Deck 8: Subsidence and Soil Expansion and Contraction

Question 1

The land that Venice is built on has been subsiding for millions of years.What happened in the mid-1900s to increase the subsidence rate?

A) increased slippage along a dip-slip fault
B) increased use of heavier building materials
C) archeological excavations undermined the city
D) pumping of groundwater form under the city
E) draining of wetlands around the city

Answer 1

D

Question 2

How low do mean annual air temperatures need to be for permafrost to be continuous?

A) at least below 0 degrees Celsius
B) at least below -2 degrees Celsius
C) at least below -5 degrees Celsius
D) at least below -10 degrees Celsius
E) at least below -15 degrees Celsius

Answer 2

C

Question 3

During the formation of karst topography,what typically happens to the water table?

A) The water table rises.
B) The water table falls.
C) The water table intersects the surface.
D) The water table disappears.
E) The water table remains relatively constant.

Answer 3

B

Question 4

The populated Fraser River delta south of Vancouver,B.C.,is subsiding primarily because

A) dams upstream catch the sediments that otherwise would reach the delta.
B) groundwater pumped for agriculture is causing the ground surface to sink.
C) dykes built to protect human infrastructure keep new sediments off the delta.
D) slow slippage along the Cascadia subduction zone causes the delta to warp downward.
E) sea level rise is eroding the delta faster than replenishment occurs.

Question 5

The dissolution of limestone produces dissolved

A) calcium ions.
B) sodium ions.
C) chlorine ions.
D) sulfate ions.
E) potassium ions.

Question 6

Subsidence of the land surface on the flank of a volcano indicates that

A) the volcano is about to erupt.
B) the magma beneath the volcano has solidified underground.
C) the volcano has recently erupted.
D) the volcano has become dormant.
E) more hot magma has intruded into the magma chamber.

Question 7

How can scientists reconstruct past climate changes from caves?

A) by measuring the rates of cavern enlargement using carbon isotopes
B) by measuring isotopes of oxygen in cave formations such as stalactites
C) by measuring the amount of carbon dioxide in air exiting at cave openings
D) by examining and dating animal remains in cave deposits
E) by quantifying size and production rate of sinkholes above a cave system

Question 8

What is the most appropriate adjustment to subsidence hazards?

A) Construct detailed geologic maps of subsidence hazards.
B) Construct detailed subsurface maps using ground penetrating radar.
C) Avoid building in subsidence-prone regions.
D) Require full risk disclosure to potential property buyers.
E) Deny insurance coverage to those who live in hazardous areas.

Question 9

Approximately what percentage of the Earth's land surface is permafrost?

A) 1%
B) 2%
C) 5%
D) 10%
E) 20%

Question 10

Piping is most common in

A) mudstones.
B) limestone bedrock.
C) rock salt pockets.
D) silty/sandy sediments.
E) permafrost.

Question 11

How is most table salt produced?

A) evaporation of seawater
B) open-pit salt mines
C) mountaintop removal
D) solution mines
E) shaft and tunnel mines

Question 12

Why are springs in karst landscapes particularly vulnerable to contamination?

A) Natural sinkholes are commonly used as landfills.
B) Toxic metals dissolved out of limestone become concentrated in these springs.
C) Surface pollutants can easily enter and move through underground drainage systems.
D) Deep pumping of groundwater for agriculture draws pollutants from fertilizer into springs.
E) Spring water comes from stagnant underground pools where pollutants concentrate.

Question 13

Soils containing smectite clay minerals have a high potential for swelling and shrinking because

A) the relatively large, plate-shaped clay crystals pack together tightly.
B) the very small clay crystals have a large surface area to attract water molecules.
C) the clay-rich soils allow water to percolate through easily.
D) organic matter in the soils retains water during dry periods.
E) the soil particles break apart easily during freeze-thaw cycles.

Question 14

Which of the following types of bedrock is most associated with subsidence?

A) limestone
B) basalt
C) granite
D) mudstone
E) sandstone

Question 15

Approximately what percentage of the Earth's land surface is karst?

A) 1%
B) 2%
C) 5%
D) 10%
E) 20%

Question 16

Which of the following processes could cause subsidence the most quickly?

A) gypsum dissolution
B) permafrost thawing
C) clay-rich soils shrinking and swelling
D) earthquake
E) groundwater pumping

Question 17

Tower karst forms in

A) temperate rainy regions.
B) humid tropical regions.
C) dry warm regions.
D) mountainous rainy regions.
E) permafrost regions.

Question 18

Dissolution of what atmospheric gas causes rainwater to be slightly acidic?

