Geology 103 Final

freshwater

2 percent is stored in ice
1.9 percent of freshwater is accessible
97.4 of the earth's water in the ocean (saltwater)

hydrologic cycle

groundwater is a component of the hydrologic cycle
1.evaporation
2. transpiration
3. precipitation
4. infiltration
5. runoff

porosity

percent of pore spaces
pore- open space within sediment or rock

impermeable

pores isolated, not connected

permeable

pores connected

aquifer

sediments w high porosity and permeability
sandstone, gravel, limestone, fractured granite

aquitard

sediments that have low permeability
shale/clay
crystalline rocks such as granite and schist

unconfined

intersects the surface
contact w atmosphere
easily contaminated
easily recharged by water migrating freely down from surface

confined

aquifer beneath the aquitard
isolated from surface
less susceptible to pollution

water table

-boundary between saturated and unsaturated
-subsurface boundary

depth of water table is variable

humid- closer to surface
arid- tens to hundreds of meters down
rainy periods- water table rises
droughts- water table falls

perched water table

lens shaped aquitards in the subsurface
overlie unsaturated material
represent a "false" water table

topography of water table

mimics the topography of the land

groundwater flow

groundwater infiltrates through *recharge* areas
exits at the subsurface at the *discharge* areas

scales of groundwater flow

local- shallow flow over short times and distances
intermediate- flow of moderate, depth, time and distance
regional- deep, long distance, long-duration flow

hydraulic gradient

change in hydraulic elevation
elevational change over horizontal distance
steeper- faster flow
less steep- shorter flow

groundwater flow governed by

permeability
high permeability- inc rate of groundwater flow
low permeability- decreases rate of groundwater flow

wells

drilled into the saturated zone
holes excavated or drilled to obtain water
water is recovered by lifting or pumping
drawdown occurs if removal exceeds flow to the well

cone of depression

water table near the well drops forming cone of depression
cone may expand outward with continued pumping
pumping from multiple wells in an area is additive

artesian well

drill into confined tilted aquifer
water rises without pumping to a level below the aquifer
a sloping aquitard
tapping into source where water is already flowing

water distribution systems

water pumped into an elevated storage tank
elevation creates an artificial potentiometric surface
pressure drives water through the distribution center

springs

springs result from varies geologic features
where the water table intersects the land surface
contact between high and low permeability layers
can be caused by fractures or faults
perched water table
cracks provide a pathway to form an artesian spring

oases

in sahara develop from spring flow
water from recharge areas flows to oasis discharge points
locations have been culturally important for thousands of years

hot springs and geysers

very hot rock in a region that has igneous activity (magma chamber) lies close to surface and heats groundwater

groundwater problems

cannot be replenished quickly
mismanagement
overuse
pollution

depletion

severe water table decline can alter surface water flow
by capturing flow, wells may dewater streams and lakes
esp problematic in arid and semi-arid regions
everglades example

great plains aquifer

groundwater withdrawal from this unconfined aquifer has lowered the water table over 150ft in places

subsidence

water in pore space holds grains apart;
when water is removed:
sediment grains compress; pore spaces collapse
the land surface cracks and sinks
subsidence is mostly irreversible

dramatic examples of subsidence

leaning tower of pisa
sinking buildings in venice italy
the san joaquin valley, ca

groundwater depletion prevention methods

redirecting surface water into recharge areas or pumping it back into the ground
examples: parks restructure land to catch runoff and funnel it to a stormwater/catchment pond

groundwater contamination

cones of depression are capable of altering flow
excessive pumping can reverse natural hydraulic agent
expanding cone may capture pollutants

saline intrusion

saltwater intrusion renders the water unpotable
beneath coastal land, freshwater floats on saltwater
pumping causes the fresh/salt boundary to rise
eventually, saltwater may enter the pumping well

point sources

easily identifiable specific sources
industrial sewage, pipes, tanks, mines

non-point sources

hard to identify
spread out and intermittent like oil from parking lots
difficult to trace and regulate
many everyday activities contribute to non point source pollution

