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44 Cards in this Set
- Front
- Back
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sinkholes are . . .
they form . . . |
caves that collapse,
Karst topography |
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porous rocks
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vesicular basalt (20%)
limestone (25%) well-sorted eolian sandstone (30%) conglomerate unconformity (30%) poorly sorted sandstone (15%) |
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low porosity rock
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granite (< 1%)
shale (5%) |
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primary porosity
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space that remains between solid grains or crystals after sediment accumulates and rocks form
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secondary porosity
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new pore space produced after a rock first forms, ie jointing and faulting
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permeability
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ability of a material to allow fluid to pass through an interconnected network of pores
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unconfined aquifer
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high porosity and permeability, above aquitard
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aquitards
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sediments and rocks that do not retard water easily and therefore retard the motion of water
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confined aquifer
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under aquitard
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The Mahomet Aquifer is an example of a . . .
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buried, gravel filled valley
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The High Plains Aquifer is an example of a . . .
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regional sandstone layer
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Water table
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boundary at which pore spaces begin to be filled with water
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Above the water table is the . . .
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unsaturated zone
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The water table follows the topography
True/False |
TRUE
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Hydraulic head
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built-in pressure from the water that is up above
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A water tower creates a synthetic . . .
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hydraulic head
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wells
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holes that people dig or drill to obtain water
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springs
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natural outlets from which groundwater flows
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cone of depression
why does it happen? |
water table becomes a downward pointing cone
happens when water is pumped out of a well too quickly or when one drills a well past the water table |
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artesian well
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flows out of the ground all by itself, from a confined aquifer
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potentiometric surface
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elevation to which an artesian well system would rise if unimpeded
in flowing artesian wells, surface lies above ground |
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springs form where . . .
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the water table comes out of the ground
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some things that can form springs
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- the presence of a permeable or impermeable layer
-fractures -faults |
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hot springs are caused by . . .
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magma under the ground, higher geothermal gradient, deep groundwater rising to the surface
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groundwater usage problems
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-lowered water table
-saltwater intrusion -subsidence -pollution plume develops |
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lowering the water table
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- when we extract groundwater from wells at a rate faster than it can be resupplied
-first, cone of depression, then broadening of depression -can also happen when surface water is diverted from a recharge area |
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saline intrusion
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- boundary between saline water and overlying freshwater rises above the base of the well
-happens when water is pumped out too quickly |
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subsidence
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-pore collapse because of extraction of water
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characteristics of Karst landscape
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-groundwater dissolving away rocks
-sinkholes-collapsed caves -caves -vanishing streams |
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How does water get in to streams?
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Rain and meltwater/precipitation
Water from land surface From groundwater |
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How does water get out of streams?
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Flows in to ocean
In to water table Evaporate |
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A permanent stream/lake is an
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outcropping of the water table
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Ephemeral streams
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do not flow all year
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How do streams erode the landscape?
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1. downward
2.headward 3. widens |
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dendritic discharge pattern
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like a decidious trees with limbs and branches flowing in to it
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radial discharge pattern
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forms on the surface of a cone-shaped mountain flow outward from the mountain peak, like spokes on a wheel
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rectangular discharge pattern
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happens at places where a radial grid fractures/joints and forms a rectangular network
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trellis discharge pattern
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flows out of either side of a trunk stream in a valley
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base level
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the lowest elevation a stream's channel floor can reach
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How does a waterfall form?
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-where the gradient of a stream becomes so steep that the water literally free falls down the stream bed
- a water fall is short lived/ transient |
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____form in hard rock
____ form in soft rock |
canyon
v-shaped valley |
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Changes in base level of streams can be caused by
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- sea level changes
-tectonics (land moves up) -canyons and valleys -terraces |
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alluvial fan
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gently sloping apron of sediment where a fast moving stream emerges from a mountain canyon in to an open plain
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braided stream
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choked by sediment, can't cut in to rock, commonly form where streams fill with sediment choked glacial meltwater
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