Natural hazards and disasters 4th edition hyndman test bank

Chapter 9

SINKHOLES, LAND SUBSIDENCE, AND SWELLING SOILS

MULTIPLE-CHOICE QUESTIONS

1. What causes sinkhole collapse? Where is the cavity that it collapses into, and how does that cavity form?

a. A limestone cavern dissolves out with acid rain; a sinkhole forms when its roof collapses.

b. Soil above a limestone cavern percolates down into the cavern, leaving a soil cavity above. That cavity may collapse to form a sinkhole.

c. An underground river erodes a wide area; a sinkhole forms if its roof collapses.

d. The roof of a gold or copper mine collapses to form a sinkhole.

e. Families of moles or gophers dig large underground chambers that can collapse to form sinkholes.

ANSWER: b

2. What causes caverns in limestone?

a. Hard grains of quartz sand carried in underground streams erode the soft limestone.

b. They form when rocks above collapse into the limestone.

c. Limestone readily dissolves in seawater, so the caverns formed originally at sea level.

d. Groundwater in limestone is somewhat caustic, so over many years, it dissolves limestone.

e. Rainwater dissolves carbon dioxide to make weak carbonic acid that dissolves limestone.

ANSWER: e

3. Where in North America are sinkholes most prevalent and why?

a. in Michigan, because outcrops of limestone are widespread and it is surrounded by the Great Lakes

b. in Washington state, because of all of the rain west of the Cascades

c. in metamorphic rocks of the Canadian Shield, because of all of the lakes

d. in Florida, because it is almost all limestone and has abundant groundwater

e. in Colorado, because layers of sedimentary rocks under the Great Plains bend up to the surface there

ANSWER: d [FIGURE 9-6]

4. What is karst and how does it form?

a. Karst is the ragged surface dissolved on the surface of limestone bedrock formerly buried under soil.

b. Karst is windblown dust deposited in areas of dune-like hills.

c. Karst is the deposit of calcium carbonate that precipitates on rocks in soil when groundwater evaporates.

d. Karst is the cold wind that blows off the North Atlantic Ocean at times in late fall.

e. Karst is the product of reaction between acid rain and limestone in the ground.

ANSWER: a

5. What are the main characteristics of soil above a limestone cavern that leads to the formation of a cover collapse sinkhole?

a. thin enough that it can trickle through limestone cracks into a cavern below

b. sandy and loose enough that it can trickle down into cracks in limestone

c. coarse-enough grains that surface water can percolate down into cracks above a limestone cavern

d. fairly well cemented so it can maintain the roof of a cavern

e. thick, clay-rich, and cohesive enough to develop a large cavern before it collapses

ANSWER: e

6. What weather conditions are most likely to foster the formation of sinkholes?

a. dry weather, because that dehydrates the soil, causing shrinkage and collapse

b. freezing weather, because freezing water expands, causing stresses that force fractures apart to collapse

c. dry weather, because that lowers the water table so the cavern roofs are not supported and may collapse

d. wet weather, because there is ample water to dissolve out caverns

e. wet weather, because the pressure of water in a cavern causes stress that can weaken and collapse the roof

ANSWER: c

7. Other than limestone, what other types of rocks are soluble and can form cavities that collapse?

a. salt and shale

b. shale and bauxite

c. salt and gypsum

d. kaolinite and smectite

e. smectite and gypsum

ANSWER: c

8. Which of the following areas has NOT seen major subsidence from groundwater withdrawal?

a. San Joaquin Valley of California

b. Las Vegas area

c. Houston area, Texas

d. Charleston, South Carolina

e. Venice, Italy

ANSWER: d [Table 9-1]

9. What causes swelling soils to swell?

a. When they get wet, water enters the clay mineral structure to cause swelling.

b. The presence of abundant kaolinite clay takes water in between its layers

c. When water in clay-rich soil freezes, the soil swells.

d. When an earthquake shakes wet soil, more water can get between the grains to cause swelling.

e. Landsliding of a mass relieves pressure on soil, permitting it to expand.

