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- permanent bodies of ice that move down slope or outward under the stress of their own weight.
- Power to erode, transport, and deposit
Glaciers: how they form
- “excess” snow accumulates year after year, coming thicker and denser under its own weight.
- older snow layers are progressively buried by new snowfall, snow re-crystallizes to produce smaller, rounder, and denser crystals.
- This occurs by sublimation of moisture that is thenre-deposited.
Glaciers how they move
- internal deformation (plastic creep): individual crystal planes gliding past each other in response to stress as gravity acts on a large body of ice.
- A layer of meltwater at the bed of temperate glaciers provides lubrication, allowing the glacier to slide on its bed. This is called basal sliding.
- Cold: internal deformation, very high lat. or alt.
- Warm: basal sliding, faster than cold, more erosive
What are the Different Types of Glaciers
- Alpine glaciers: found in mountainous regions, their shape and flow pattern is strongly influenced by the topography.
- Cirque glaciers: occupy bowl shaped depressions on mountain sides formed by glacial erosion.
- Valley glaciers: occupy mountain valleys and may extend 100’s of km from cirque headwalls. Valley glaciers often represent thecoalescence of many smaller cirque and valley glaciers.
- Piedmont glaciers: valley glaciers that emerge from confining valleys and spread laterally to form fan-shaped lobes.
Temperate versus Polar Glaciers
- Temperate (warm) glaciers contain liquid water. This can be due to two reasons: either they experience above freezing temperatures during summer, or the ice is so thick that it is above the pressure melting point at the bed, producing a layer of meltwater.
- Polar (cold) glaciers are belowfreezing throughout and are frozen to their bed.
Glacial erosion, features and landscapes formed by glacial erosion
Glacial ice erodes bedrock surfaces by plucking and abrasion.
Plucking: breaking off of large chunks of rock from the down glacier (lee) side of rock outcrops along pre-existing joints or fractures in the rock.
crushing and grinding of rock into fine particles called glacial flour causing glacial polish (smoothing of bedrock surface)
bowl shaped depressions formed as a glacier cuts into the side of a mountain.Cirques have a broad, gently sloping bottom and a steep headwall.
alpine lakespartially filling the bowl-shaped depression at the bottom of a cirque
narrow, knife edge ridge that is left standing in nearly sheer relief as glaciers erode fromopposite sides of a mountain ridge
glaciers have cut completely through a ridge a u-shaped notch is left behind
a pyramid–shaped mountain peak leftby cirque glaciers cutting into three or more sides of a mountain
straight, wide valley with steep sides and a flat bottom. Formed when a glacier straightens and widens a narrow, v-shaped river valleys originally formed by stream erosion
left perched high above the main valley floor because smaller tributary glaciers have less erosive power than the main valley glacier. Hanging valleys often end in plunging waterfalls that drop to the main valley floor
U-shaped valleypartially drowned by seawater
- Poorly sorted material called till containing a wide range of particle sizes from finely ground glacial flour by abrasion to house sized boulders plucked from mountains.
- Till may also be shaped into streamlined hills called drumlins underneath continental ice sheets.
well sorted material as particles are sortedby size according to the energy of flowing water needed to move them
- piles of till that accumulates at the edge of a glacier when it remains in oneplace for some period of time.
- Lateral moraines: deposited along the side of a glacier
- Terminal (end) moraines: deposited at end of glacier
- Medial moraines: one glacier flow into another
Glacier mass balance:
how are they measured
- Difference between mass added to the glacier by accumulation and mass lost from the glacier by ablation. (accumulation - ablation)
- Changes from year to year in response to climate variability.
- Additions of mass to a glacier by snowfall or avalanche from adjacent valley walls.
- Area: portion of glacier with a net gain of mass.
- Loss of mass from a glacier by melting or glacier ends in a body of water, by calving of icebergs.
- Area: glacier with net loss of mass
how does a glacier respond to positive and negative mass balance
- Positive: more accumulation than ablation, expands in thickness and area.
- Negative: less accumulation than ablation, retreats in thickness and area.
Milankovitch cycles: what are they, how do they affect climate, configuration that favors glaciation, interglaciation
Eccentricity, Obliquity, and precession
changes in the shape of the Earth’s orbit, from an elliptical path to a more spherical path. To go from a more elliptical orbit to a less elliptical orbit and back again, takes about 100,000 years
- changes in the tilt of the Earth’s axis from about 22 degrees to 24.5 degrees.
- Cycle takes about 41,000 years to complete.