water quality and pollution

cholera in london

contamination sources

fertilizers
pesticides
bacteria

nutrients

fertilizers, detergents (phosphorus and nitrogen)
cause explosive growth of algae
block sunlight and kill bottom plants
consume oxygen when they die
cause methemoglobinemia (blue baby syndrome)

biochemical oxygen demand (BOD)

aerobic bacteria use oxygen while consuming organic matter
deplete oxygen in water and suffocate other organisms
eutrophication
agriculture and urban sewage add organic matter to water
dead zones

natural groundwater

often of high quality
filtering effect of porous material removes particulates
clay minerals can absorb certain dissolved ions
natural groundwater may contain unwanted substances;
minerals that cause hardness
dissolved iron, manganese, hydrogen sulfide gas, dissolved arsenic

hardness

dissolution of carbonates adds ca2+ and mg2+
in excess these cations;
reduce the effectiveness of soap
precipitate in plumping to create flow clogging scale
hardness is mitigated by ion exchange (water softening)

iron and manganese

derived from rock weathering
occur in reducing o2 poor groundwater
cause taste and odor problems, stain plumbing and laundry

hydrogen sulfide-rotten egg gas

contributes to taste and odor problems
commonly associated with high iron and manganese

arsenic

naturally occurring poison
derived from weathering of pyrite bearing sediments and metamorphic equivalents
silica rich volcanic ash deposits
EPA maximum contaminant limit is 10ug/L (ppb)

sanitary wastes

failing septic systems
animal feedlot runoff
contribute bacteria and viruses

pathogenic organisms

microbes that cause disease (cholera, typhoid, dysentery)
difficult to measure in water
fecal coliform bacteria (mammal gut bacteria) measured instead (easier)

toxic chemicals

petroleum storage
underground storage tanks
gas stations
petroleum terminals
industrial wastes
paint and thinners
degreasers and solvents
landfill leachate
mining wastes

acid mine drainage

weathering of coal and metal ores produces sulfuric acid
runoff from abandoned mines acidic or contains heavy metals
lead mercury zinc
naturally present in SMALL quantities
bio magnification

treatment of contamination

possible but expensive
most remedial strategies include removing the source
pump and treat
votalize and vaporize
steam clean
bio remediation utilizes bacteria to clean groundwater
wastewater treatment plants
-remove contaminants from urban sewage

septic tank system

treating wastewater in rural areas
solids removed by settling and bacteria
water filtered and soaks into soil
works best where geology also filters water

wetlands as wastewater treatment

wetlands are natural filters of water
wastewater rich in fertilizer promotes plant growth
artificial wetlands used to clean out fertilizers

karst topography: caves and sinkholes

case: winter park, florida
groundwater slowly dissolved limestone bedrock forming a cavern that collapsed inward
many sinkholes fill w groundwater, forming lakes
groundwater is weakly acidic
co2 reacts with water to form carbonic acid
co2 added to rainwater as it falls through the air

karst landforms

limestone dissolution creates unique karst landscapes
disappearing streams
natural bridges
towers
caves
sinkholes
springs

karst development

groundwater moving down thru the first cave
continued dissolution results in eventual roof collapse
process creates sinkholes and troughs
remnant limestone forms ridges, hills, natural bridges
sinkholes result from roof collapse, dot large regions of karst landscapes

mineral

naturally occurring
solid
crystalline structure
definite chemical composition
primarily inorganic

silicate minerals

silicates are the most common minerals on earth
make up the earths continental and oceanic crust
quartz, feldspar, clays

oxides

o2-
magnetite
hematite
rutile

sulfides

pyrite (iron)
galena (lead)
sphalerite (sulphur, zinc)

carbonates

co32-
calcite

sulfates

many form by evaporation of seawater
gypsum

native metals

pure masses of a single metal
copper gold silver

where are ore deposits found

where igneous and hydrothermal activity occur
plate boundaries
along rifts
hot spots

