic
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ocean as a basin
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highest to lowest: continental shelf, continental slope, continental rise, basin
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ocean floor topography
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highly variable with ridges, trenches, seamounts, etc.
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ocean as briny water
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around 97% of ocean water is sodium, the rest is dissolved salts (sodium, chloride, sulfate, etc.)
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salinity
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grams of salt per grams of ocean water 0.035, 3.5%, 35 0/00
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importance of salinity
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plays a role in ocean currents and cilmate change
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ocean water properties
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distinct vertical structure with sharp variations below the surface
properties of surface waters very different from deep waters cline: region between surface water and deep water surface waters: less than 1 km deep -- warmer, saltier, less dense than deep waters |
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ocean temp. behavior
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deep water is similar temp. at all latitudes
warmest water near the equator near poles deep water temps. extend towards the surface north south asymmetry |
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ocean salinity behavior
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tropics are saltiest
near equator and tropics surface water is saltier atlantic is saltier than paciffic -- not effect on mediterranean southern most pacific and northern most atlantic have similar salinities |
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causes of variation in salinity
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enhanced by evaporation of ocean waters and glacier and ice formation
reduced my greater amts. of fresh water -- precipitation and river runoff surface salinity higher near tropics due to higher evaporation -- lower at high lattitudes due to less evaporiation net flow of water from tropics to mid-latitudes -- this leaves salt behind |
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ocean circulation
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movement requires force -- uneven heating and pressure gradient force: sun heats earth surface, air the comes in contact gets hot and less dense, less dense air rises, this creates low pressure, surrounding air converges
BUT.. ocean is heated on the top, not bottom. makes surface water less dense than lower water -- result is stable stratification atmospheric winds give rise to horizontal surface circulation variations in salinity cause vertical exchange between surface waters and deep waters |
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tsunami vs. mega- tsunami
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occurs when underwater earthquake causes an upthrust max. wave height 30 m
mega: caused by landslides -- max height 500 m to 1 km |
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two components of ocean circulation
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1. wind-driven circulation: surface layer
2. thermohaline circulation: circulation of deep ocean and exchange of waters between surface and deep ocean |
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surface circulation
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arises from atmospheric winds pushing on surface waters
modified by corioliss effect and cont. boundaries caused by large scale gyres -- circular courses of motion complicated due to friction and rotation |
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directions of gyres
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clockwise in northern hemisphere
counterclockwise is southern hemisphere |
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tub toys in pacific subartic gyre
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cargo of kids bath toys fell over in the north pacific
toys were tracked 4,000 km to SE alaska features of this: western and eastern boundary currents -- western current localized and intense, eastern more disperse stimulation of rising waters from deep ocean along eastern bounds of gyres |
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regions of upwelling
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1. on eastern bounds of gyres
2. along coasts where winds push waters away from the shore -- coastal upwelling |
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thermohaline circulation
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downwelling and the deep ocean
upwelling waters must be replaced with downwelling waters from the surface this means that there mustbe a deep ocean circulation to connect regions of upwelling and downwelling driven by density differences caused by salinity and temp. |
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ocean water density
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enhanced by lower temps. and higher salinity
glass of water and salt experiment |
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T-S diagram
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qaunt. relationship between density, temp. and salinity
even if surface water is warmer than deep water, it can be denser and start to sink if evap. or freezing increases salinity |