- The smaller the tilt, the less seasonal variation there is between summer and winter in middle and high latitudes
- as the Earth rotates on it axis, it wobbles like a spinning top, this cycle of about every 19,000-24,000 years.
- Affects the seasons by changing thetiming of summer and winter relative to the position of the earth in its orbit around the sun.
Evidence for glacier advance and retreat (changes in ice volume) on Milankovitch time scales
Glaciers represent the excess of winter snowfall over summer melting, minima in solar radiation in summer favors the growth and expansion of glaciers. Because most ofthe earth’s land area is in the Northern Hemisphere, it is minima in summer solar radiation in the Northern Hemisphere that favor glaciations. Minima in summer solar radiation occur when the eccentricity is low and axial tilt is low, resulting in less difference between the seasons and cooler summers.
- any body of water that flows in a channel.
- Part of the hydrologic cycle because they carry excess precipitation (runoff) to the ocean.
- Part of the rock cycle because they erode, transport, and deposit sediment
discharge and gradient
- Discharge = volume of water carried per unit time
- Gradient: change in elevation over some horizontal distance along the stream
- lowest point to which it can flow and erode.
- Large rivers:sea level
- Tributary streams: large river or lake
- Closed basins: elevation of basin floor
- Actively subsiding basins (arid climates): elevations lower than sea level.
meandering vs. braided
- Meandering: Mature streams have winding and sinuous channels that migrate across a floodplain by simultaneously eroding on the outside of bends and depositing on the inside of bends.
- Braided: stream’s flow divides into multiple and interconnected channels, carry more sediment as bed load, areas with highly variable discharge and abundant coarse sediment, developed downstream of glaciers
young vs. mature
- Young: stream with a steep gradient, rapidly due to the energy of the rapidly moving water, resulting in rugged topography, large drop in elevation from their source to their base level, fast velocities and coarse sediment load in the stream channel.
- Mature: Meandering streams, have a small elevation change and are close to their base level. Water velocities are slower and the channel sediment load is finer.
landscapes resulting from the deposition of sediment by streams. (stream partially loses its sediment carrying capacity due to a drop in velocity)
very rapid risein water levels over a very short period of time, a few hours or less, areas with impervious ground types, such as bare rock of desert canyons or the concretejungle of cities.
- Intense rainfall in a local area, shorter duration and affect a smaller area or smaller watershed.
- Localized nature of the excess runoff, upstream floods quickly recede over a period of a few days as the affected area drains away
Floods of a longer duration that affect a larger area and areproduced by persistent climate conditions, rise and fall over a periodof weeks or even months.
estimating discharge of floods of different recurrence intervals from stream discharge data
- Recurrence interval: how frequently a flood of a given severity occurs on average at a given location. calculate by the peak annual discharge of the stream.
- RI = (n +1)/m
- n: # of years of record
- m: rank of the peak annual discharge (large: 1)
what does the 100-year flood really mean
probability estimate, the longer the time period the greater the probability of seeing at least one 100 year flood.
- wave height: vertical difference between the crest and trough
- wave length: distance between successive crests
- wave period: time for successive wave crests or troughs to pass a point
wave translation and refraction
- Translation: shallow water, wave contact with bottom, circular orbits become elliptical orbits, wave length & velocity decreases while wave height increases. Period remains the same.
- Refraction: wave crests bends as they approach coastlines
- Series of waves strike a shoreline at an angle, they generate a current parallel to the shoreline.
- Develops as waves strike a shoreline at an angle, then wash straight back (perpendicular) due to gravity.
- Serves to redistribute sediment along a beach.
Coastal engineering structures
- Jetty/ groin: sand piles up "upstream" of theobstruction whereas areas "downstream" are robbed of their sediment supply. FAIL
- Seawalls: destroy a beach by focusing wave energy in one place as breakers crashagainst the seawall. FAIL.
- Beach nourishment: artificially supplying sediment to a beach. Sand is trucked inand placed on the beach or offshore sediment is dredged and pumped onto the beach. Success (Miami Beach)
Sea level change (local vs. eustatic)
- Eustatic: global change from change in volume of water in ocean/ volume of the ocean basins. (glaciers & ice sheets on land)
- Local: tectonic uplift/ subsidence of land surface
tsunami (causes, differences from wind-driven waves)
- Impulsively generated seismic sea waves produced by abrupt vertical displacement of ocean water. Tsunami are caused by earthquakes, submarine volcanic eruptions, submarine landslides, meteorite impact.
