Exam 3 part 3 Flashcards
What are the two possible methods of stream formation?
1) Antecedent stream
2) Superposed stream
What is an antecedent stream?
It’s a stream that existed before the ridge was formed
What is a Superposed stream?
A stream let down upon a preexisting structure
What would we do with water gaps?
We would build trains and roads to follow the gaps for convince
What is the most common and most destructive geological hazard?
Floods
What are 4 types of floods?
1) Regional floods (Flat land)
2) Flash floods (V-shaped)
3) Ice-jam floods (Broken ice on river
4) Dam failure (humans dammit)
What are four different ways to control floods?
1) Engineering efforts
2) Artifical Levees
3) Flood-Control dams
4) Channelization
What is the largest reservoir of fresh water available to humans?
Ground water
Where is ground water found?
It is found in the pores of soil and sediment plus narrow fractures in bedrock
What is the difference between ground water and the zone of saturation?
They are the same thing
If you remove ground water, what do you risk?
You risk:
Creating sinkholes
Creating Caverns
Upsetting the balance of stream flow
Is soil moisture ground water?
No.
What is soil moisture?
Water held by molecular attachment on soil particles in the near-surface zone
How is the saturation zone created?
Through water the percolates downwards to the water table, it reaches a zone where sediment and rock are completely filled with water
Where is the water table?
It is located between the zone of aeration (vadose zone) and the saturation zone. It is the upper limit of the zone of saturation
Is ground water still?
No
What is the capillary fringe?
It a zone just above the water table, it extends upwards to fill in pores
How is ground water held in?
By surface tension
What is the zone of Aeration?
It is the zone below the belt of soil moisture and above the water table, includes the capillary fringe.
Can you find ground water in the desert?
Yes
Can the water table vary?
Yes, it can vary from depth as well as seasonably and from year to year
What is the water tables shape?
Usually a replica of the surface topography
How can streams interact with ground water?
A stream can gain water from ground water through the stream bed or it can lose water to ground water through the stream bed, there’s also in some cases where it can lose in some places and gain in others
What is the percentage defintion of porosity?
Percentage of total volume of rock or sediment that consists of pore spaces
How do you calculate porosity?
Pore volume / total volume
If the porosity is above 50% then what happens to the grains?
They no longer touch each other
What is an aquitard?
An aquitard is a zone within the Earth that restricts the flow of groundwater from one aquifer to another. (Such as clay)
What is an aquifer?
Permeable rock strata or sediment that transmits ground water freely (Such as sand and gravels)
How quickly does ground water move?
Not quickly, few centimeters a day
What is Darcy’s law?
The law says that if permeability stays the same then ground water movement will increase if the slope increases
What moves ground water?
1) Darcy’s law
2) Hydraulic head/gravity
What is the hydraulic head?
It’s the vertical difference between the recharge and discharge points, The larger the gradient the more gravity
How is the movement of ground water measured?
1) Colored dyes
2) Carbon 14
How do springs occur?
When the water table intersects with the earth’s surface, it’s a natural outflow of groundwater
What is a localized zone of saturation?
A perched water table
How is a perched water table created?
By an aquitard
How warm are hot springs?
They are 6-9 degrees hotter than the mean annual temperature of the locality
How is water for hot springs warmed?
Through cooling igneous rock
Where does the water from the hot springs come from?
Precipitation that gets heated through thermal heating
Where do geysers occur?
When there is extensive underground chambers that exist with hot igneous rock
In the west ground water gets heat from igneous rocks but what about the east?
They get their heat from the geothermal gradient
What accumulates near the surface at the geysers?
Chemical sedimentary rocks
1) Siliceous sinther
2) Travertine
What is cone of depression?
When some one pumps the wells to the point that the water table lowers
What is an artesian well?
A situation where ground water under pressure rises above the level of the aquifer
What are the two types of artesian wells and what’s the difference between them?
Non-flowing: Pressure surface is below the ground
flowing: Pressure surface is above the ground
What is subsidence?
When the ground sinks after the water is pumped from wells faster than natural recharge processes can replace it
What is salt water contamination?
Excessive groundwater withdrawal causes salt water to be drawn into wells.
What is a common groundwater contamination problem besides salt water?
Sewage, some aquifers with extremely permeable rock can cause ground water to go great distances without being cleaned