A) oxygen
B) nitrogen
C) carbon dioxide
D) argon
E) helium

Question 19

If you were planning to build a house on permafrost,which of the following precautions would be prudent?

A) Dig a deep foundation into the permafrost.
B) Construct a basement.
C) Build directly on the ground and insulate your floor well.
D) Elevate your house above the ground.
E) Excavate to bedrock, even if it's tens of metres down.

Question 20

A possible mitigation strategy to avoid the collapse of old coal mine adits or tunnels is to fill them with sand to support the roof.This strategy was employed in old gold mines in Timmins,Ontario.What happened over time to make this strategy ineffective?

A) Pore water pressures within the sand increased and caused liquefaction subsurface.
B) Some of the sand washed away and no longer supported the tunnel roofs.
C) The sand settled and compacted, leaving voids into which the roofs collapsed.
D) The sand displaced subsurface water, raising the water table and flooding parts of the surface.
E) The sand allowed water to flow freely through pore spaces, dissolving more material from the mine walls.

Question 21

Which of the following causes subsidence?

A) dissolution of rock
B) eruption of magma
C) earthquakes
D) dehydration of sediment
E) all of the above

Question 22

Which areas are most prone to subsidence?

A) areas underlain by permafrost
B) swampy areas
C) areas underlain by limestone
D) river deltas
E) all of the above

Question 23

Which two cities have issues with subsidence?

A) New York and Vancouver
B) Venice and Vancouver
C) Mexico City and Tokyo
D) Los Angeles and San Francisco
E) London and New Orleans

Question 24

Tower karst

A) is the result of dissolution in warm tropical climates.
B) is common in Canada.
C) develops in granitic rocks.
D) is caused by alkaline groundwater.
E) occurs in volcanic areas.

Question 25

The term "loess" refers to

A) clay-rich lake sediments.
B) re-sedimented volcanic ash.
C) organic-rich mud rocks.
D) sandy stream deposits.
E) windblown silt deposits.

Question 26

Expansive soils expand and contract due to changes in

A) temperature.
B) mineral content.
C) water content.
D) erosion rate.
E) building designs.

Question 27

Which of the following is NOT a feature of karst systems?

A) solution valley
B) sinkhole
C) disappearing stream
D) bulging
E) caverns

Question 28

Limestone dissolution in a karst setting is due largely to the generation of this acid.

A) nitric acid
B) humic acid
C) carbonic acid
D) perchloric acid
E) bicarbonate acid

Question 29

Expansive soils

A) cause problems in areas of permafrost.
B) are a problem only in areas with pronounced wet and dry seasons.
C) are not affected by vegetation.
D) produce different ill-effects to ice-prone soils.
E) are found in areas of karst.

Question 30

The city of Venice,Italy has been subsiding (sinking)at a rate of

A) 10 cm/year.
B) 2 mm/year.
C) 100cm/year.
D) 15 mm/year.
E) 25 cm/year.

Question 31

What flood control method has been put in place to protect the city of Venice?

A) dykes
B) pumping of groundwater
C) sea walls
D) floodgates
E) none

Question 32

Groundwater mining

A) is the extraction of more groundwater than can be replenished by nature.
B) has led to permanent ground subsidence.
C) cannot be continued indefinitely.
D) is now eliminated in Texas and has decreased or eliminated subsidence.
E) all of the above.

Question 33

Subsidence in areas underlain by organic (swampy)soils is due in part to

A) a high water table.
B) bacterial decomposition of organic material to CO₂.
C) infusion of CO₂.
D) irrigation.
E) river flooding.

Question 34

What acid is a natural component of rain?

A) sulphuric
B) nitric
C) acetic
D) carbonic
E) hydrochloric

Question 35

Solution mining

A) is a term used for mining of renewable resources.
B) is no longer used.
C) does not lead to subsidence.
D) is only used for surface deposits.
E) is a method used to extract soluble minerals from the ground.

Question 36

Discontinuous permafrost occurs where the mean annual air temperature

A) is lower than -5°C.
B) is lower than 0°C.
C) lies between 0°C and 5°C.
D) lies between -5°C and 0°C.
E) is lower than -10°C.

Question 37

Why is New Orleans sinking?

A) It is built on soluble rocks.
B) Levees and dykes prevent the Mississippi from supplying new sediment to balance compaction.
C) The wetlands are disappearing.
D) Hurricanes are becoming stronger.
E) Modern buildings are too heavy and cause increased compaction.

Question 38

Troglobites

A) are a group of early humans who made their home in caves.
B) include all bats.
C) are plants that photosynthesize without light.
D) are organisms that have evolved to survive in the complete darkness of caves.
E) are a species of fish that have no eyes.

