Geology 101 Quiz 11 Flashcards
water and weathering
water makes dissolution possible, expanding ice widens cracks, and glaciers can pluck boulders from mountain sides and pulverize them
water and erosion
rivers and glaciers transport weathered rock great distances
water and rock formation: igneous rock
water lowers the melting temperature and influences the rate of crystal growth
water and rock formation: metamorphic rock
water facilitates exchange with dissolved ions (hydrothermal)
water and rock formation: sedimentary rock
water transports dissolved and particulate minerals, and creates depositional environments
water and volcanism
water affects viscosity of magma and gas pressure
water and slope stability
water usually decreases the stability of a slope
life is possible in large because
water is liquid in the 0-100*C temperature range
unique properties of water
- melting-boiling temperatures 0-100*C
- polar molecule
- solid water is less dense than liquid water
- unusually high heat capacity
water has a ? structure; its peculiar shape results in ?
bent; a negative and positive side
the polar nature of water results in
- dissolution and transport of ions
- creation of surface tension
- attraction to sediment particles
the polar nature of water and its dissolution and transport of ions means water
increases weathering and assists in moving nutrients in and wastes out of organisms
the polar nature of water and the creation of surface tension means water
reduces evaporation rates and creates an entire habitat for surface organisms
the polar nature of water and its attraction to sediment particles means water
makes sediment particles stick together and causes capillary rise
many nutrients and waste products in organisms are ions, which means they are
easily dissolved and transported into and out of organisms
non-polar liquids like gasoline are good at dissolving ?, but not very good at dissolving ?
uncharged organic molecules; charged ions found in minerals
polarity creates surface tension because
the negative and positive sides of water molecules align to form weak bonds at the surface
one good thing that comes from surface tension is that evaporation is slower - why?
water has to break free from the surface tension to pass into the vapor phase
one good thing that comes from surface tension is that water striders can be water striders - how?
surface tension will support the weight of dense objects that will sink if they break through the surface tension; water striders take advantage of surface tension to walk on water
capillary rise
water is drawn upward into unsaturated sediments
where groundwater is shallow, roots can get water delivered by ? even if the roots do not extend to the water table
capillary rise
ice is less dense than water, and therefore floats, because of
the particular arrangement of water molecules in ice
water has an unusually high heat capacity, meaning
it takes more heat energy to raise the temperature of water compared to other substances
the heat capacity of water plays an important role in
climate control
over large bodies of water, heat exchange between the air and water changes the temperature of the ? more
air
only about ? of the earth’s water supply is available to drink, and most of this is sitting underground
1%
despite contamination, we still have water to drink because
water on earth does not exist in a static condition
water is continuously cycled and purified through what is called the
hydrologic cycle
hydrologic cycle steps
evaporation, condensation, precipitation, infiltration, evapotranspiration
transpiration
transfer of water to the atmosphere through leaves
if water filled plant cells and stopped, the flow of nutrients would stop - what keeps the water flowing through the plant?
transpiration
does water vapor automatically precipitate?
no
for precipitation, conditions in the atmosphere have to change to cause the water vapor to condense - this generally happens by
b
there are three common ways an air mass gets cooled, but all have to do with
the air cooling as it expands (as an air mass rises, it expands)
what are the three common ways an air mass gets cooled?
