Deck 16: Groundwater

Question 1

A large cone of depression is least likely to develop when:

A) there is little precipitation in an area.
B) the aquifer has minimum permeability.
C) a large amount of water is removed from an aquifer.
D) recharge exceeds discharge.

Answer 1

D

Question 2

Banded draperies form when:

A) the partition between two adjacent caves erodes to a thin, curtain- like structure.
B) a series of columns becomes connected.
C) water from the cave ceiling washes over a section of a cave wall.
D) speleothm is deposited below a joint or crack in the cave ceiling.

Answer 2

D

Question 3

Which of the following statements concerning collapse sinkholes is NOT true?

A) Excessive withdrawal of groundwater by communities may initiate sinkhole formation.
B) They are usually more shallow than solution sinkholes, and their sides are more gently sloping.
C) A sinkhole may form where soil has filtered down into a cave, leaving overlying soil voids.
D) Excessive weight of wet soil may cause caverns to collapse, forming a sinkhole.

Answer 3

B

Question 4

Cave pearls have a round shape because:

A) erosion tends to remove any edges or corners.
B) the crystalline structure of travertine is spherical.
C) they form in agitated pools that keep the pearl in motion.
D) they develop on smooth, round sand grains.

Question 5

The first water to move through a dry soil:

A) evaporates into the air trapped within soil pore spaces.
B) evaporates back into the atmosphere.
C) infiltrates downward into the zone of saturation.
D) becomes attached to the surfaces of clay minerals or is used by plants.

Question 6

Groundwater would flow the fastest between two points if:

A) the hydraulic gradient is high and the hydraulic conductivity is low.
B) the hydraulic gradient and the hydraulic conductivity are both low.
C) the hydraulic gradient and the hydraulic conductivity are both high.
D) the hydraulic gradient is low and the hydraulic conductivity is high.

Question 7

The greatest infiltration of surface waters would be on:

A) gentle slopes.
B) cliff faces.
C) steep slopes.
D) steep, vegetated slopes.

Question 8

The capillary fringe is located:

A) below the water table and is part of the zone of saturation.
B) just below the surface of the ground and is part of the zone of aeration.
C) between the zone of aeration and the zone of saturation.
D) just above the water table and is part of the zone of aeration.

Question 9

Natural bridges form from:

A) accumulations of sediment across sinkhole lakes.
B) spans of insoluble rock that connect sinkholes.
C) uncollapsed material between expanded and coalesced sinkholes.
D) interconnections of large speleothems.

Question 10

Which of the following methods of enhanced recharge is used by Denver and New York City?

A) Interbasin transfer.
B) Intrastate transfer.
C) Injecting lake water into the ground.
D) Building recharge basins.

Question 11

A prominent surface feature of karst land would be:

A) braided streams.
B) disappearing streams.
C) meandering streams.
D) rectangular drainage patterns.

Question 12

The desalinization of seawater is an uncommon way to relieve water shortages even in areas near the ocean because:

A) desalinization technology is still in its infant stages.
B) it is usually not economically feasible.
C) sufficient quantities of water cannot be produced.
D) it would upset the global hydrologic cycle.

Question 13

Cross sections of speleothems reveal an ancient ice age because:

A) speleothems do not grow when a cave is overlain by a sheet of ice.
B) speleothems produce thicker concentric layers when the cave is affected by an ice age.
C) darker layers within a speleothem represent periods of colder climate.
D) some of the concentric layers within a speleothem contain pockets caused by ice formation.

Question 14

When water is withdrawn from a well, a cone of depression is created in which:

A) the water table in the vicinity of the well is temporarily lowered.
B) the groundwater potential in the vicinity of the well is lowered.
C) the soil within the aquifer presses inward toward the well.
D) the land surface in the vicinity of the well subsides.

Question 15

Which of the following statements about karst in desert regions is true?