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the way circulation occurs today
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evaporation of water as it moves north on gulf stream causes sinking towards greenland
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north atlantic deep water (NADW)
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formed by sinking surface water near greenland that flows south causing conveyer belt circulation
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ocean conveyer belt circulation
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water is exchanged from all oceans at all depths
currently warm water flows north along atlantic east coast to iceland warm water exchanges heat with cooler air, becoming cooler and saltier -- this causes water to become denser and sink flowing south along floor of atlantic continues to flow on floor around floor of africa and upwells in the north pacific surface water in N. pacific makes room for upwelled water by moving south passing asia and australia and catching beginning of gulf stream in central america across atlantic |
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climate and earth's energy budget
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result of ocean circ. = flow of heat from tropics to high latitudes
ice core data suggests that ocean can switch from mode to another in just a decade -- shifts in and out of ice ages |
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ice age intensities
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mild ice age: circ. only sinks south of iceland -- no sinking north of iceland; reduces amt. of water circulated in conveyor belt; causes cooling in northern latitudes
coldest ice-age mode: surface water does not sink in atlantic and little or none is circulated in conveyor |
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influx of fresh water in north atlantic
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when conveyer is in a stable warm state, amt. of freshwater inflow to atlantic can change without causing any severe changes in conveyor
ocean circ. is strong and large amts. and heat is transferred north, warming europe as freshwater flow increases, there isn't much change until a certain threshold had been crossed causing circulation to decreases and cooling europe by 2-5 deg. C large drop in freshwater inflow is needed for normal state to return evidence: last major glaciation, younger dryas |
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younger dryas southern cooling
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about 13,000 yrs. ago going from ice age to present intergalcial period
about 10,000 yrs. ago climate randomly changed ad in a decade the climate switched to ice-age randomly for 1000 yrs. cold temps. in north hemisphere accompaned by warm temps. in south hemisphere bipolar seesaw could have been caused by melting of glaciers possibly due to melting glaciers |
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phytoplankton
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bottom of ocean foodchain
float freely in ocean green plants -- carry out photosynthesis need sunlight to survive and photosynthesize but sunlight sunlight reaches depths of about 100 m |
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zooplankton
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do not carry out photosynthesis
eat phytoplankton |
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photosynthesis
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green plants use sunlight to make organic material water and CO2 in a process to make oxygen
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respiration and decay
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reverse of photosyntesis
organic material + O2 --> CO2+ H2O + ? |
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closed chemical cycle
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combo. of photosynthesis and respiration/decay
no chemical is consumed or generated |
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photic zone
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layer of ocean with enough sunlight to allow photosynthesis
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survival of phytoplankton
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problem is that they are denser than water and sink out of photic zone where they die and decompose
require more than just sunlight, they also need nutrients |
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problems with phytoplankton
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amt. of photosynth. w/ phytoplankton occurs is limited by amt. of nutrients in photic zone
photosnyth. depletes amt. of nutrients in this area sinking and decay of phytoplankton cause more nutrients in the deep ocean -- where they cant by used by phytoplankton |
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biological pump
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ocean nutrient cycle
causes greater transport of organic carbon and nutrients from surface to deep ocean important because it takes around 500 years for nutrients and C this keeps nutrients in surface in short supply and limits productivity |
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ocean regions with highest productivity
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high latitudes: surface is very thin or nonexistent; upwelling regions; near river deltas
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"puzzles" about the ocean
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1. slow leakage of nutrients and sediments -- why don't we run out?
