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Env Geo midterm
midterrrrrrm
Question | Answer |
---|---|
What are the "spheres"? | Hydro, Bio, Litho, Atmo |
What is the malthusian formula for population growth? | I = P * A * T |
What is the difference between linear and exponential growth? | -linear (add fixed quantity/unit time) -exponential (proportional, good for population, rate of growth proportional to # people) |
How do you get k (the growth constant?) | -k = 1/t ln(N/No) -t is the span of time -N is the highest value -No is the lowest value |
How do you get doubling time? | doubling time = 70/(k * 100) |
Vandermeer maint points | -intraspecific competition limits population growth to sustainable levels -carrying capacity must also be taken into account |
Vitoek Paper main points | -land change/habitat disruption is bad -of natural areas left, they don’t have buffer zones -land change results in atmospheric chemical changes “We are changing the earth more rapidly than we are understanding it” -Ag, biogeochemical, & ocean issues |
Resource needs/impacts of population growth: | -increased energy use -greater food and clean water requirements -more land and space needed -disruption of natural systems |
environmental systems | group of linked, interrelated and interacting objects/phenomena |
formula for measuring steady vs transient state | delta S = inputs - outputs |
Steady State | Input = output • managed system such as university with constant enrollment • stock constant • delta S = 0 |
Transient states | -input < output • use of fossil fuels • stock reduced • delta S negative -input > output • pollution of a lake with heavy metals • stock grows • delta S positive |
Residence time | (average time that something stays in the system, applies for steady state) • pool/flux |
Human Domination of Earth’s Ecosystems - Vitousek | -so 40% total • decreased biodiversity • habitat fragmentation • changing atmospheric chemical concentration • runoff and erosion • fire frequency • albedo (how reflective the earth’s surface is) |
CO2 - Vitousek | -280 ppmv pre 1800 (during interglacials) -400-280 = 120/280 = 42% effect by humans -messes with sediment transport (can’t get to beaches) |
Water - Vitousek | -dams and impoundments, only 2% of N.A. rivers unimpeded -6% of runoff evaporated -humans using 50% of available fresh water (70% of this is agriculture) |
Nitrogen - Vitousek | atmospheric = N2 NH3 = fixed N fixing bacteria use enzyme (nitrogenase) yearly, 90 mil metric tons of N fixed on land, = amount at sea we’ve 2x'ed that, 25m mt f fuels 40m m (alfalfa, legumes, etc) ^ NO2 (GG), eutrophication, algal blooms, acid r |
Haber process | industrial N fixation, using high temp & pressure to make fertilizer |
Foley paper topics | Food production, freshwater resources, forests, regional air/climate, infectious diseases, confronting effects |
“Global consequences of land use” Foley | -since 1850, 1/3 of CO2 comes from land use -“ecosystem goods and services” essential products (food, fiber, fresh water) and environmental processes (flood control, water purification) -Pasture is new biome 40%, runoff, barely any return for fert input |
Foley land use solutions | • coffee farms near forests (~1km) increase yield 20% more • NYC purchased catskill mtns for water filtration (saved 5-7 bil) |
Soils | • isotropic (same) → anisotropic (layered) • start to develop horizons • secondary minerals and organic matter |
Pedogenesis | soil formation |
Soil horizons | • O (organic) • A (mixed organic & mineral matter) • E (eluviation, leached layer) • B (zone of accumulation – clays, iron oxide, some organic matter) • C (chemically weathered parent material) • R (regolith, non chemically weathered rock/sediment) |
soil forming factors | • Climate (P=E?) • Parent material • Relief • Time • Organisms |
Mollisols | o P=E o Flat o Grasslands o Loess over limestone |
Pedology | soil in its natural position |
What causes erosion? | slope/area of land |
How does one quantify erosion? | -river budgets -sedimentary rock volumes (from Cambrian to now) -plot comparisons |
What is a drought defined by? | • persistence – lasting 10+ years (how long until there’s 2 years above average rainfall) • abruptness – significantly shorter than persistence • magnitude – 5% change from norm |
Dust Bowl Summary | NM, KS, CO, OK. Homestead act + WW1 (no more wheat from german-occupied russia) + more homestead = wheat $. Mollisols went airborne after grass roots dug up. Mechanized plowing. Drought. |
Flood | A flood is any relatively high streamflow that overtops the natural or artificial banks of a river. |
Discharge | Discharge is another term for streamflow; it is the measured volume of water that moves past a point in the river in a given amount of time. Discharge is usually expressed in cubic feet per second. |
Cubic foot per second | One cubic foot per second (cfs) is about 450 gallons per minute. |
Floodplain | The floodplain is the relatively flat lowland that borders a river, usually dry but subject to flooding. Floodplain soils actually are former flood deposits. |
Recurrence interval | The average number of years between floods of a certain size is the recurrence interval or return period. The actual number of years between floods of any given size varies a lot because of the naturally changing climate |
Hydrograph | A hydrograph is a graph that shows changes in discharge or river stage over time. The time scale may be in minutes, hours, days, months, years, or decades. |
River stage | The river stage is the height of the water in the river, measured relative to an arbitrary fixed point. |
How do you determine growth rate for a straight line? | Slope of line. (y2-y1/x2-x1) |
What is the k value/unit time? | a percentage, not a number |
How many people do floods kill annually? | a million |
River development | -initially, in young streams channels are relatively straight as the river cuts down to base level -after achieving a graded profile, stream will cut side to side, creating a flood plain -rivers can therefore flatten out a rugged landscape. |
What makes a flood worse? | • Permeability of the soil • Putting roads everywhere • Land use (construction/development/pavement) • Vegetation • Relief • Antecedent moisture (how wet are the soils to begin with?) • Artificial bottlenecks in the rivers (constrict flow) |
How do you find recurrence interval? | RI = (# of years on record + 1)/magnitude rank |
Watershed budget data | -as streamflow goes up, other things go up • Dissolved exports (Ca, Na, N) • solid exports (sediment, sand, twigs) -clear cutting doesn’t do anything really with erosion • 1.7 m/My is typical • (ag is 600 m/My) • clear cutting is more like 3m/My |
Hubbard Brook relevant info | -discharge went up 30-40% -suspended sediment export went up a factor of 5-6ish -dissolved load export went up by a lot |