Earth Science Exam #2 (11/4/24) Flashcards
(71 cards)
1
Q
Annals of the Former World by John McPhee
A
- spent time going on road trips with geologists and he would drive around I-80 (NJ, across country)
- lots of rocks
2
Q
rocks: grafton, ny
A
- grafton gray wacky
- basis for roads all over upstate NY
- hard, won’t compact when cars go over it
3
Q
grand canyon
A
- carved out by the colorado river
- colorado plateau formed when the continent was squeezed and land got pushed up
- way to look at the past through rock formations
4
Q
pre-depositional environment: what is being deposited
A
sediment:
- material deposited on the earth’s surface by water, ice or air often by gravitation transport
- grains of sediment accumulate in a variety of settings (depositional enviro)
- recording things at lower elevations, gravity moves sediments downhill and deposits it
- record is inherently biased, uplifted material is not necessarily preserved because its being eroded and moved downhill
5
Q
where do sediments come from
A
rocks
6
Q
igneous rocks
A
- formed from the cooling of molten/lava material (crystallization)
- classified according to chemical composition and grain size (mode of origin)
7
Q
chemical composition of igneous rocks
A
- Felsic: Si- or AI-rich = light = low-density ex. granite continental crust
- Mafic: Mg- or Fe-rich = heavy = high density ex. Basalt oceanic crust
8
Q
sedimentary rocks
A
- physical (like ice-breaking rocks) and chemical weathering (erosion) break down of rocks
9
Q
three kinds of sedimentary rocks: detrital
A
- break up of preexisting rocks
- erosion transports material, re-deposited and cementation (lithification) occurs (often silica or calcite)
10
Q
three kinds of sedimentary rocks: biogenic
A
- fragments of skeletons of once-living organisms
11
Q
three kinds of sedimentary rocks: chemical
A
- precipitated from water solutions
- often lumped with biogenic due to the challenge of determining origin
12
Q
examples of biogenic/chemical sedimentary rocks
A
- evaporites: form in arid regions where sea water evaporates and leaves behind dissolved material that may or may not be biogenic in origin (halite, chert aka flint)
- limestones aka carbonate rocks
- precipitation from sea water
- accumulation of skeletal debris
13
Q
metamorphosis rocks
A
- alteration of other rocks via high pressures and temps
- alters both mineral composition and texture of original rock: igneous, sedimentary or metamorphic
- assigned grade based on level of heat/pressure exposure: high, medium, low grade
14
Q
types of metamorphic rocks
A
- regional: mountain chain
- contact: magma + rocks
- hydrothermal: hot fluids and rocks
- shock: extraterrestrial impact
- fault zone: plate boundaries
- burial: piles of debris
15
Q
rules of sediment deposition: actualism
A
- the fundamental physical and chemic principles that humans observe operating today have operated throughout Earth’s history
- physical relationships that we know about don’t change over time
- allowed us to think about the distant past and future and also places outside of Earth - the physics of the universe
16
Q
rules of sediment deposition: uniformitarianism
A
- “the present is the key to the past”
- if we find a rock, how does that rock form a long time ago, the best way to figure that out is where is that rock forming rn
- true with some exceptions:
- some events are unique to Earth’s past, the physics is the same
- sometimes things happen fast like catastrophes
- evolution: organisms change over time
17
Q
steno’s principles: superposition
A
in an undisturbed layer of rock, the oldest rocks lie at the bottom
18
Q
steno’s principles: original horizontality
A
all layers of rock are horizontal when they form
19
Q
original lateral continutiy
A
rock layers thin laterally to zero thickness, but can be cut by erosion
20
Q
depositional environments: climate
A
- determined by the atmosphere and ocean circulation
- the position of the continents and elevation
- dictates habitats and biomes
- which all together produced varied depositional environments
21
Q
where rocks can be deposited
A
- continental environments
- transitional environments (btw continental and marine)
- marine environments
22
Q
depositional environments: coal swamps
A
- coal: sedimentary, fossil flue, carbon, organic matter
- hot and wet climates with fern trees
- as vegetation fell it accumulated and buried organic matter which no longer interacts with oxygen (burial pressure)