ANSWER: a

10. Which of the following does NOT lead to formation of sinkholes?

a. strong pumping of groundwater for crop irrigation in dry weather

b. pumping groundwater for spraying on crops to prevent freezing

c. construction of a heavy building over a limestone cavern

d. pumping waste fluids into the ground for disposal

e. drilling for groundwater

ANSWER: d

11. Which is NOT a method for recognizing the presence of swelling soils?

a. They are extremely slippery when wet.

b. They form a popcorn-like surface when dried out.

c. They stick like gum to the bottom of your shoes when wet.

d. Since they deform elastically, the ground feels spongy or bouncy underfoot.

e. They deform concrete foundations and walls.

ANSWER: d

12. A roof made of what kind of material collapses to form a cover subsidence sinkhole?

a. sandy and permeable sediment

b. evaporate deposits of salt and gypsum

c. solid limestone with a few fractures

d. porous limestone with lots of fractures

e. swelling soil

ANSWER: a

13. What is in water in the ground that helps it dissolve limestone?

a. nitric acid from nitrogen in the air combining with rainwater

b. carbonic acid formed from carbon dioxide in air combining with rainwater

c. nothing pure water has nothing in it, so it can dissolve more

d. oxygen the reactivity of oxygen oxidizes the calcium of limestone

e. sand the grains are much harder than limestone, making it more abrasive

ANSWER: b

14. How would you recognize a karst landscape?

a. Karst forms very rough deposits of calcium carbonate on various kinds of rock outcrops.

b. Karst forms a rather smooth, flat surface on limestone because of extensive solution by acid rain.

c. Karst has an extremely ragged surface dissolved on the surface of limestone bedrock.

d. Karst forms dune-like rounded hills of windblown dust.

e. Karst is the smooth surface formed on soft shales when salty sea spray reacts with them.

ANSWER: c

15. Why does Venice, Italy, have canals for gondolas and boats instead of normal streets for cars?

a. It was built on soft muds of a lagoon, and the heavy buildings settled into the mud.

b. The smectite soils in muds under it lead to lateral spreading and subsidence under the load of buildings.

c. The low ground next to the lagoon was a difficult place to provide a good road foundation.

d. Since the city was built about 1,600 years ago, the sea level has risen.

e. Extraction of groundwater below the city caused subsidence of the city below sea level.

ANSWER: e

16. Why are there so many small lakes and springs in western Florida?

a. Since the water table is essentially at the surface, any low area is filled with water.

b. Limestone caverns and sinkholes filled with water because of the high water table.

c. Groundwater rising through the limestone bedrock dissolves it as it reaches acid rain at the surface.

d. Many of them are old limestone quarries, abundant there because of cheap transportation near the Gulf.

e. A swarm of asteroids peppered the area a few thousand years ago; the holes have since filled with water.

ANSWER: b

17. Under what weather conditions are sinkholes most likely to form?

a. low pressure under the eye of a hurricane

b. especially dry season

c. especially wet season

d. El Niño

e. freezing weather

ANSWER: b

18. In the United States, sinkholes, subsidence, and swelling soils cause total dollar damage at which of the following levels?

a. more than earthquakes and volcanoes

b. more than hurricanes but less than floods

c. more than forest fires but less than floods

d. more than floods but less than landslides

e. less than hurricanes, floods, or landslides

ANSWER: a

19. Caves and caverns most commonly develop in:

a. granite

b. sandstone.

c. shale.

d. limestone.

e. schist.

ANSWER: d

20. Which of the following statements about sinkhole formation is incorrect?

a. Cover collapse is a way that a sinkhole can form.

b. Permafrost thaw is a way that a sinkhole can form.

c. Large caverns generally form in limestone just below the water table.

d. Cover subsidence is a way that a sinkhole can form

e. Sinkhole formation depends on the presence of soluble sedimentary rocks like limestone.

ANSWER: b

SHORT ANSWER QUESTIONS

1. What agricultural behavior is likely to lead to formation of more sinkholes?

ANSWER: Aggressive pumping of groundwater for crop irrigation or spraying on crops to prevent freezing. In both cases, pumping lowers the water table, removing roof support in caverns.

2. What aspects of construction can lead to the formation of sinkholes? Why?

ANSWER: Drilling of water wells or foundation test holes. A well-drilling truck can load the

top of a cavity to cause collapse. Drilling a hole in the top of a cavern can weaken the roof and cause collapse.

3. What material causes swelling soils?

ANSWER: Smectite, the swelling clay

4. How can you recognize the presence of swelling soils?

ANSWER: They are extremely slippery when wet; they form a popcorn-like surface when dried out.