- VS. Wind Driven: Wind = break & retreat, Tsunami = straight, long wavelengths
- Saturation zone & aeration zone separated by a surfacecalled the water table.
- Saturation zone: area beneath the water table where allpore spaces are filled with water.
- Aeration zone (vadose zone):area above water table where pore spaces are filled with both water and air.
- Water table: upper surface of saturation zone or, alternatively, the lower surface of theaeration zone
gaining vs. losing streams
- Gaining: humid climate (water table close to ground surface) discharge zones for groundwater and are perennial or always flowing.
- Losing: arid regions (surface streams above water table) water leaks into the ground from their channels.
- Any material with sufficient porosity and permeability to deliver water at ausable rate.
- Porosity: total volume of pore space and is affected by size, shape, sorting, and arrangement of particles.
- Permeability: how easily a solid allows a liquid to flow through and is determined by the size and connectivity of pore spaces. Sand, gravel, and poorly cemented sandstones all make good aquifers because they have both high porosity and highpermeability.
Slope of the water table; the difference in water table elevation over some distance. Groundwater always flows down the hydraulic gradient Difference in water table elevation (h) over a specified distance (L).
Water use by sector and income
- sectors: agriculture (82), industry (4), domestic (2), reservoir (losses 12)
- Income: water use per captia (U.S. - 1600 cubic meters; 400,000 gallons), Haiti (10 cubic meters, 3000 gallons),
in stream vs. off stream use
- Instream: water that is used without being withdrawn from its source. (hydroelectric generation, navigation, fish and wildlife habitats, sediment transport, and recreation)
- Offstream: either removes or diverts the water. (Consumptive use,used by industry, irrigation, and households)
- groundwater withdrawal exceeds natural recharge rates and become nonrenewable resource. permanent reduction in the porosity of the aquifer and hence the volume of water the aquifer can hold.
- change the groundwater flow direction due to changes in the water table and cause desertification
- Eastern states where surface water is relatively abundant. Landowner ship.
- The right to use water is restricted to landowners immediately adjacent to the stream.
western states where surface watersupplies are insufficient to meet the demand for water. Appropriated (divided up) among different users (by volume).
Global energy resources
Renewable and non-renewable resources.
- non-renewable energy source (Coal, oil, and natural gas)
- Remains of plants and animals that, over millions of years, were transformed into coal and oil by heat and pressure.
- Non-renewable: Nuclear fission, Geothermal, nuclear fusion.
- Renewable: Biomass fuels, Hydropower, wind, solar, and tidal power.
replenished at a rate greater than the rate at which they are used.
developed vs. developing countries: energy supply
- Fossil fuel account for 80% use in people in developed countries.
- Developing countries: firewood, charcoal, animal and crop (biomass fuel)
Altered plant residue that grew in ancient freshwater or brackish-water swamps, typicallyfound in estuaries, coastal lagoons, and low- lying coastal plains or deltas. 38 out of 50 states; 1/4 (US).
liquid composed of many different, heavier hydrocarbons compounds that are separated at refineries to make gasoline, diesel, kerosene, lubricating oils, and tars. formed from the remains of marine microorganisms(plankton) that are rich in lipids, protein, and carbohydrates.
Methane production occurs by anaerobic bacteria in this setting. formed from the remains of marine microorganisms(plankton) that are rich in lipids, protein, and carbohydrates.
Environmental impacts of fossil fuel use
- Coal: acid mine drainage, air pollution
- Oil & Natural Gas: land disturbance, drilling issue, fires, oil spills, air pollution.
The United States oil supply
- Oil production 32% of U.S. oil demand, 39% petroleium US energy supply, natural gas and coal 22-23%. 2007 oil imported from 68 foreign to U.S. (canada & mexico).
- 13 % of U.S. oil from Persian Gulf (2/3) global supply. 59% of Persian Gulf oil exported to Japan.
point in time when extraction of oil from the earth reaches its highest rate and then begins to decline.
The future of fossil fuels
Hydropower and nuclear power.
Types and sources of air pollution
- Primary pollutants are emitteddirectly into the air. (SO2, NOx, CO, CFCs, CO2, and black carbon (soot) aerosol)
- Secondary pollutants are produced by chemical reactions in the atmosphere involving primarypollutants. (sulfate and nitrate aerosols and ozone)
- Anthropogenic sources ofpollutants include emissions from motor vehicles (NOx), emissions from coal burning powerplants (SO2).
- Stationary sources are point sources with a defined location. (power plants factories, and construction sites)
- Mobile sources are moving sources such as cars, trucks, and airplanes.