- forming an anaerobic environment (transformed it into coal)
-coal deposits today: Illinois which means the climate at one point was extremely diff from now
23
Q
depositional environments: deltas
A
- coarse material is dropped off closest to shore and as it goes into open body of water the finer material gets dropped off
- pulses of stand sitting on top of silkstone: occur when a particular channel is activated, when bulk of water is coming down 1 channel
- eventually will switch to diff channel
- see different rock types and delt switching preserved in rock
24
Q
depositional environments: carbonate platforms
A
- where limestone is formed
- tropical waters
- enough dissolved calcium carbonate in the water that it creates bank (Bahama Banks)
- similar to coal reefs that form around volcanoes in the ocean
25
relative dating
- process of determining if one rock or geological event is older than another, without knowing their specific ages
- rock layers: oldest at the bottom, younger at the top
- fossil successions: trace organisms across diff sections of the earth, useful to form correlations between diff rock sequences in diff locactions
- magnetic stratigraphy: N and S pole on Earth change over time
26
absolute dating
- use of radioactive decay of elements to estimate the numerical age of material
- use known decay rates as geological clocks: decay happens at a constant rate over time
- volcanic eruption: magma or lava that solidifies and cools to form minerals
-look at the amount of parent material in the rock and amount of daughter material and calculate the diff to find age
- most elements occur in igneous rocks: time elapsed since crystallization
27
ages of the earth
currently cenozoic
mesozoic: triassic, jurassic
paleozoic: cambrian etc
precambrian: archean, proterozoic
28
abraham ortelius (1596)
- wrote the Americas were "torn away" from europe and africa by earthquakes and floods
as people started making better maps of the world they realized that the continents looked like puzzle pieces
29
Wegner's evidence: origin of continents and oceans 1915
- using the puzzle piece theory of the sahpe of the continents
- also indicated that lots of the other continents might fit as well
- Pangaea
- process of fitting continents together: continental drift
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Wegner's evidence: rock types
- types that occur on diff continents
- same layers of rock located in diff places
- noted that on each continent there are relatively similar rock types at similar periods of time
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Wegner's evidence: fossil record
- plant material that was fossilized and found in places where the continents would have been touching
- also animal fossils found in South Africa and in Brazil
32
Wegner's evidence: glacial deposits
- striations: little lines in the rocks moving in the same direction
- can look at the striations that used to make up Pangaea , all are radiating outwards of what used to be the center of the continent
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Wegner's evidence
- also included mountain ranges
- presented this evidence but people said he had no justification for what actually moved the continents
34
inside the earth
listen to lecture
35
marie tharp
- mapped the ocean floor
- during the cold war period so even though we knew things about the topography of the ocean floor it was not published
36
mapping the ocean floor
- found that the ocean includes mid-oceanic ridges
- identified a little valley at the summit of the ridges because of the detail and spacial resolution of the mapping
- iceland has a surface expression of a mid-ocean ridge, most are found in deep ocean
- ridge is result of upwelling hot material in the mantel
- one oceanic plate is moving left the other is going right: sea floor spreading
- as plates move apart magma is released inot the trough
- the magma meets with the ocean and cools to form new ocean crust
37
testing sea floor hypothesis
- use idea of magnetic pole reversals to test whether new formed crust would track those changes through time
- orientation is towards the magnetic north pole and it will stay there throughout existence, as layers appear they face diff directions
- also most earthquake activity occurs at edges of oceanic crust
38
Wegner's accumulated evidence
Shape of continents
Rock types
Fossils
Glacial deposits
Mountain chains
Mid-ocean ridges