Question 39

To qualify as permafrost,sediment or rock must remain cemented with ice for

A) a minimum of two years.
B) at least six months.
C) the entire year.
D) five years.
E) the summer months.

Question 40

Draining wetlands

A) causes uplift and increases the risk of flooding.
B) causes subsidence and increases the risk of flooding.
C) causes subsidence but decreases the risk of flooding.
D) does not cause subsidence or uplift.
E) decreases the need for levees.

Question 41

In order to avoid melting permafrost,homes in permafrost area are elevated above ground.

Question 42

Thawing of permafrost in the Arctic is due primarily to

A) climate warming.
B) increased development and construction.
C) increased precipitation.
D) rising sea level.
E) subsidence.

Question 43

If you were to move to the southernmost shore of Hudson Bay,it's likely that you would encounter thermokarst.

Question 44

Sinkholes tens of metres in diameter can form in only a few minutes.

Question 45

Extracting oil from subsurface sandstone reservoirs can induce or accelerate subsidence.

Question 46

Karst formations are important sources of clean drinking water.

Question 47

Unique species have adapted to photosynthesize in the total darkness of caves in karst terrain.

Question 48

No metamorphic rocks are subject to dissolution.

Question 49

Flowstone consists of

A) clay-rich sediments that catastrophically fail and begin to flow.
B) limestone deposits on sides of cave walls.
C) sandy units, which act as aquifers and allow fluid movement.
D) porous limestone, which allows percolation of waters.
E) rock which is susceptible to subsidence.

Question 50

If a small lake forms in a sinkhole,the water is likely to fill up the sinkhole and overflow.

Question 51

The city of Venice is no longer sinking now that groundwater pumping was stopped in the 1970s.

Question 52

The floodgate system installed at Venice,Italy will prevent flooding for the foreseeable future.

Question 53

Expansive soils are a larger problem in southern Canada than in northern Canada.

Question 54

Deposits of calcium carbonate that grow from the ceiling of caverns are known as

A) stalagmites.
B) stalactites.
C) flowstone.
D) tower karst.
E) limestone.

Question 55

"Karst plain" describes a ground surface that is pockmarked with many sinkholes.

Question 56

When groundwater is pumped for irrigation,the water percolates through the surface and back into the water table,effectively refilling the reservoir,therefore no net subsidence occurs.

Question 57

In permafrost regions,the topmost portion of ground that undergoes thawing and freezing is the

A) transition zone.
B) thermokarst.
C) discontinuous layer.
D) frost zone.
E) active layer.

Question 58

Thin-bedded limestone rocks are more vulnerable to dissolution than thick-bedded limestone rocks.

Question 59

In the next great earthquake along the Cascadia subduction zone,the west coast of Vancouver Island is expected to subside suddenly.

Question 60

Structural damage due to soils shrinking and swelling is a larger problem in regions with pronounced wet and dry seasons than in regions where precipitation is more evenly distributed throughout the year.

Question 61

What is subsidence?

Question 62

Half of the Canadian Arctic is underlain by permafrost.

Question 63

Expansive soils contain the clay mineral smectite.

Question 64

What is flowstone?

Question 65

Subsidence accompanying underground mining activities is limited to soft rock formation,such as salt,potash,phosphate and coal.

Question 66

Why are rock salt and gypsum deposits commonly associated with subsidence?

Question 67

Construction of the Aswan dam hundreds of kilometres from the Nile delta has still led to subsidence in the delta.

Question 68

Millions of dollars in damage is caused each year by expansive soils.

Question 69

What pH conditions are needed for dissolution of limestone?

Question 70

Destructive subsidence and development of karst can result in favourable formations,which supply clean drinking water.

Question 71

Lakes in areas of karst commonly have no surface streams feeding them.

Question 72

How can water percolating through soil become more acidic?

Question 73

In warmer climates,discontinuous patches or thin layers of permanently frozen ground are included as permafrost.

Question 74

Volcanism can cause both uplift and subsidence: uplift in areas of deposition of new volcanic rocks,and subsidence over the empty magma chamber.

Question 75

A solution sinkhole occurs when an underground cavern collapses.

Question 76

Proper design and construction can minimize damage to structures sitting on expansive soils and sediments.

Question 77

Groundwater in karst areas is immune from pollution because the water flows into and out of the ground easily.

Question 78

In karst areas,natural discharges of groundwater at the surface are known as springs.

Question 79

What is the difference between stalactites and stalagmites?

Question 80

Lakes in karst areas can disappear overnight.