5. What is bad about swelling soils?

ANSWER: Swelling deforms and cracks foundations, chimneys, walls, driveways, and roads; roads are extremely slippery when wet; landslides are more common.

6. What type of ground settling process is common in high latitudes?

ANSWER: Thawing of permafrost.

7. What is in water in the ground that helps it dissolve limestone? Where does that substance come from?

ANSWER: Carbonic acid; it forms from carbon dioxide in the air combining with rainwater

8. Name three of the eight states with the largest areas of ground subsidence, including sinkholes.

ANSWER: Florida, Georgia, Texas, New Mexico, Kentucky, Tennessee, Virginia, and Missouri [Figure 9-6]

9. What are two main mechanisms of ground subsidence?

ANSWER: Sinkholes, extraction of water or other fluids from sediments, and drainage of peat or other organic soils.

10. What specific area of the western United States is noted for almost 9 meters of subsidence due to agriculture? Specifically what caused the subsidence?

ANSWER: The San Joaquin Valley (Great Valley of California); subsidence caused by extraction of groundwater for agriculture. [Table 9-1]

CRITICAL THINKING ESSAY QUESTIONS

1. Your friend just got back from vacation and wants to know if you can help him understand why the place he visited looked so weird. He describes the landscape as being uneven, with lots of depressions, and some ragged parts. What type of landscape is this? How does this type of landscape form? If your friend was on vacation in the United States, where are some of the places he could have been?

ANSWER: Karst; Mammoth Cave National Park in Kentucky, Florida, southwestern Missouri, southeastern states, the Appalachians, or western Texas

2. Venice, Italy, is noted for numerous water canals instead of paved streets for cars. Why doesn’t it have many typical streets? Explain briefly.

ANSWER: Extraction of groundwater under the city caused subsidence and sinking of the city below sea level.

3. What causes permafrost thaw? What are several problems associated with it? What is one way to overcome permafrost thaw?

ANSWER: Permafrost thaw occurs when increased atmospheric temperature warms the ground surface, causing water to melt and settling to occur as water in the previously supported pore spaces in between grains flows out; permafrost thaw causes landslides, upsets foundations of buildings and roadways, and promotes melting of Arctic sea ice; installing thermosiphons into the Trans-Alaska Pipeline, building strategies, and when building roads, covering the permafrost with crushed stone

4. In the case of Mexico City, Mexico, land subsidence due to unsustainable groundwater pumping caused many problems because the area is highly populated. Discuss two of these problems.

ANSWER: Buildings tilt; water lines crack or break, causing huge losses of potable water; sewer lines are damaged, causing sewage and contaminants to infiltrate the aquifer below; 24-hour pumping is needed to prevent summer rains from flooding the city; sometimes, water supplies are shut down to conserve them

5. Discuss the four causes of land subsidence described in the text and one case study of each cause.

ANSWER: Mining groundwater and petroleum (San Jose, Houston, or Wilmington/Long Beach); drainage of organic soils (San Joaquin Valley, Florida Everglades, Mississippi River delta, or the Netherlands); drying of clays (Leaning Tower of Pisa or Ottawa–St. Lawrence River lowland); thaw and ground settling (Trans-Alaska Pipeline).

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dear, dear lord, that most generous friend, how good he has been to us all! I do love him, though I never have seen him. Oh, how I wish that I could do something, were it ever so little, to show him how very, very thankful I am."

The desire to show her gratitude in something more than words had taken strong hold of the loving heart of the child. Grace sat for more than an hour thinking and thinking what she—even she—could do for the merciful lord of the manor

"I should like to make him a nosegay of all the best flowers in my garden; I would strip off every blossom," said the child to herself "But flowers die so soon; and then the gardens round the Castle hold flowers a hundred times prettier than mine. I am afraid that the rich master would scarcely look at my nosegay. I should like to work from morning till night to make something fit to give him; but I am little, and cannot work well;—I do not see what I could make. But oh, I must find some way of letting the generous lord know how grateful I am for his goodness!"

In the midst of her perplexity, the eye of little Grace rested on her white dove. This was her greatest treasure, the one thing which she valued beyond all others.

