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geology > final > Flashcards

final Flashcards

1
Q

streams & different zones

A

surface water moving in a channel, always wants to cut down or erode to sea level

unsaturated zone: above water table (pores are mix of air&water)
saturated zone: water table & below (pores are only water)

  • transports weathering products to ocean for rock cycle *
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2
Q

what was 4.8 earthquake in NJ from?

A

fault system in NJ from the formation of Pangea => reopened during the Mesozoic and still has rocks slipping

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3
Q

why has the # of flood related deaths gone up? what are people usually doing when they die in a flood?

A

because people love living near the water; driving

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4
Q

how are watersheds created?

A

tophography separates drainage basins

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5
Q

what is the nesting for w&m watershed

A

w&m => college creek => james river => chesapeake bay => atlantic

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6
Q

how is streamflow measured?

A

discharge aka Q is volume/time
Q = P - ET + ΔS
P - precipitation
ET - plant water use
ΔS - change in storage (ground water, lakes, ice)

*Q will have delayed, but exponential reaction to sudden precipitation

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7
Q

ephemeral streams

A

streams that arise when it rains in dry climates, when the water table rises

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8
Q

why is vegetation important for streamflow?

A

vegetation reduces streamflow (ET)

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9
Q

types of water erosion processes

A

scouring - water lifts loose sediment
break&lifting - flowing water tears off bedrock
abrasion - loose sand scrapes away at bedrock (when there are eddies in water, circular erosion cuts happen)
dissolution - water dissolves ionic bonds

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10
Q

why are college creek and the grand canyon so diff?

A

time, volume of water, vegetation, sea level
also, recent (~20mya) uplife of colorado plateau, so colorado river needed to cut down even more to get to sea level

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11
Q

what does abrasion favor?

A

sandstone, low vegetation, loose sand

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12
Q

competence

A

amount of sediment a stream can move

controls: (discharge, slope) longitudinal gradient

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13
Q

how do streams evolve?

A
  1. young streams are relatively straight and erode down to base level
  2. after concave up equilibrium, stream cuts side to side creating a flood plain
  3. stream flattens out the rugged landscape
  • over time, base level can change so cycle starts over
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14
Q

concave up equilibrium

A

the shape streams evolve to to balance competence with sediment supply;
- from the side, its a slope where as you go down, more tribuary streams join and Q increases, bottom is base level

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15
Q

what happens when a stream is dammed?

A

sediment is blocked, sediment fills in upstream of dam, increased erosion downstream of damn

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16
Q

slot canyons

A

stream channels that are so narrow you have to walk sideways, made from abrasion
- why none in VA?
=> lower elevation than in UT or AZ, more vegetation, less loose sand

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17
Q

what happens water-wise during a flood?

A

water in the stream becomes higher than what the stream can handle

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18
Q

what is glacial maximum

A

30% of land covered in ice, last max was 20k years ago

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19
Q

how is sea level measured

A

hourly satelite measurements of local sea levels and average over 19 years

wburg sea level is 30m, during max it was 200m

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20
Q

types of ocean shore currents

A
  • they drag sediment
    longshore = zigzag (approach at angle, fall back w gravity)
    rip = two opposite circles that pull you in but then back to shore
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21
Q

why is ocean salty?

A

rivers carry products of chemical weathering, then water evaporates (500x more salty than rivers)

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22
Q

thermohaline circulation

A

how: cold & salty sink
where:
surface current gets colder & saltier towards north, sinks to deep current near greenland, goes back up in indian ocean and pacific

*if current stops, north hemisphere gets colder, mini ice age maybe
* if greenland melts, influx of freshwater and current fucked

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23
Q

controls on sea level

A

ocean volume (rising everywhere):
- glacial & ice melt (biggest cause)
- thermal expansion of water
land:
- glacial rebound
- sediment compaction (ex: New Orleans)
- plate convergence (mountain building pushes land up)

*sea level rise is greater on East Coast

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24
Q

contributions to rising sea level

A

45% mountain glaciers (lots of surface area)
38% thermal expansion
13% melting of antartic ice sheet
4% ice loss from greenland

25
Q

why does groundwater exist?

A

porosity => well sorted (same size) grains incr porosity

97% of unfrozen freshwater is groundwater

26
Q

when is porosity created?

A

primary: during formation of rock
- ex [vessicular basalt, porosity formed from gas bubbles in lava]
- ex [clastic sedimentary rocks]
secondary: after rock forms
- ex:fractures, jointed rocks]

*most rocks have 1-30% porosity

27
Q

aquifers

A

body of geological material that stores big amounts of water (groundwater resource) ex: sand & gravel deposits
- material must have high porosity & permeability (how connected the pores are)
- ~12 in the USA

28
Q

why would clay, shale, and slate make SHIT aquifers

A

fine grains are parallel, in “plates”, so pores are not connected vertically => low permeability

29
Q

how did the Ogallala Aquifer form?

A
  1. erosion of rocky mnts laid down sand & gravel
  2. rocky mnts covered in ice, ice melted way long time ago and flowed east
  3. ice grew & melted & grew & melted = 1,000 ft deep of saturated sediment
    * 30% of nation’s irrigated groundwater
30
Q

how do climate oscillations affect aquifers

A

glaciers grow and melt in cycles, supplying water to aquifers

31
Q

how is dryness measured?