ore deposits: igneous processes

deposits tend to be veins

ore deposits: metamorphic processes

regional metamorphism
continental collision increases pressure and new minerals form
asbestos, talc, etc

contact metamorphism

heat from magma intrusion from metamorphoses surrounding rock and new minerals form
garnets

sedimentary processes

sand
gravel
clays
conglomerates
shales
evaporites: minerals left when water evaporates
-halites
-gypsum

biological processes

minerals derived from organisms
calcium and magnesium carbonates such as limestone, form in marine organism shells
calcium phosphate forms in bones

weathering in tropical areas

weathering in tropical areas
bauxite (aluminum ore) comes from weathering of igneous rocks that leave aluminum minerals

mining

mining impacts
-modify landscape
tailings
-modification of river stream drainages
lowered groundwater surface during mining leads to artificial lakes in abandoned open-pit mines
abandoned mine land

underground mining

water contamination
chemicals leak from mine sites into ground
(cyanide used to extract minerals)
acid mine drainage

mine tailings

minerals left behind in the slurry after flotation (quartz, pyrite)
commonly contain large amounts of sulfide material
sulfides cause extremely acid waters in runoff

surface mining control

reclamation act of 1977
regulates mining practices and impacts on the environment
requires that land disturbed by mining be restored after mining is done

environmental regulations

clean air act
biotechnology to treat mining waste
recycling- reduce amount of mineral resource needed

wetlands to cleanup mine wastewater

shallow ponds lined with compost, topsoil, and limestone
plants
bacteria in compost

climate

average weather over a long period of time

weather

characteristics of the atmosphere over a short period of time, usually no more than a few days

factors that control major changes in global climate

solar radiation
atmospheric gas composition
albedo (earth's reflectivity)
plate tectonics
-volcanism
-ocean circulation

two important greenhouse gases

carbon dioxide co2
-volcanism
-respiration
methane ch4
-bacteria respiration
-anoxic decomposition

chemical composition of the atmosphere

nitrogen
oxygen
argon
carbon dioxide
water vapor

greenhouse effect

some of the infrared radiation from the Sun passes through the atmosphere, but most is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds. The effect of this is to warm the Earth's surface and the lower atmosphere.

importance of greenhouse gases

without greenhouse gas -.4 f
actual surface temp 59f
greenhouse warning 91f

albedo

fraction of solar energy (shortwave radiation) reflected from the earth back into space

fast vs slow sea floor spreading

fast= more co2 produced
climate= warmer
slower = less co2 produced
climate= cooler

flood basalts

large, long term volcanism causes warming

mountains effect climate

higher mts= more snow, increased albedo
weathering= co2+h20= carbonic acid
carbonic acid weathers the rocks

wilson cycle

The Wilson Cycle is a model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents.

super continent cycle - wilson cycle 400-500 million

opening
geologically active
more co2 climates warmer
shallow basins
sea level higher

closing phase

geologically less active
less co2 input, sea level lower
atmospheric and cooling glaciation

warming

spreading apart again

glaciers advance

changes in earths orbit act as a pacemaker for glaciers
glaciers advance when more snow accumulates in winter than melts in summer

ice growth configuration

low tilt of earths axis
little change in temp between seasons
warmer winter- cooler summer

ice decay configuration

high tilt of earths axis
large differences in temperature betwen seasons
warmer summers, cooler winters

last glacial max

18,000 bp
global temp down 4 celcius

how do we know about past climate

sediment and ice cores
real time monitoring
math and computer models

permafrost

emission of methane increase as much as two thirds over 1970 emissions

sea ice

reduction of albedo = increased warming

albedo

fraction of solar energy (shortwave radiation) reflected from earth back into space

fast vs slow sea floor spreading

fast = more co2, climate warmer
slower= less co2, climate cooler

flood basalts

large, long term volcanism causes warming