2. evidence that the oceans on earth about 3.7 billion yrs. ago -- fossils est. life started 500-660 million yrs. ago -- but math evidence suggests that ocean is no more than 140 million yrs. old |
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major zones of the earth
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crust
mantle core |
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mineral
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natural inorganic element or compound with a definite internal arrangement of ions a fixed chemical comp. or one within natural limits
contain 8/92 main elements -- mainly elements that make up the crust oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium oxygen is most abundant and appears with other elements as oxides divided into 10 categories -- silicates most abundant -- some minerals formed by ionic substitution |
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rocks
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aggregates of one or more minerals
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changes in minerals
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have limited chemical composition
if elements in that crystal change, it becomes a different mineral minor flexbility in chemical makeup due to ionic substitution if mineral is crystalizing out a liquid that it rich in 2 elements the crystal may incorporate substitute ions instead of the more appropriate ions. |
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plagioclase series
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minerals that range in chemical composition
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mineral identification
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1. hardness
2. color/luster/streak 3. density 4. cleavage/fracture -- how mineral splits 5. magnetic properties etc... |
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silicate
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basic building block: SILICA TETRAHEDRON- each silicon atom is attached to 4 oxygen atoms by tetrahedral bods -- results in a 4 charge on the silicate group
major rock-forming minerals OLIVINES AND GARNET PYROXENES: single chains of tetrahedra balanced by similar metal cations and sodiums AMPHIBOLES: double chains of tetrahedra balanced by similar cations MICAS AND CLAY MINERALS FELDSPARS QUARTZ |
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mineral formation
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formed through crystalization
high temps. and pressures within earth cause rocks to melt forming magma as it cools, various elements and ions come together for form solds with spec. structures -- ex. crystal different minerals form at different temps. |
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rock formation
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type is determined by the processes that lead to formation or rocks and the minerals they are made up of
minerals within a given rock will tend crystalize at similar temps. 3 types: igneous, sedimentary, metamorphic |
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types of minerals that make up rocks
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feldspars, quartz, micas, pyroxenes, amphiboles, clays -- all silicates
calcite and dolmite -- carbonates SILICATES = ROCK FORMER CLASS |
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igneous
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formed from magma crystalization
-- extrusive: volcanic; rapid cooling; derived from upper mantle; rich in iron and magnesium >> mafic (basalts - olivine, pyroxine, plagioclase) -- inrustive: plutonic; slow cooling; derived from crust; rich in silicates ad aluminum >> sialic (granites - feldspar, quartz, mica) |
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sedimentary
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formed by sedimentation and compaction of material and compaction of material -- litification
usually forms in layers (detirital - shale, sandstone; biological - limestone, chert; evaporites: gypsum, anhydrite, halite, calcite) |
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metamorphic
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rock that has been chemically altered while in the solid stae from exposure to high temps. and pressures
-- recrystalization (slate, marbl, gneiss) |
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rock cycle
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SEE SLIDES
sediments -- sed. rock -- metamorphic rock -- magma -- intrusive/extrusive igneous -- weathering |
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meteorites
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leftover material from formation of rocky planets
represent material from existing planet or disintegrated one may represent analogues to comp. of earth WAY TO INFER PROPERTIES ABOUT THE INNER EARTH |
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types of meteorites
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stony meteories
- chondrites: most common type; as old as our solar system - achondrites: formed by melting and recrystalization on or w/in parent bodies; give us good info. about igneous properties within this body stony iron meteorites: least common - pallasites - mesosiderites iron meteorites: mostly iron nichol alloys |
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seismograph
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remote sensing instrument
records small tremors in the earth consists of moving paper or recording drum mounted to bedrock with suspended weight and pen above when bedrock shakes and moves the weight still remains vertical -- result is a plot of bedrock motion seismogram = plot of motion |
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what is determined from siesmograms
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location of earthquakes and other disturbances
intensity of earthquake basic properties of underlying material of the solid earth |
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waves within the earth
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waves propagate outward like waves on a lake
2 types: -- surface waves: travel along surface -- body waves: travel through interior -- type we focus on |
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types of body waves
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P-waves (primary waves): compression waves/sound waves
S-waves (secondary/shear waves): displacement perpendicular to wave direction P-waves are faster than S-waves |
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finding epicenter of disturbance
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can be determined by triangulation using 3+ seismographs
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what scientists have learned from siesmographs
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outer core is molten -- S-Shadow: s-waves only propegate through inner core since it is a solid
changes of properties of the earth's interior/density cause waves to bend -- from observations of arrival times of waves to different locations, these properties are inferred |
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lithosphere
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first 10-125 km of solid earth -- consists of oceanic and cont. crust material plus uppermost portion of the mantle -- rigid, acts a single unit
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asthensphere
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about 100 km in depth -- low p-wave velocities due to layer being plastic (not liquid, but not rigid - close to melting pt.); provides material that is ejected from volcanoes; accounts for reboud of crust after ice ages; malleable layer on which plates can flow
