geology final exam Flashcards
What fraction of Earth’s water resources are represented by groundwater?
~0.6% of all water, 30.8 % of fresh water
How much of the freshwater available is groundwater?
~30.8%
What are two factors that determine how much water can be stored in Earth and how much can move through Earth? Define them.
Porosity: amount of void space that water can store
Permeability: ability of a fluid to move through pores
What are the best earth materials for storing and moving groundwater?
Alluvial materials: gravels, sands
How does water enter the groundwater system?
Permeable layers
What’s the water table?
The top surface of the saturated zone in the subsurface.
What do the following terms mean: aquifer, aquitard, and aquiclude?
aquifer: transmits fluid readily/easily
aquitard: hold water, do not readily transmit water (ex: clay, shales, etc.)
aquiclude: does not allow water to pass through.
What makes a good aquifer?
Permeability, connectivity of pore spaces (pathway for fluid to travel)
Confined vs unconfined aquifers
Unconfined: open to the surface
Confined: confining layer above the aquifer that does not allow it to be open to the surface.
Describe what a well is:
Tube in a borehole with a screen opening to the subsurface
Describe artesian wells…why do they exist?
Areas where groundwater is under pressure. This can often happen to confined aquifers.
What does a hydrogeologist mean by “head”? What are the two components of that measurement?
Elevation + Water pressure = capacity for water flow
where elevation is height above sea level, and water pressure is how high up the water is pushing toward the surface.
How and why does a “cone of depression” form on the water table?
pumping; removing the water from the system
Describe the most typical sources of groundwater contamination:
industrial (leaking tanks), agricultural (fertilizers), and municipal (waste dumps) environments, stormwater
How much of Earth’s water is easily accessible freshwater?
~0.3%
What causes the effects of natural water shortages to be multiplied?
1) Slow recharge/recovery rate, 2) economic disadvantages
Water has a special property that causes one side of the molecule to have a negative charge and the other to be positive. What is this property called?
polarity
What does polarity allow water to do?
form bonds, “universal solvent”
What are three additional special properties of water?
high specific heat (hard to heat up and cool down); lower density as a solid (ice floats); and it exists in all 3 phases regularly.
The hydrologic cycle is powered by the ____.
sun
What are the two major fluxes in the hydrologic cycle?
precipitation and evaporation.
What are the four factors that cause the cycle to vary in its flux from place to place?
latitude, elevation, climate (winds), and seasonal changes
Contrast “withdrawn water” with “consumed water”
withdrawn water: total water withdrawn from source (not necessarily water lost)
consumed water: total water withdrawn from source and not returned (water lost)
What two sectors use the most water on the planet?
industrial and agriculture
For each of these two sectors, give examples of products that consume the most water.
automobiles and beef
Domestically, what uses the highest proportion of water on a daily basis? Second highest?
Toilets; showers; then faucets
Water is not evenly distributed around the world. What factors influence the supply of water in a place?
weather, surface geology, subsurface geology.
The impacts of water shortages can be immense. What are four impacts that are commonly seen around the world?
economic loss, famine, refugees, and wars
Where is most of Earth’s freshwater held, and how much is held there?
Glaciers/permanent snow: ~68.9% of freshwater, actual amount ~24,000,000 km cubed
How much is held by lakes and streams?
0.3% or ~100,000 km cubed
Discharge of the Nile vs the Amazon and why they differ?
2,830 meters cubed/second vs 209,000 meters cubed/second. Basin size and average precipitation causes differences in discharge amounts.
What is a drainage basin and divide? Given an example.
drainage basin: the land area drained by a stream and its tributaries
divide: the boundary (ridge) separating one drainage basin from another. One example is the Rocky mountains.
Streams have a beginning called the ____, and an end called the _____. Eventually they all reach the lowest level to which they can flow, called the _____.
headwaters; mouth; and base level (ocean)
A stream profile shows the elevation of a stream along its course. Why does profile matter?
Slope affects velocity. Velocity controls competence (ability to carry sediment)
In headwaters of a stream, what is the dominant process?
Erosion/transport