A

Aridity Index (AI) = Annual Precipitation (P) / Precipitation Evaporation Transportation (PET)
=> AI <0.5 is arid!
- willyburg: P=120, ET=80, AI=1.5
- las vegas: P=10, ET=200, AI=0.05

32
Q

how & where do desserts form

A

hadley cells (30deg N & 30deg S):
1. warm moist air rises near equator (low pressure)
2. spreads out away from it & precipitates
3. cool dry air descends 30deg away, as it descends into high pressure it warms

rain shadow (leeward side of mountain):
1. moist air rises over mountain
2. cools, condenses, precipitates windward side
3. dry air reaches the leeward side and descends, warming

33
Q

types of deserts

A
  • subtropics: (30deg N = sahara) (30deg S = kalahari, great sandy, patagonian)
  • cold ocean currents: atacama
  • rain-shadow: mojave
  • polar: canada, siberia
  • inland: gobi
34
Q

where is driest place on earth and why?

A

atacama desert in south america, cold ocean currents from antarctica so little rain

35
Q

why did desertification happen to dodge city, kansas

A

P = 550mm, ET = 1100,mm/yr, AI = 0.5 => ARID, so on the border of being a desert and precipitation pattern (10year wet/dry cycle) was heavily variable (the land usage was the final trigger)

36
Q

climate oscillations

A

el nino: warm water away from cali, southwest states wet
la nina: warm water near cali, southwest states dry

37
Q

dustbowl review

A
  • homestead act 1862 giving land if you farmed
  • prairie grass roots were long asf
  • climate had drought cycle
  • rainfall was 300-400mm (compared to normal 550) during 1875-1910
38
Q

why are plants important during drought

A
  • cool the surface (evapo-transportation)
  • put moisture back into atmosphere

*tree rings are thinner during drought and cold

39
Q

theres farming in kansas today, how?

A

AQUIFERS R GOAT, irrigation

40
Q

glacial minimum vs maximum

A

min is 10% of land covered in ice, happening now, last min 125,000 years ago
max is 30%, last max was 20,000 years ago

41
Q

CO2 now vs in mesozoic

A

now 420ppm vs meso 1000ppm

42
Q

evidence for ice age (for the last maximum)

A
  • glacial erratic (huge boulders)
  • glacial deposits (poorly sorted debris)
  • glacial erosion (U valleys, cirques)
  • abrasion marks in rocks
  • glacial rebound
  • evidenve of lower sea level 20k years ago
43
Q

how are plankton evidence for the ice age?

A

foraminifera - plankton w CaCO3 shells
during ice age:
- O16 in ice (clouds rain out heavy O18 before they get to land)
- plankton have O18 shells (O18 rained into ocean, lighter O16 all evaporated)

44
Q

what causes ice age vs hot house?

A

external forcings aka Malnkovic cycles (2-4deg change):
- 100ky earth’s orbit does from circle to oval (matches glacial cycle)
- earth’s tilt goes from 22 to 24 eveyr 41ky
- earth’s axis wobbles in a circle every 26k years

internal forcing:
- volcanism
- plate tectonics
- land distribution

internal feedback amplifiers:
- ice albedo
- dust
- greenhouse gases (global warming speeds decay, more gas, more warm)

45
Q

why no ice in mesozoic?

A

pangea centered around equator, no land near poles and hella CO2

46
Q

glacier

A

moving body of recrystallized (bc of snow packing) ice that lasts year round; flows b/c crystal slide past each other
types:
- ice sheets: start at poles
- mountain: start at high elevation (biggest to sea level rise)

47
Q

glacial moraine

A

lateral deposit of till (sediment in & deposited by glacier)
types:
- terminal
- lateral
- medial (when 2 laterals join)

48
Q

glacial erosion types

A

abrasion, plucking

49
Q

landforms

A
  • roche mountonee: bed rock thats abrased then plucked
  • drumlin: hill formed from moraine that glacier plowed over
  • esker: ridges of sand & gravel that were originally channels of meltwater at the base of glaciers
  • pluvial lakes: cold air near glaciers condensed & rained ex: salt lake in UT
  • cirque: circular erosion from glacier
  • arete: ridge in between two ^^
  • horn: point of 3 ^^ coming tgt
50
Q

why is all ice melting bad

A
  • sea level rising
  • ocean circulation fucked up
  • albedo gawn, oceans less capped and ocean warms up
51
Q

how is temp changing now vs then?

A

recorded temp change in glaciers is 11C/15,000years = 0.0007C per year
now is 1.2C/140years = 0.008C per year

52
Q

why did CO2 go way up after 1950s?

A

post WW2 expansion

53
Q

in 1940-1980, CO2 went up but not global temp, why?

A

CO2 went up as pollution did, but atmospheric particles also went up, in 80s legislation passed to clean air (just particles tho, not CO2)

54
Q

carbon sinks & why dont’t they help now?

A

natural places that remove/store excess CO2 ex: plants, oceans
they are already full of CO2/ our emission rate is higher then what they can take in

55
Q

how can land use increase albedo?

A

deforestation provides more flat surfaces for snow to lay

56
Q

loess

A

wind-blown silt, creates very fertile soils for agriculture ex: great plains, alaska, mississippi valley

hella loess blown during glacial max b/c glaciers create windy, dusty conditions

57
Q

how can we use ice to track atmosphere?

A

ice cores track little pockets of old air, track CO2, dust (as glaicals advance, mroe dust)

58
Q

Younger Dryas period

A

period of intense cooling after years of warming 11k years ago, shows that earth’s system is complex
- thought that ocean circulation was disrupted by melting ice

59
Q

sunspots

A

magnetic storms that slow convection on the sun, more sunspots more heat (abundance of them is cyclical)

geology (3 decks)

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