Reading Assessment Chapter 8

What is karst topography?

A ragged surface characterized by sinkholes and underground caves

What is subsidence?

A sinking of the ground surface

In terms of soil development, what factor is most important in determining whether a soil is weakly, moderately, or well-developed?

Age

What is the definition of soil according to a soil scientist?

Any solid earth material that has been altered by physical, chemical, and organic processes so that it can support rooted plants

What causes volume change in expansive soil?

Changes in the water content

What is the most important soil particle that characterizes expansive soils?

Clay minerals

Which of the following is the correct order of soil grain size from smallest to largest?

Clay, silt, sand, gravel

What is the main difference between collapse sinkholes and solutional sinkholes?

Collapse sinkholes involve the surface rock and soil falling into an underground cave whereas solutional sinkholes form by downward dissolution from the bedrock surface.

Which of the following does NOT cause ground subsidence?

Creation of permanently frozen ground where no thawing ever occurs

Which of the following is the best match between climate and soil hazard?

D. Expansive soils with distinct wet and dry seasons

Which of the following is NOT usually caused by land subsidence or soil volume change?

Disease

Which of the following is NOT a normal definition of soil erosion?

Dissolution of flowing acidic groundwater to produce a large underground opening

What are two causes of the subsidence of New Orleans?

Draining of organic-rich soil and loss of supply of fine sediments by rivers

Caves form in places where giant bubbles were present in the lava that formed the Earth's crust.

False

Haiti faces a major problem of soil erosion because it has been growing corn without applying any fertilizer for centuries and that has depleted the soil of its nutrients.

False

In the U.S. subsidence and expansion and contraction of the soil are natural hazards that are well publicized and get considerable media coverage.

False

Karst landscapes are very dangerous to humans and all measures should be taken to prevent them.

False

Organic soils cause large amounts of damage in the U.S. because they swell when wet and shrink when dry.

False

Sinkholes usually form when the ground becomes wet and things sink into them after a big rainstorm.

False

Subsidence and soil volume changes are rare and don't cause very much damage in the U.S. due to advanced engineering methods.

False

The Mississippi Delta has experienced major subsidence over the past fifty years and that has resulted in a huge increase in the amount of wetlands.

False

The main societal impact of soil erosion is that the eroded soil ends up filling our water reservoirs and diminishes our drinking water supply.

False

The soil classification scheme created by soil scientists is based solely on the abundance of sand vs. clay.

False

There have not been too many problems due to land subsidence in the United States.

False

There is little that can be done to prevent damage from expansive soils.

False

Which of the following statements describes subsidence at the central (San Joaquin) valley of California?

Gradual subsidence occurred over several decades due to the withdrawal of groundwater mainly for irrigation purposes.

Which of the following is NOT a readily dissolvable rock?

Granite

What is groundwater mining?

Groundwater is pumped from the ground faster than it is replenished.

Which of the following is NOT a way that climate change can contribute to the subsidence problem?

Groundwater will warm, causing a large increase in dissolved limestone and sinkhole formation.

Where does the majority of soil originate from?

It comes from weathered rock.

Which of the following states has the greatest percentage of karst topography?

Kentucky

Which of the following does NOT usually affect the development of most soil?

Landslides

Which of the following is NOT an indication that there are expansive soils in an area?

Large circular holes with broken pieces of rock at the bottom.

Which of the following is the correct link between the soil and its horizon classification?

O is organic material.

How does pumping oil contribute to land subsidence?

Oil is removed, which removes the buoyant support it provided for the earth material, causing it to be more compacted.

If you were digging down into a soil, which horizon would you hit last?

R

How good of an indicator is soil color in categorizing the soil horizon?

Reasonably good. Sometimes color can be misleading, but usually it can give you a good idea.

Which of the following statements about sinkholes is FALSE?

Sinkholes are usually found in remote and swampy areas.

Which of the following is NOT a Natural Service Function of subsidence?

Sinkholes can be used for landfills.

How are sinkholes related to water pollution?

Sinkholes provide a quick route for polluted surface water to contaminate groundwater.

If you were in a very cold climate and looking out at an area with many sinkholes and rough terrain, what would you most likely be looking at?

Thermokarst

Areas with extensive Limestone formations near the surface are particularly vulnerable to sinkholes and caves.

True

Before building structures in karst regions, it can be useful to use ground penetrating radar to examine the subsurface geology.

True

Humans have contributed to the thawing of permafrost through poor building practices.

True

In areas undergoing subsidence due to the overpumping of groundwater, flooding can be a major problem.

True

Karst topography is a common type of landscape seen in many areas of the United States.

True

Salt mines can be places for land subsidence because salt can be dissolved in water, leaving behind cavities for water to pool.

True

Sinkhole formation is influenced by dramatic changes in the water table level that happen during wet and dry seasons.

True

Sinkholes and caves involve extensive dissolution of rocks due to changing levels of groundwater.

True

The water content of a soil can be important in determining engineering properties such as the strength of a soil and its potential to shrink and swell.

True

Weathering is the physical and chemical breakdown of rocks into smaller pieces and is involved in soil development.

True

How does land subsidence contribute to water pollution?

Using sinkholes as landfills can cause pollutants to seep into groundwater.

In a region susceptible to sinkhole formation, the most likely times for collapse will be

When groundwater levels are low.