"I wonder if the great lord would accept Heartslove," murmured the child. "I should not indeed like to lose my dear dove; but I have nothing else worth offering to the friend who has saved my father. The bird is my own, my very own; I may give it to any one that I please; and shall I grudge it to him to whom we owe everything that we have?"

There was a little struggle in the mind of the child, but it ended in her resolving to offer her pet bird to the lord of the manor.

Full of her grateful design, Grace put her dove into a little woven basket, with open work on the lid, and lined the basket with moss, that her favourite might take no harm by the way. Grace then wont and asked her father to carry her dove to the great and good lord at the Castle.

"I am far too busy to do any such thing," said Seele, who was just about starting off to make a new purchase of cows for his dairy, with the money advanced by his kind benefactor. "Go you up to the Castle, child, and take your present yourself."

Grace was afraid to go up to the Castle, though she knew the road to it perfectly well, for she had often gathered acorns under the great oaks of the park while the lord of the manor had been absent. But though feeling timid and shy, Grace was too anxious to offer her humble gift to be easily put aside from her purpose.

"I will just venture as far as the outer gate," she said to herself, "and give the basket to one of the servants, and beg him kindly to take it to the generous lord."

So Grace put on her little bonnet and cloak. In vain she tried to get one of her brothers or sisters to go with her—they too said that they were too busy: not one seemed to think that it was in the least needful to show gratitude, or even to feel it.

So Grace set out quite alone. Ofttimes on her way, she raised the lid of the basket a little to take a last peep of her pet.

"I shall miss you, but I do not grudge you, my little beauty!" said the child. "I am sure that so kind a lord will be gentle and good to my bird. He will not despise or hurt you; and when he hears your soft note in the morning, he will know that you are cooing the thanks of a little child for what he has done for us all."

But when Grace reached the large gate beside which hung the great iron bell, she had hardly courage to ring it. After all, thought she, might not so grand a nobleman think it presuming in her to come even to offer a gift? Was the bird, though it was her all, worthy to be placed before him? Should she not rather carry Heartslove back to her home?

While Grace stood hesitating and doubting, with her small hand raised to the bell handle, which she did not venture to pull, a man of a noble appearance, who was walking within the Castle grounds, came up to the gate.

"What do you want, little girl?" he inquired in a tone so gentle, that even timid Grace was not afraid to reply to the question.

"O sir, I am the child of Ernst Seele," she replied with a blush. "The lord of the Castle has been good, oh, so very good to my father, and I want to give him my dove, just to show how thankful I feel."

"Do you think that the lord of the Castle would value your bird?" asked the stranger, smiling kindly down on the child.

"I dare say that he has many more, and perhaps prettier birds," said poor Grace, and she looked wistfully at her covered basket as she spoke; "but Heartslove is so tame, so gentle —she will come at my call, and eat crumbs from my lips—he cannot have a more loving little dove. And then, sir, she is all that I have to give; so, perhaps, the great lord will not despise her."

"No; I will answer for it that the lord of the Castle will prize your bird dearly," answered the stranger, and his voice sounded so tender and loving that it seemed to Grace as if a father had spoken. "Give me your basket, my child; I will see that the dove reaches safely him to whom you would give it—he will most surely accept and value it for your sake."

Grace opened the basket, and pressed down her rosy lips to give one parting kiss to her Heartslove. She then closed down the lid, and with simple trust handed the basket to the stranger, who had opened the gate to take in her little present. The child then, after thanking him and dropping a curtsey, turned away from the gate.

Grace felt pleased to think that she had done what was right, that she had at least proved her wish to be grateful; and the remembrance of the noble stranger's smile lay warm at the little girl's heart. She liked to recall his words, "I will answer for it that the lord of the Castle will prize your bird dearly."

During the rest of that day Grace never spoke of her dove, though she thought of it often. Her parents were far too much occupied with their business to think of it at all, and, what was far more strange, not a word of gratitude towards their most generous benefactor was heard either from Seele or his wife. In the greatness of his gift, they seemed quite to have forgotten the giver. Grace alone resolved in her heart that not a morning or evening should pass without her blessing the name of the friend who had saved them all from ruin; and she smiled to herself as she thought of her gentle white dove nestling upon his bosom.