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sumatra-andaman earthquake
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strongest since advent of seismology
caused tsunami released as much energy as earthquakes from 1976-1990 along indonesian subduction zone |
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plate tectonics
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theory of solid earth that clears up puzzles of earth's history previously discussed
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Alfred Wegner
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came up with plate tectonics
also came up with continental drift was a meterologist |
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Wegner's cont. drift theory
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based on similarities of fossils from N. america and europe
present day continents were once part of 1 continent called pangea -- about 200-300 million yrs. ago it split ad pieces have been moving apart ever since |
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evidence of continental drift theory
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1. cost fit of african and s. american coastlines (fit best when using cont. shelf edges)
2. glacial features from same time periods appear in s. america, africa, india, and australia -- best explained if continents were once connected (striations matched up) 3. fossils of same plants and animals found on all continents (previously explained by land bridges) 4. large scale geological features on diff. continents matched (ex: appilacians) 5. fossils found in some places do not match current climates (glossopteris fossils) |
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construction of pangea
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glacial from till and striations: polar areas
sand dunes: deserts coral reefs: tropics different dist. from today means poles either wandered or continents drifted |
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problems of continental drift theory
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dismissed by most scientists
no viable mechanism for drifting continents were not deformed by ocean crust good evidence -- not inconclusive |
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continental drift reborn tectonics
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convectino currents -- which bring hot magma up from deep mantle and cool rock rock back down -- could drive cont. motion
mid-ocean ridges: chain of sub sea volcanic mts. along the center of the ocean basins -- active seismic belts |
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theory of sea-floor spreading
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ocean floor is young
ocean floor age has certain pattern with youngest floor near central ridges support comes from magnetic polarity of basalt material on seafloor: fresh sea floor magnetized due to earth's magnetic polarity at the time of formation -- striped pattern on ocean floor magma comes up at ocean floor ridges -- erupts as sub-sea volcanoes and product new basalt crust this crust spreads causing ocean floor to move away from central ridges when crust reaches continent it plunges below because continental material (granite) is less dense that oceanic material (basalt) new mtns. formed along boundaries |
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oceanic vs. continental crust
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oceanic: composed of basalt; more dense
continental: composed of granite; less dense continental crust floats above oceanic; thickest underneath high mtn. ranges and thinnest at lowlands granite crust rises as continents erode |
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isostatic equililbrium
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allows lithosphere to be suppoted by asthenoshere (ex.: mtns. are less dense than mantle material but sink into mante until they displace a mass equal to the mtn. mass)
some areas are not equilibrium because mass has recently and abrubtly changed |
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plate tectonic theory vs. continental drift
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continents don't plow through oceanic crust; they actually are part of plates that move on plastic asthenosphere
convection currents are the driving force |
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theory vs. hypothesis vs. law
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theory: group of prop. used as principles to explain something
hypothesis: conjecture proposed as an explanation for some occurance law: well-est. prop. that are regarded as fact |
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types of plate motion
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divergent
convergent transform |
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divergent plate boundaries
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lithospheric plates that move away from each other; as plates move apart, new cust is produced
exampeles from ocean: smokers, deep sea hot springs not all divergent boundaries are in the ocean -- iceland |
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convergent plate boundaries
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surface area of the earth is finite SO... b/c new crust is always created, convergent boundaries are where old crust is consumed
this is a result of subduction along convergent boundaries |
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subduction
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helps to close the rock cycle
earthquakes are generated at rigid plate as it is subducted into the mantle magma along to top of sinking slabs rises to surface to form stratovolanoes -- accounts for dist. of earthquakes and mtn. ranges along coastlines |
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3 types of convergent plate boundaries
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1. ocean-continent convergent plate boundary
2. ocean-ocean plate convergence 3. continent-continent convergent plate boundaries |
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ocean-continent convergent plate boundary
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: oceanic lith. plate is pushed toward and beneath continental plate since ocean plate is denser -- subduction produces magma -- causes volcanoes and mtn. formation
ring of fire in pacific delineates many ocean-continent plate boundaries -- trenches (subduction zones) and mtn. ranges (formed from stratovolcanoes) |
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ocean-ocean plate convergence
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once plate is subducted under another forming a trench
volcanic activity produced by partial metling of descending plate or overlying lith. causes a pile of lava on ocean floor that will rise above sea level and form and island volcano these form in arcs and tend to be parallel to trenches |
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continent-continent convergent plate boundaries
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when 2 continents meet neither is subducted; crust buckles and is pushed up or to the side
forms mtns. |
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transform plate boundary
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plates slide past eachother
ex: san andreas fault |
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energy of plate tectonics
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plate move about 4 cm/yr.
