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Geology Ch. 19


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What are the major uses for water?
Agriculture, irrigation, industry, household uses.
Where is most freshwater found?
What are the major sources of water we use?
seawater (can’t use), glacial ice caps, underground (too salty, too deep), lakes & streams
What are the characteristics of a good aquifer?
High porosity, high permeability
What types of rocks make good aquifers?
Sandstones and carbonates
What is porosity?
volume of a rock not occupied by solid, volume of empty space in a material
What is permeability?
solids ability to allow liquid to pass through it, ability of material to allow fluids to pass through an interconnected network of pores
How do characteristics of the rock (grain size, sorting, grain shape, etc) affect porosity?
Well sorted-high porosity, more rounded-high porosity, bigger size-more porosity
What geologic processes affect porosity (fracture, cementation, etc.) and how do they affect it?
Fracture and dissolution increase secondary porosity

Cementation, compaction, lithification decrease primary porosity
What is primary porosity? Secondary porosity?
Primary-space that remains between solids grains or crystals immediately after a sediment accumulates or a rock forms
Secondary-new pore space in rocks created sometime after a rock first forms
How does pumping affect the water table?
Lowers locally and creates cone shape
Be able to speculate where springs might be located.
-Where ground surface intersects the water table in a discharge area, such springs typically emit water upward into rivers, ponds, or valley floors
-where a perched water table intersects the surface of a hill
-where downward-percolating water runs into a continuous impermeable layer and migrates along the top surface of the layer to a hillslope
-where a particularly permeable layer or zone intersects the surface of a hill, water percolates down through the hill and then migrates along the permeable layer to the hill face
-where a network of interconnected fractures channels groundwater to the surface of a hill
-where flowing groundwater collides with a steep impermeable barrier, and pressure pushes it up to the ground along the barrier, faulting can create such barriers by juxtaposing impermeable rock against permeable rock
-ARTESIAN SPRINGS form if the ground surface intersects a natural fracture (joint) that taps a confined aquifer in which the pressure is sufficient to drive the water to the surface
Know how vertical drop, distance of flow, hydraulic conductivity affect flow rate.
Hydraulic gradient increases-rate increases. Steeper slope-faster flow. Vertical drop/flow distance = rate. Hydraluic conductivity (K) includes permeability and fluid viscosity and the higher the K, the faster the rate.
What is a karst terrane? How does it form? What types of rocks? What types of land forms and geological features does it include?
Landscape where caves develop. Made of limestone. Water table and limestone. Cave network forms. Water table drops. Sink hole roof collapses.
hydraulic gradient
slope of water table (change in H over d)
Darcy’s law
Equation that states the amount of water passing through an area depends on hydraulic conductivity and the gradient

Q=K*(H/D)* A

Q=volume of water passing through area
K=hydraulic conductivity, permeability and viscosity
A=cross sectional area
quantity of ground water that lies above regular water table because lens under it is impermeable and prevents water from sinking down to water table
well where water rises on its own
sediment or rock that doesn’t transmit water
Unconfined aquifers
layer of water just below earth’s surface and below porous layers that rain water can seep into
sediment or rock that transmits water easily
phase of lithification where cement which consists of mineral that precipitate from ground water fills space between clasts and attaches grains together, after this occurs, no longer porous
groundwater table
boundary between pores full of air and pores of water, approx. parallel to ground
word used to talk about water above level of ground water in unsaturated zone
page 19, groundwater

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