On the following day, as the family sat round the table at breakfast, talking over the purchases which Seele had made through the help of the lord of the manor, there was heard the tap of a bill at the window

"Oh! It's my dove—it's my own Heartslove; she has flown back again to her old home!" exclaimed Grace, starting up from her seat, and running to open the window

The child took the bird in, kissed and fondled it. Pleasant it was to her to stroke again the downy plumage, and to hear the coo of her pet.

"Look there, Grace!" exclaimed her father, "There seems to be something white tied under the wing of the bird."

There was indeed a small strip of paper, fastened with a bright thread of gold. Grace very eagerly untied it, wondering what kind of message her bird could have brought.

"There is something written, but I cannot read it. Please, father, tell me what it is!" cried Grace.

There was silence round the table, as Seele read aloud the contents of the paper to the circle of curious listeners. The writing was as follows:

"The child who gave this dove will be welcomed, if she come alone to the Castle at noon."

Grace to go to the Castle—Grace to be expressly sent for by the lord of the manor! Father, mother, brothers, and sisters all wondered at the message sent to the child. There could be no mistake about it; the lord's own signature was at the end of the note. It was read and re-read a dozen times over. Grace said less than did any one else, though she thought far more than them all.

"Won't you be afraid to go alone into the presence of the lord of the manor?" asked one of her sisters.

"I should be very, very much afraid," she replied, "only he has invited me to come."

"And what will you do when you see him?" inquired a brother.

"I will just give back Heartslove to her master," simply answered the child.

But very fast beat the heart of Grace, and her courage almost failed her when she had to pass alone the great iron gate, and walk up the stately avenue to the marble steps that led up to the Castle. She wished that she could have held her father's hand, or had her mother beside her. One thought, however, gave her strength to go forward. "The master has written that I—even I—shall be welcome. I have his own express invitation, so why should I fear to appear before him!"

So, with Heartslove, not now in a basket, but held in her bosom, the poor little grateful child drew nigh to the lord's magnificent home.

Grace was met by a kind-looking servant. "My lord has sent me to bring you to him," said the man. "Do not tremble, little one; my lord is very fond of children. See! He is coming down the marble staircase to receive you himself."

Grace eagerly, though timidly, raised her eyes to catch the first sight of her great benefactor, the mighty lord of the land. She had felt afraid to enter his presence, but all her fear passed away when she saw in the form advancing towards her, the same gentle stranger who had met her before at the gate, and who had taken charge of her dove.

"Did I not tell you that the lord of the Castle would prize your bird dearly?" he said, as he stooped and lovingly laid his hand on the head of the child.

Grace was then led by him through the Castle, its splendid galleries, its beautiful halls, where there was everything that could delight the eye of the beholder. In one apartment, she found a new dress awaiting her, spotless and white. She was left alone for awhile to put on the dress, and was then called to a rich feast spread out in a lofty hall. Grace, poor child as she was, then was allowed to sit down with the lord at his table, and to be helped to whatever she liked by his own princely hand.

Nor was her friend's kindness to end here. That most happy hour was but the first of many which Grace was to pass in that beautiful place. With the full consent of her parents, the lord of the Castle adopted the little girl as his own, and brought her up as his daughter. He lavished freely upon her every token of love, gratified every wish, and made the life of Grace so joyful, that every day seemed more bright than the last. And much did the lord value the bird which had been her first token of grateful affection; of all his treasures, none was more prized than the Heartslove of the child.

Shall I leave my young readers to find out for themselves the meaning of my little parable, or help them to trace out the lesson which it contains?

There is not one of them that has not a great Benefactor, to whose free bounty they owe a million times more than Grace and her family owed to the lord of the manor. Have they received all His benefits without a word of thanks, without a thought of grateful devotion? Have they offered nothing to their Heavenly Lord, who has freely forgiven them all their great debt, and loaded them with blessings day after day?

But perhaps a child may reply, "I have nothing to give to the Lord, no money with which to help His poor, no power of working for Him." This may be so, but oh, remember that you have still one offering which you can make; you have your Heartslove to lay at the feet of your Heavenly Friend. Be assured that the Lord will prize your love dearly, far, far more than all the earth's treasures of silver and gold. No being that has offered Heartslove in simple, grateful homage to his Saviour, but will be welcomed by Him to a glorious home in heaven, not to be received as a passing guest, but as a dearly beloved child, adopted into His family, and made happy for ever and ever with Him!

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