energy comes from interior of earth -- geothermal energy (~.1W/m^2) small compared to solar, but still a lot source: radioactive decay, residual heat from earth formation |
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radioactive decay
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spont. decomp. of unstable isotopes of potassium, uranium, and thorium w/in earth ; when these decay they give off energy
all radioactive elements are decreasing not permanent energy source |
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volcanoes
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eruption brings magma to surface to form ext. igneous rock
classification: -- eruptive history: active, dormant, extinct -- topographic form: shield, strato, cinder, basalt |
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shield volcano
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round with low profile
formed from sucessive magma flows basaltic composition -- fluid when melted not steep or explosive ex: Hawaii usually form over hot spots -- not always convergent |
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startovolcanoes
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built from successive layers of lava of andestic comp.
intermediate of basalt and granatic ext. rock wide base, high peak solid debris -- pyroclastic material andesitic material not fluid so more explosive ex: mt. st. helen |
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cinder cones
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small and pyroclastic
deep depressions that are larger than initial crater mini stratovolcanos |
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basaltic volcanoes
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flood plane of basaltic rock
occur due to giant plutons -- when intrusive rock is formed from magma -- hard rock with sed. on top which washes away to reveal this |
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mtn. ranges
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occurs along convergent boundaries -- orogeny
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islands
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shield volcanoes found on ocean-ocean convergent plates
they produce island arcs islands always form on continent side of boudary |
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hotspots
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at certain places in asthenosphere a fountain of hot lava is cont. flowing towards the surface
lava is lighter than surrounding rock so it erupts and produces a seamount which eventually turned into an island volcano as plate above hotspot moves, it cuts of magma and volcano dies once one volcano dies a new one develops over the next hot spot this produces trail of volcanic islands and seamounts erosion causes older islands to become smaller many occur at triple junctions -- 3 plates coming together |
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how continents are formed
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stable interior of ancient rock -- craton
formed from early island arcs that collide and form granatic cont. nuclei craton not covered by sed. dep. know as shield terranes: nuclei that are added to crustal welding to other peices of crust oregen: belt of deformation along the welding |
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plates today
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euasian
phillipine juan de fuca n. american carribean s. american nazca cocos pacific australian-indian antartica african arabian |
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movement of plates today
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based on plate boundaries and knowledge of rifts, motion of lith. over hotspots we can deduce direction and speed of movement
arrows rep. rel. motion sum of all must equal 0 otherwise earth would get bigger or smaller |
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microplates
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prominent along US coast
smaller plates |
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dance of the contients
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continents coming together to form super-cont. pangea
continents breaking apart new cont. material forming |
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the wilson cycle
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continents move at about 4 cm per year
circ of earth 2piR is about 40,000 km continents initially in contact with each other move away in opposite directions at same speed given speed of 40 km per million yrs. this woul take 500 million yrs. Pw = piR/v could slow down as amt. of radioactive material depletes each would travel at 20,000 km |
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importance of rock cycle
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without it life on earth would die
tectonics help recycle nutrients needed to maintain life CO2 would not be recycled and would end up as carbonate sediments -- photosynthesis in ocean and on surface would stop |