A) High temperatures in deserts promote fracturing in limestone.
B) Thick desert soils promote limestone solution.
C) Karst features in deserts indicate former times of greater precipitation.
D) High temperatures in deserts promote limestone solution.

Question 16

The instrument water witches use to locate underground water is called a:

A) shovel.
B) forked stick.
C) long pipe.
D) well driller.

Question 17

The rate at which groundwater flows over a long distance can be measured with which of the following radioactive isotopes?

A) Potassium.
B) Carbon- 14.
C) Uranium.
D) Rubidium.

Question 18

A water table's configuration is usually:

A) random and unpredictable.
B) parallel to the topography, with highs under hills and lows in valleys.
C) opposite to the topography, with highs in valleys and lows under hills.
D) flat, because water seeks its own level.

Question 19

Grading steep slopes can enhance groundwater recharge because such a measure:

A) reduces the runoff from precipitation.
B) reduces the depth of the water table.
C) removes impermeable materials.
D) reduces the hydraulic gradient of the groundwater.

Question 20

Groundwater sometimes flows upward against gravity because:

A) the pressure from overlying water and surrounding rocks forces groundwater to flow in specific directions.
B) groundwater is not governed by the same physical laws as surface water.
C) groundwater is pulled by the flow of overlying surface water.
D) oversaturation occurs within the zone of saturation.

Question 21

All of the following statements about disappearing streams are true EXCEPT:

A) they seldom meander.
B) they present serious flooding problems when sinkholes become plugged.
C) they drain completely into sinkholes.
D) they may return to the surface as natural springs.

Question 22

The potentiometric surface of an artesian aquifer is:

A) the boundary between the artesian aquifer and an overlying confining layer.
B) the difference in elevation between the area of recharge and the area of discharge.
C) the level to which the water in the area of discharge would rise in the absence of friction.
D) the difference in groundwater potential between water in the area of discharge and water in the area of recharge.

Question 23

The average rate of limestone dissolution in England is measured in:

A) decameters per 100 years.
B) centimeters per 100 years.
C) meters per 100 years.
D) millimeters per 100 years.

Question 24

Caves are formed by what geological process?

A) Surface stream deposition.
B) Subsurface stream erosion.
C) Surface stream erosion.
D) Subsurface dissolution.

Question 25

Which of the following statements about stalactites is NOT true?

A) In mature stages, they resemble large icicles and grow when water drips along the outside.
B) They are composed of the rock travertine and are hollow inside.
C) In their early stages, they are tube- like and grow when water drips through the inside and deposits calcium carbonate at the end.
D) They form as groundwater seeps into the roof of a cave and evaporates or releases carbon dioxide.

Question 26

Caves found in New England and parts of eastern Canada tend to be relatively small and less extensive primarily because:

A) the type of limestone found there is unusually resistant to dissolution.
B) the bedrock is crystalline and contains little limestone.
C) the groundwater is less acidic.
D) the major source of precipitation is snow.

Question 27

Which of the following statements about limestone is NOT true?

A) Calcium bicarbonate is produced as a result of the dissolution of limestone by carbonic acid.
B) The most soluble component of limestone is the mineral calcite.
C) Limestone dissolves most readily in pure water.
D) Limestone may contain as little as 50% calcite.

Question 28

Which of the following statements about water that contains dissolved calcium bicarbonate is NOT true?

A) It is considered hard water and may leave calcium carbonate deposits in plumbing pipes.
B) It is responsible for the dissolution of limestone.
C) It can be carried to the sea where marine organisms use it for building shells.
D) It may infiltrate through unconsolidated sediments and deposit calcite as a cementing agent.

Question 29

The radioactive wastes at Yucca Mountain would be stored:

A) 240 meters above the surface, in a limestone vault.
B) 300 meters beneath the surface, in welded tuffs.
C) 40 meters beneath the surface, in welded tuffs.
D) at the surface in a limestone vault.