Seafloor ages away from ridges
Seafloor magnetic polarity reversals
39
harry hess
- spend time mapping pacific ocean floor using sonar
- deepest part of the Pacific is very close to continental margin of Japan - Mariana's Trench 11km
- hypothesized that renches are were ocean floor was destoryed and recycled
- crust is created at ocean ridges, moves in 2 directions from that crust, convection in mantel drives the crust away from the mid ocena ridge and when it runs into another plate, one will dive below it and form a trench
40
theory of plate tectonics
Mid-ocean ridges result of convection in the mantel
Ware, high ridge, spreads, cools, increases in density, eventually sinks
Movements driven by convection, ridge push and slab pull
Gravity of high ridge adds to the motion of the convection cell pulling higher material lower into the ocean
Slab is being pulled into the earth because its heavy
Ridge push and slab pull interacting with the convective cells of the mantel driving plate tectonics
In the mantel, there is basalt, dense igneous rock compared to the felsic material that makes up the continents
As the basalt spreads away from the ridge it cools and gets denser and denser
41
continental drift
Low velocity zone is evidence of partial melt in the upper mantle - not solid, actually more plastic
Upper mantle flows over geological time
Plates sit atop this viscous mantle
Continental plates sit higher than oceanic due to density differences
Atlantic ocean is slowly getting bigger because it is spreading along the mid-ocean ridge
North American plate is moving west and interacting with the Pacific plate, results in lots of earthquake activity on the west coast of the US
Mid-ocean ridge in the Pacific and Indian Oceans
42
plate margins: divergent
- Africa, where continent is being ripped apart
- two plates moving in opposite directions
43
plate margins: convergent
- two plates are running into each other
- ocean crust runs into continental
- OC is denser than C
- OC subsides under C
- Pacific plate is subducting under NA plate, creating Olympic Mountains and Cascades
- also creates volcanic mountains such as Saint Helens
- OC runs into OC
- as OC ages it gets denser
- older crust subducted under younger rust
- Isalnds streching from Alaska to Russia
- melting resutls in lots of volcanoes
- C runs into C
- like when India ran into Eurasian plate
- neither are high density so they don't dive quickly into earth
- creates mountain ranges like Himalayas
44
plate tectonics: transform
- plates are moving side by side
- San Andreas fault
45
plate tectonics + rock cycle
listen to this again
46
major geochemical cycles: nitrogen
- nox pollution
- lightening fixates nitrogen in the atmosphere
- essential nutrients to create plant matter and animals eat that creating cycle
47
major geochemical cycles: phosphorus
- mining operations dig up phosphorus and they spread it on fields as a fertilizer, gets washed off into bodies of water creating lots of algae
48
major geochemical cycles: oxygen
no notes
49
major geochemical cycles: carbon
- unable to answer why carbon dioxide is going up without understanding carbon cycle
- time scales really matter
50
chemical carbon resevoirs
- places where elements are sequestered for a period of time
- period of time is diff for each of the reservoirs
- can grow or shrink over time
- dependent on the rate at which the material flows in and out of the reservoir
51
carbon cycle facts
- allows life to live on earth
- planet would ice over if the cycle was disrupted, also could get really hot if there is runaway greenhouse gas effect
- times in earth's history where the planet was much colder and warmer than today, but still within habitable range
- roughly 65 million years ago was Cretaceous period, lots of gases in atmosphere and planet was warmest it has been (since then CO2 had been on a decline until humans came along)
52
carbon characteristics
- up to 4 bonds per atom
- bonds it creates are relatively strong
- releases lots of energy when they are broken
- creates human DNA
53
fast carbon cycle
- movement of carbon through life forms/the biosphere
- plants, phytoplankton
- plants might use stored sugar and use the energy, animals eat the plants and respire, fire can consume it, decay of material through microbes
- can see fast cycle when we track amount of CO2 in the atmosphere
- max CO2 through the red peaks of 3d plot to show diff time variables and seasonal cycles