- orographic lifting
- frontal lifting
- convective lifting
orographic lifting
caused by an air flow over mountains
rain shadow
dry region on downward side of mountain range because air rising on the upwind side rains out as it rises; as air travels down the far side, it compresses and warms so no more water condenses
frontal lifting
caused by moving cold or warm fronts
cold front
cold air is more dense, so it ploughs its way underneath warmer air in front of it; as the warmer air rises, it expands, cools, and precipitates
warm front
warm air is less dense, so it slides up over the top of the colder air in front of it; as the warmer air rises, it expands, cools, and precipitates
convective lifting
caused by heating air near the ground
convective lifting is often associated with
cities where building and pavement absorb sunlight and radiate it out as heat
water that stays in the ground is known as
groundwater
groundwater can be divided into two regions
the saturated zone and the unsaturated zone
unsaturated zone
contains air and water in pores (a well in the unsaturated zone will be dry)
saturated zone
pores are completely filled with water (a well completed in the saturated zone will fill with water)
water table
top of unconfined saturated zone
aquifer
a geologic unit that transmits water in sufficient quantity to supply a well
confined aquifer
aquifer bounded on top by an impermeable layer
artesian well
water rises in a well above the top of the aquifer
flowing artesian well
water rises above the ground surface
potentiometric surface
the height to which water will rise in a cased well
influences on groundwater flow: porosity
ratio of pore volume to total volume (ex: if solid particles fill half the total volume, the porosity is 0.5 or 50%)
influences on groundwater flow: permeability
ability of a medium to transmit a fluid (water)
we tend to think that higher porosity always leads to higher permeability - is this true?
often, but not always
poorly sorted sediments have (lower/higher) porosity and (lower/higher) permeability
lower; lower
more compacted, more tightly packed sediments have (lower/higher) porosity and (lower/higher) permeability
lower; lower
tightly packed sand has a (lower/higher) porosity than loosely packed clay, and a (lower/higher) permeability
lower; higher
if the shape and packing are the same, different grain sizes (do/do not) change the porosity
do not
smaller particles will (decrease/increase) permeability and why?
decrease; because of attraction between the water and solid surfaces
good aquifers (high porosity and permeability) examples
sand, gravel, sandstone, karst limestone
karst
lots of dissolved caves and passageways
intermediate to poor aquifers
silt, glacial till, fractured rock, unweathered limestone
not aquifers
clay, shale, unfractured crystalline rock
one way a spring can form: if water accumulates on an impermeable layer intersected by a slope, water will
eventually seep out the side of the hill slope
one way a spring can form: fractures cutting through a confined aquifer will
provide conduits for pressurized water to reach the surface
when we start to pump water from a well, what happens to the water table or potentiometric surface?
a cone of depression (drawdown cone) forms
if pumping from multiple wells exceed annual recharge, the entire water table will begin to ?, which increases pumping costs and can cause ?
lower; wells to go dry and the ground surface to subside
subsidence
decrease in surface elevation due to collapse or compression of underlying material
subsidence in unconfined aquifers: draining water from unconsolidated sediments often causes ?, so the ground surface settles downward
compaction (compacted sediments take up less space)
subsidence in confined aquifers: confined aquifers are ?, but pumping relieves pressure, which allows the aquifer to ?
pressurized; compress (the ground surface drops)
subsidence in caves
a cave with a thin or weak roof may collapse if pumping drops the water level below the top of the cave
a depression or hole caused by a collapsed cave roof is called
a sinkhole
total dissolved solids (TDS)
the total mass of all dissolved ions and molecules per liter of solution
we divide water into different types based on TDS:
fresh, brackish, saline, brine
water in quartz sand (SiO2) tends to have (low/high) TDS< with dissolved ? as primary ion
low; silica
water in limestone (CaCO3) is fresh, but tends to have (lower/higher) TDS, with ? and ? as primary ions
higher; calcium and bicarbonate
water in halite (NaCl) forms a brine, (very low/very high) in TDS, with ? and ? as primary ions
very high; sodium and chloride
contaminants come in a variety of different forms
salts, metals, bacteria, agricultural and pharmaceutical chemicals, radioactive waste, organic liquids
organic liquids are divided into two groups
LNAPL and DNAPL
LNAPL
light non-aqueous phase liquid (floats on water)
DNAPL
dense non-aqueous phase liquid (sinks in water)
Which are harder to clean up and why? (LNAPL or DNAPL)
DNAPL because they continue moving downward in an aquifer and get hung up in little pools wherever the permeability is slow