Question 30

A perched water table is a water table:

A) that lies at an extremely high angle.
B) found on top of a local impermeable layer lying above the zone of saturation.
C) that is found high in the mountains.
D) where one highly permeable rock layer overlies another highly permeable rock layer, and both are dependent on the same recharge source.

Question 31

Initial cave formation takes place:

A) at the land surface.
B) in the zone of aeration.
C) in the zone of saturation.
D) in the capillary fringe.

Question 32

Approximately what percentage of the United States is karst land?

A) 35%.
B) 25%.
C) 15%.
D) 45%.

Question 33

Withdrawal of groundwater has produced the most severe subsidence in:

A) Las Vegas.
B) Mexico City.
C) New Orleans.
D) Central California.

Question 34

Which of the following statements about thermal springs is NOT true?

A) Most are heated either by contact with hot igneous rocks or by water circulating within regions heated by the Earth's geothermal heat flow.
B) Mineral deposits called sinter form where thermal spring water reaches the surface and evaporates.
C) A thermal spring may also be an artesian spring.
D) A thermal spring is one in which the water temperature is within a few degrees of the boiling point.

Question 35

The method used to conclusively identify the best place to drill a well is to:

A) employ the services of dowsers, because they have been proven completely reliable.
B) survey an area's vegetation because certain plant species indicate specific depths of the water table.
C) locate sources of surface water because such sources intersect the water table.
D) drill test wells, because they show the depth of the water table at particular places.

Question 36

An unconfined aquifer is one that:

A) has no impermeable layer beneath it.
B) is unbounded laterally by geological obstacles.
C) has no impermeable layer either above or beneath it.
D) has no overlying impermeable layer.

Question 37

Open- air spaces within the cave cause downward percolating groundwater to do all of the following EXCEPT:

A) lose carbon dioxide, causing carbonic acid to convert to water and carbon dioxide.
B) carbon dioxide loss causes calcium carbonate to precipitate from solution.
C) evaporate, saturating the remaining water with calcium bicarbonate.
D) dissolve more of the limestone present.

Question 38

Saltwater intrusion is most serious in which region?

A) On peninsulas.
B) In heavily populated coastal areas.
C) On islands.
D) All of the above.

Question 39

Groundwater represents what percentage of the world's water?

A) 6%.
B) 60%.
C) 16%.
D) 0.6%.

Question 40

Groundwater can clean itself of all of the following contaminants EXCEPT:

A) sewage bacteria.
B) dissolved chemical pollutants.
C) larger viruses.
D) suspended solids.

Question 41

What causes the dissolution of limestone?

Question 42

Discuss the laws governing ownership of groundwater in the United States.

Question 43

How do collapse sinkholes form?

Question 44

Primary porosity would probably be the greatest in which of the following?

A) Well- sorted, coarse- grained sediment.
B) Fine, clayey mud.
C) Well- cemented, sedimentary rock.
D) Angular- grained, sedimentary rock.

Question 45

Explain how geologists trace water from disappearing streams to specific springs.

Question 46

Explain why groundwater is an important resource.

Question 47

It is especially important to protect groundwater within cave systems from contamination because:

A) water is not filtered, and there is not enough time for microorganisms to consume contaminants.
B) karst groundwater often seeps upward into the soil and contaminates agricultural crops.
C) the chemical constituents of limestone tend to enhance contaminants rather than degrade them.
D) pollutants accumulate so rapidly that natural cleaning mechanisms are overloaded.

Question 48

Describe the methods that are used to find groundwater sources.

Question 49

Describe the formation and growth of helictites, cave pearls, and cave popcorn.

Question 50

What methods are used to estimate the rate of limestone dissolution?

Question 51

What is the relationship between local topography and bodies of surface water and the level of the water table?

Question 52

Discuss the flow rate of groundwater in terms of groundwater potential and Darcy's findings.

Question 53

All of the following materials encourage infiltration EXCEPT:

A) loose soils and gravels.
B) coarse sandstone.
C) porous, unconsolidated clays.
D) fractured or jointed bedrock.