54
fast carbon cycle: photosynthesis
CO2 + H2O + energy (sun) = CH2O (sugar) + O2
55
fast carbon cycle: respiration
- CH2O + O2 (oxidizing) = CO2 + H2O + energy
- can happen in the gut of an animal
- microbes in the soil
- wildfire
56
fast carbon cycle: degradation pathway, methanogenesis
- 2CH2O → CO2 + CH4
- anoxic sub-surface environments, places without a lot of oxygen
- happens quickly year over year, tied in with season cycle
57
atmospheric CO2
- steady state: when input equals outputs
- 60 gton in flow through respiration and decomposition → 60 gton outflow of photosynthesis
- residence time: average amount of time a substance spends in a reservoir before its removed
- RT = amount in reservoir/ inflow OR outflow rate
58
fast organic carbon cycle diagram
refer to slide
59
fast carbon cycle: surface ocean
- primary producers: phytoplankton
- diatom makes shell out of quartz, within diatom there is organic matter that photosynthesizes and creates sugar
- coccolithophore makes shell out of calcium carbonate and the plates fall to the ocean floor to create chalk
- radiolarian and foraminifera eat diatom and cocco
- forminifera: helps recreate climate on earth at diff periods of time
- create larger fecal matter
60
fast carbon cycle: biological pump
- SFC = photosynthesis
- deep ocean = respiration
- fecal matter, fecal rain - zooplankton
- heavier and denser so they settle and bring organic matter into the deep ocean and begin to decompose
- nutrients come back to SFC through upwelling
61
depth profile of chemical species in the ocean: oxygen
- highest concentration at the surface because the waste product of photosynthesis is oxygen which needs light (photic zone)
- as you go deeper there is less oxygen creation by plankton
- creatures start to sink and oxygen respires and combines with the organic carbon and a lot of the oxygen gets used up
62
depth profile of chemical species in the ocean: nitrate
- low at surface bc organisms at surface eat it
increases in intermediate zone bc (finish lecture)
63
depth profile of chemical species in the ocean: CO2
- low at the surface bc its becoming part of the organisms
- organisms are perspired creating more CO2 in the deep ocean
64
slow carbon cycle
- after organic carbon is sent to deep ocean
- a tiny fraction of which is lithified as sedimentary rocks
- takes a long time to turn over
65
slow carbon cycle: chemical weathering
- things that get stuck in rocks needs to go back to the atmosphere (CO2)
- highlights the importance of plate tectonics bc that is how we get sedimentary rocks at bottom of ocean back into atmosphere
- reservoir long time (listen again)
66
slow carbon cycle types of carbon
- organic carbon in sedimentary rocks ~1C
- fossil fuels
- coal and oil
- high concentration of organic C unlike sedimentary rocks
- inorganic carbon
- carbonate ions
- ocean bicarbonate ions
- limestone
67
marine carbon cycle
- exchange of CO2 at the earth's surface
- more CO2 in ATM than at the SFC, causes diffusion
- areas where ocean is taking in carbon have lots of photosynthesis and are cooler, areas releasing carbon are around equator, warmer and in upwelling areas
68
marine carbon cycle: reactions of inorganic carbon water
- H2O + CO2 ↔ H2CO3 (carbonic acid)
- pushed to the right, creating more H and bicarbonate ions
- H2CO3 (disossciates) ↔ H+ (hydrogen ion) + HCO3- (bicarbonate ion)
- additon of H is most important, pushed to the left to form more bicarbonate
- not a lot of carbonate ionsin the ocean, if we were to burn all fossil fuels we would run out of carbonate atoms
69
weathering: carbonates
- limestones
- weathering: CaCO3 + H2O + CO2 (carbonic acid)→ Ca2+ + 2HCO3- (bicarbonate)
- carbonate precipitation:
Ca2+ + 2HCO3- → CaCO3 + H2O + CO
70
weathering: silicates
- granite, basalt, clastic sedimentary rocks
- vast majority of rocks
- silicate weathering: CaSiO3 + 2H2O + 2 CO2 → Ca2+ + 2HCO3- + H2O + SiO2
- followed by carbonate precipitation (take silicate and make it into carbonate): Ca2+ + 2HCO3- → CaCO3 + H2O + CO2
- started with 2 CO2 ended up with only 1, means it is in the rock now
- rate of weathering are sensitive to temp
- form a neg feedback loop
- silicate weathering is earth's thermostat on geological time scale (listen again)
71
complete carbon cycle
- carbonate precipitation/rock formation in ocean
- sea floor spreading
- subduction
- melting of carbonate rock
- volcanism and tectonic uplift complete the cycle
