final Flashcards
streams & different zones
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 *
what was 4.8 earthquake in NJ from?
fault system in NJ from the formation of Pangea => reopened during the Mesozoic and still has rocks slipping
why has the # of flood related deaths gone up? what are people usually doing when they die in a flood?
because people love living near the water; driving
how are watersheds created?
tophography separates drainage basins
what is the nesting for w&m watershed
w&m => college creek => james river => chesapeake bay => atlantic
how is streamflow measured?
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
ephemeral streams
streams that arise when it rains in dry climates, when the water table rises
why is vegetation important for streamflow?
vegetation reduces streamflow (ET)
types of water erosion processes
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
why are college creek and the grand canyon so diff?
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
what does abrasion favor?
sandstone, low vegetation, loose sand
competence
amount of sediment a stream can move
controls: (discharge, slope) longitudinal gradient
how do streams evolve?
- young streams are relatively straight and erode down to base level
- after concave up equilibrium, stream cuts side to side creating a flood plain
- stream flattens out the rugged landscape
- over time, base level can change so cycle starts over
concave up equilibrium
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
what happens when a stream is dammed?
sediment is blocked, sediment fills in upstream of dam, increased erosion downstream of damn
slot canyons
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
what happens water-wise during a flood?
water in the stream becomes higher than what the stream can handle
what is glacial maximum
30% of land covered in ice, last max was 20k years ago
how is sea level measured
hourly satelite measurements of local sea levels and average over 19 years
wburg sea level is 30m, during max it was 200m
types of ocean shore currents
- 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
why is ocean salty?
rivers carry products of chemical weathering, then water evaporates (500x more salty than rivers)
thermohaline circulation
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
controls on sea level
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
contributions to rising sea level
45% mountain glaciers (lots of surface area)
38% thermal expansion
13% melting of antartic ice sheet
4% ice loss from greenland
why does groundwater exist?
porosity => well sorted (same size) grains incr porosity
97% of unfrozen freshwater is groundwater
when is porosity created?
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
aquifers
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
why would clay, shale, and slate make SHIT aquifers
fine grains are parallel, in “plates”, so pores are not connected vertically => low permeability
how did the Ogallala Aquifer form?
- erosion of rocky mnts laid down sand & gravel
- rocky mnts covered in ice, ice melted way long time ago and flowed east
- ice grew & melted & grew & melted = 1,000 ft deep of saturated sediment
* 30% of nation’s irrigated groundwater
how do climate oscillations affect aquifers
glaciers grow and melt in cycles, supplying water to aquifers
how is dryness measured?
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
how & where do desserts form
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
types of deserts
- subtropics: (30deg N = sahara) (30deg S = kalahari, great sandy, patagonian)
- cold ocean currents: atacama
- rain-shadow: mojave
- polar: canada, siberia
- inland: gobi
where is driest place on earth and why?
atacama desert in south america, cold ocean currents from antarctica so little rain
why did desertification happen to dodge city, kansas
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)
climate oscillations
el nino: warm water away from cali, southwest states wet
la nina: warm water near cali, southwest states dry
dustbowl review
- 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
why are plants important during drought
- cool the surface (evapo-transportation)
- put moisture back into atmosphere
*tree rings are thinner during drought and cold
theres farming in kansas today, how?
AQUIFERS R GOAT, irrigation
glacial minimum vs maximum
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
CO2 now vs in mesozoic
now 420ppm vs meso 1000ppm
evidence for ice age (for the last maximum)
- 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
how are plankton evidence for the ice age?
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)
what causes ice age vs hot house?
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)
why no ice in mesozoic?
pangea centered around equator, no land near poles and hella CO2
glacier
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)
glacial moraine
lateral deposit of till (sediment in & deposited by glacier)
types:
- terminal
- lateral
- medial (when 2 laterals join)
glacial erosion types
abrasion, plucking
landforms
- 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
why is all ice melting bad
- sea level rising
- ocean circulation fucked up
- albedo gawn, oceans less capped and ocean warms up
how is temp changing now vs then?
recorded temp change in glaciers is 11C/15,000years = 0.0007C per year
now is 1.2C/140years = 0.008C per year
why did CO2 go way up after 1950s?
post WW2 expansion
in 1940-1980, CO2 went up but not global temp, why?
CO2 went up as pollution did, but atmospheric particles also went up, in 80s legislation passed to clean air (just particles tho, not CO2)
carbon sinks & why dont’t they help now?
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
how can land use increase albedo?
deforestation provides more flat surfaces for snow to lay
loess
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
how can we use ice to track atmosphere?
ice cores track little pockets of old air, track CO2, dust (as glaicals advance, mroe dust)
Younger Dryas period
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
sunspots
magnetic storms that slow convection on the sun, more sunspots more heat (abundance of them is cyclical)
