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73 Cards in this Set
- Front
- Back
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Aa Lava
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viscous, sharp lava
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pahoehoe lava
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fluid with swirly texture
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Cinder Cone Volcanoes
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• Finite lifespan
• Small magma chamber • Fountaining lava • Most are andesite or basalt • Pop up LIKE DAISIES • Piles of rocks - no lava flows to construct |
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tambora
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year without a summer, active strato volcano in indonesia
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toba
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decreased population, violent erruption in indonesia
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protolith
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preexisting parent rock
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formula for metamorphic rock
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Pressure plus temperature
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Regional Metamorphism
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increase in both temperature and pressure, widespread area, subduction zones
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Contact Metamorphism
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high temperature but no real change in pressure, caused by intrusion, zone of contact depends on intrusion but always smaller than regional
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Three Features of Metamorphic rocks
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1. Form in the solid state
2. A single protolith can become many different kinds of metamorphic rocks a. Depends on pressure and temperature 3. Strong deformation of the rock -> regional |
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Recrystallization
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causes reorientation and thus strong foliation as minerals follow preferred direction
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mineralogic changes
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metamorphism can cause neomorphism or metasomatism (minerals are gained or lost)
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Change in metamorphic rocks as P&T rise
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Slate, phyllite, schist, gneiss
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Oceanic subduction
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High pressure, low heat
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regional metamorphism
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high pressure, high heat
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contact metamorphism
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high heat, low pressure
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metamorphic facies
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groups of mineral compositions in metamorphic rocks that are typical for a certain pressure -temperature space (particular P&T conditions)
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When would homosapiens appear if the entire span of geologic time was condensed into a year?
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11:00 PM December 31st
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when was the cambrian esplosion?
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500 my
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when did the dinosaurs go extinct?
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65my
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Principle of superposition
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in a series of sedimentary rocks, the layers at the bottom are older than the layers on top
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Principle of original horizontality
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sedimentary layers are deposited horizontally
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Principle of lateral continuity
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sediment layers are deposited all the way across the basin - laterally continuous
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Principle of cross cutting relationships
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intrusions are younger than the layers they cut
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Principle of inclusions
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the rock containing the inclusions is younger than the inclusions themselves
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Unconformity
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erosion takes place and erases sedimentary history
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Angular unconformity
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layers get shifted into an angular position and erosion takes place - layer placed on top horizontally
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how long ago was the cenezoic era?
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65 mya
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how long ago was the mesozoic era?
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210 mya
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how long ago was the paleozoic era?
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542 mya
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what happened in between the Cenozoic and mesozoic eras?
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a mass extinction of 70% of life
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what occurred in between the mesozoic and the Paleozoic eras?
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a mass extinction of 90% of life
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what occurred in between the Paleozoic and Precambrian eras?
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the Cambrian explosion
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when did the precambrian era start?
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4,500 mya
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Arch Bishop Ussher
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1664
○ Used ages in the bible ○ 9 AM October 26,4004 BC |
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Lord Kelvin
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1897
○ Heated rock cools at a certain rate ○ 20-40 million years old Underestimated because he didn't know about radioactive decay |
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John Joy
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1899
○ Weathering of Feldspar makes ocean salty ○ How long would it take rivers to make oceans as salty as they are ○ 80-90 million ○ Animals remove calcium carbonate to make shells Ocean at an equilibrium |
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Radioactive Isotope
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Atom with atomic mass differing
Decays to form nonradioactive isotope+heat Decays at constant rate Each isotope has a certain rate (half life) |
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radioactive potassium
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K40 ->Ar40
1,300 my |
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Uranium 238
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U238 -> Pb206
4,500 my |
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Uranium 235
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U235 -> Pb 207
713 my |
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Rubidium
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Rb87 -> Sr87
48,800 my |
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Samarium
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Sm147 -> Nd 143
106,000 my |
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carbon
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C14 -> N14
5,730 years |
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What elements should you use to date things?
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faster half lives for young substances, slower half lives for older
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what is the approximate limit for measuring short half lives of old rocks?
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50,000 years
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what age do you get if you date a metamorphic rock?
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the age of the metamorphism, not the protolith
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what age do you get if you date a sedimentary rock?
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the age of the minerals, not depositoin
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What is the KT boundary?
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the boundary in between the cenozoic and paleozoic eras containing the cretaceous and tertiary ages where 70% of life went extinct
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walter alvarez
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developed asteroid extinction alongside Luis Alvarez
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what did Luis Alvarez suggest that his son do to date the clay deposit?
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measure meteor dust (iridium)
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what other evidence supported the Alvarez's theory?
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microtektite and shocked lamellae quartz
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what do sedimentary rocks tell us?
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what environments were like
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Clastic sedimentary rocks
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made from pieces of pre-existing rocks
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Biogenic Sedimentary rocks
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come from living things. Generated by biological processes
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what does the Composition of Clasts tell you?
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about the source area, composition
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what determines the size of clasts?
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the energy of the formation area (speed of flow)
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what are the clast sizes?
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boulder, cobble, pebble, granule, sand, silt, clay
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what is sorting?
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how much variety exists in grain sizes
well sorted vs. poorly sorted |
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what determines sorting?
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constancy of velocity of transportation
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what is rounding?
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how circular or angular grains are
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how is rounding determined?
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distance of travel
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how do clasts break?
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heat, trees, ice,
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lake depositional environment
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poorly sorted, angular, mix
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river depositional environment
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well sorted, more rounded, composition varies depending on contributors, smaller grain sizes
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Desert Lake depositional environment
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evaporites and an arid environment
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glacier depositional environment
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wide range of grain sizes, poorly sorted
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Beach depositional environment
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well sorted, mix of a lot of things, all kind of the same stuff, mostly quartz
started in mountains |
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organic depositional environment
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biogenic processes, limestone
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Carbonate platforms
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arbonate sediments create a platform of limestone
Produced by marine organisms usually by trenches |
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Atoll
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1. Stage 1 - Volcano rises
2. Stage 2. - Volcano becomes extinct and reef forms 3. Stage 3. - builds up 4. Stage4 - Reef covers |
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what's up with the Mediterranean sea?
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○ Hypothesis: Med. Sea was desert
§ Evaporites same age § Change in fossils § Nile river would have been waterfall □ "Notch" Present □ Nile Canyon |
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how long would it take for the Mediterranean sea to evaporate if the strait of Gibraltar was blocked?
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around 1,000 years
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