Meteorological impacts on air quality
Wind direction and speed. High winds are able to diluteair pollutants more effectively, and wind direction influences where emissions will go.
a layer of cold dense area near or at the surface with warmer, lighter air aloft (trapped near the ground)
mix of air pollutants whose chemical reactions are driven byenergy from the sun. loss of visibility caused by suspended particles (aerosols) which scatter light,giving the atmosphere a “hazy” appearance.
acid rain formation
Regional to global environmental problem related to the burning of fossil fuels. Results from sulfur dioxide emitted from power plants, but is also caused by nitrogen oxides from automobiles.
Earth's radiation budget
balance between incoming solar radiation and outgoing terrestrial radiation. Earth’s atmosphere and surface absorbs and is warmed by solar radiation. This energy is then re-emitted by the earth back to space, but at longer wavelengths.
shortwave (solar) vs. longwave terrestrial radiation
- Short wavelength (solar radiation), primarily in the visible and ultraviolet portions of the electromagnetic spectrum. Solar radiation is absorbed by the earth and reemitted as longer wavelength terrestrial radiation.
- The escape of geothermal heat at Earth’s surface from its interior is insignificant compared to the amount of energy from the sun that is absorbedby earth’s surface and atmosphere.
Only a fraction (70%) of the solar energy received by the Earth is absorbed by theatmosphere or surface of the Earth and causes warming. The rest (30%) of the solar energy is directly reflected back into space either by clouds or by the surface of the Earth without being used to heat the planet
the greenhouse effect
heat is trapped in the lower atmosphere by certain types of gases in the atmosphere called greenhouse gases. transparent to incoming shortwave solar radiation.
change in the amount of incoming solar radiation or a changein the amount of outgoing terrestrial radiation. affect the amount of solar radiation reaching the surface.
Greenhouse gases: what are they and how do they work, types of greenhouse gases and where do they come from
- largely transparent to incoming shortwave radiation from Sun. By increasing greenhouse gas concentrations, more infrared radiation isabsorbed, increasing surface temperatures.
- Gases: carbon dioxide, methane, and water vapor, nitrous oxide, and oxygen
Nuclear energy: fission vs. fusion
- Nuclear fission: splitting of heavyatoms to make lighter atoms, artifically acceleration of radioactive decay (free neutron strikes an atom, breaking into smaller atoms)
- Nuclear fusion: energy source that is essentially inexhaustible
breeder vs. burner reactors
- Burner reactors: reactors that consume more fissionable material than they produce and rely solely on the fission of 235 U. 238 U not fissionable convert to Pu239 by neutron bombardment.
- Breeder reactors: used to conserve 235 U by surrounding a fissionable core of 235U with a fertile material 238U
Types of radioactive decay
- Alpha decay: ejection of an alpha particle from the radioactive nucleus. (consists of two protons and two neutrons (helium nucleus), results in new element changes the number of protons in the nucleus.
- Beta decay: ejection of high energy electrons from the nucleus when a neutron decays to a proton and electron. changes the number of protons, resulting in a new element.
- Gamma decay: emission of high energy electromagnetic radiation from the nucleus.
Low-level radioactive waste
- small amounts of radio active substances. alpha particles and have short half lives.
- burial of low level: dry climate with low rate of water infiltration and a deep water table.
High level radioactive waste
- Real threat to human health and the environment. beta or gamma. problematic to store, contain and dispose of.
- Should be isolated for at least 10 half-lives.
- waste from nuclear power plants and high level waste
- Favorable: federal lands, low rainfall and infiltration rates, 300 m depth to water table, strong rock.
- Unfavorable: local opposition, fractures in host rock, infiltration and groundwater movement, volcanic activity, earthquakes, and habitat destruction.
- Energy from the Sun is used to make electricity with photovoltaic cells, a device that converts photons from the sun (light) into electricity. Sun used for space and water heating. Passive = stores. Active = movement.
- Advantages: free energy, quick installation, no CO2 emissions, no air/water pollution.
- Disadvan: 60% sun, blockage, need heat storage system, costs.
- motion of air turbines and generate electricity.
- Advantages: quick construction, easy expansion, high efficiency, low operating costs, no pollutants.
- Disadvan: steady winds, backup storage, migrating birds, land
building dams with generating turbines and water storage (wave and tidal energy).
- space heating and cooking, undeveloped countries.
- Advantages: large supply, moderate cost, no CO2 emissions.
- Disadvan: low photosynthetic efficiency, competition for agricultural lands.