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GEOL-1403 > Lesson 14: Ground Water > Flashcards

Lesson 14: Ground Water Flashcards

1
Q

What is the main use of groundwater in the U.S.?

A

Irrigation (Agriculture)

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2
Q

Where does the groundwater stay in the rock?

A

in open spaces (pores) within rocks and unconsolidated sediments.

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3
Q

What is porosity?

A

The percentage of open pore space within an unconsolidated sediment/rock

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4
Q

What is permeability?

A

How connected the pore spaces are to one another; controlled solely by pore geometry

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5
Q

Compare porosity and permeability

A

Porosity: determines how much groundwater can be stored
Permeability: determines how well water can flow from one pore to another

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6
Q

Define vadose zone.

A

The unsaturated zone above the zone of saturation; includes both air and water

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7
Q

Define saturated zone.

A

The zone of saturation where all pore spaces are completely filled with water; water in this zone is groundwater

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8
Q

Define water table.

A

The upper limit of the zone of saturation.

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9
Q

Compare losing and gaining streams.

A

Losing Streams: streams lose water to the groundwater system by outflow through the streambed; the water table is lower than the level of a stream

Gaining Streams: streams gain water from the inflow of groundwater through the streambed; the water table is higher than the level of the stream.

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10
Q

What is an Aquitard?

A

an impermeable layer that hinders/prevents groundwater movement

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11
Q

What is an Aquifer?

A

A porous and permeable zone that is saturated with water that is recharged as surface water seeps downward

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12
Q

What types of rocks make an aquitard?

A

Shale/mudrock and clay

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13
Q

What types of rock make an Aquifer?

A

Sand and glacial till

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14
Q

What is a confined aquifer?

A

An aquifer that has permeable rock units enclosed within impermeable rock units; recharged in highlands where permeable rocks are exposed

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15
Q

What is an unconfined aquifer?

A

An aquifer that is connected to the surface by open pore spaces through which it can be recharged

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16
Q

What is a perched aquifer?

A

When there is a limited aquitard; it may be a good source of water during some parts of the year, but is very thin and small, and can be depleted easily.

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17
Q

What is drawdown?

A

As water is withdrawn from a well, the surrounding water table is lowered.

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18
Q

Where do drawdowns form?

A

at the water table

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19
Q

What is a cone of depression?

A

the lowering effect on the water table

20
Q

Where does a cone of depression form?

A

at the base of a well stem

21
Q

What are artesian wells?

A

a system where groundwater under pressure rises above the level of the aquifer

22
Q

Where do artesian wells form?

A

in a confined and inclined aquifer

23
Q

What is the main corrosive component in groundwater?

A

Carbonic acid

24
Q

How is Carlsbad Cavern in New Mexico different than most other caverns?

A

they formed due to reactions with sulfuric acid-bearing water

25
Q

What are the 5 common rocks that easily dissolve?

A
  1. Limestone
  2. Dolostone
  3. Halite/rock salt
  4. Gypsum/Rock Gypsum
  5. Marble
26
Q

What is Karst topography?

A

a landscape that has been shaped mainly by the dissolving power of groundwater

27
Q

What are the different karst landscapes?

A
  1. Sinkholes
  2. Caves/caverns
  3. Tower karst
  4. Disappearing streams
  5. Springs
28
Q

How do sinkholes form? (3) types

A
  1. Dissolution: Rainfall and surface water percolate through joints of a limestone, dissolved carbonate rock is carried away from the surface, and a depression gradually forms
  2. Cover-Subsidence: Granular sediments spall into secondary openings in the underlying rocks, and a column of overlying sediments settles into the vacated spaces, forming a noticeable depression in the land surface
  3. Cover-Collapse: Sediments spall into a cavity as spalling continues the cohesive covering sediments form a structural arch. The cavity migrates up by progressive roof collapse and eventually branches creating a sudden and dramatic sinkhole
29
Q

How do caves form?

A

By chemical dissolution resulting from circulating groundwater

30
Q

How do tower karsts form?

A

limestone rises above the surrounding landscape in highly eroded karst regions

31
Q

What are disappearing streams?

A

streams that disappear into cave openings that flow directly into the groundwater system.

32
Q

What are springs?

A

Groundwater that is becoming surface water

33
Q

What is speleothem?

A

A general name for dripstone features

34
Q

How do stalactites differ from stalagmites?

A

Stalactites hang from the ceiling
Stalagmites form from the ground

35
Q

___ accounts for the largest percentage of groundwater usage in the US

A

Irrigation

36
Q

Porosity may be defined as:

A

the percentage of pore spaces in a rock/sediment

37
Q

_____ refers to how connected pore spaces are to one another.

A

Permeability

38
Q

______ are characteristics found in all good aquifers.

A

High porosity and high permeability

39
Q

The unsaturated (vadose) zone…

A

lies above the water table

40
Q

Highly impermeable layers such as compacted clay/shale are known as _____.

A

Aquitards.

41
Q

The lowering effect on the water table at the base of the well stem is called a ______.

A

cone of depression

42
Q

In an ______ system groundwater under pressure rises above the level of the aquifer.

A

artesian

43
Q

Does permeability depend on fluid properties?

A

No

44
Q

Which of the following sedimentary rocks is NOT easily dissolved?
a. limestone
b. sandstone
c. dolostone
d. Halite

A

b. sandstone

45
Q

____ topography is a landscape that has been shaped mainly by the dissolving power of groundwater.

A

Karst

GEOL-1403 (26 decks)

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