What is quicksand?

What is quicksand? It is a light, loose sand which is mixed with water. It does not look different from sands which might be right next to it. But there is a difference: quicksand will not support heavy ob­jects.

Quicksand usually occurs near the mouths of large rivers and on flat shores where there is a lay­er of stiff clay under it. Water is collecting the sand because the underlying clay keeps the water from draining away. This water may come from many different places, such as river currents or pools.

The grains of quicksand are different from or­dinary grains of sand because they are round in­stead of being angular or sharp. The water gets between the grains and separates and lifts them, so that they tend to flow over one another. This makes them unable to support solid objects.

Some quicksand is not even made of sand. It can be any kind of loose soil, a mixture of sand and mud, or kind of pebbly mud.

People who step into quicksand do not sink out of sight. Since it contains so much liquid, it will enable them to float. And since quicksand is heavier than water, people can float higher in it than they do in water.

The important thing is to move slowly in quick­sand. This is to give it time to flow around the body. Once it does this, it will act like water in which you are swimming.

Unit X. Test Section.

Ex. 1. Выберите правильный вариант из предложенных в скобках.

1. The more (soluble/solution/solvent) salts tend to stay in solution longer.

2. Being less dense than mantle, the (melts/melting/molten) crust-al material rises toward the ocean floor.

3. The phenomenon is rather complicated and the process (involving/involved/was involved) is not yet clear.

4. Land features on the continents may (to be divided/dividing/be divided) into mountains, plateaus, and plains.

5. The attraction of the moon is the chief force (causes/caused/causing) the tides.

6. The rotation of the earth (causes/is caused) day and night.

7. Erosion requires transportation of rock waste to a new (locate/ location/local).

8. In lakes the material (brings/brought/is brought) down by the stream settles on the bottom.

9. Metamorphism (change/changes/to change) the original char­acteristics of the rocks and minerals.

10. Earthquakes are geological (phenomena/phenomenon) that attend the deformation of the earth's crust.

11. Geological hazards frequently (result/cause/effect) in injuries or loss of life and property.

12. The highest rate of motion is observed in the middle of the ice stream, approximately along its (axis/axes/axe).

13. (Weather/whether) conditions also play a part in erosion.

14. Mountains result from the folding of rocks which were (formal­ly/former/formerly) flat.

15. When a rock is subjected (to/at/by) great pressure it splits into thin sheets.

16. All the given (datum/dates/data) show that erosion started long ago.

17. The destructive (effect/affect/effort) is much greater on uncon­solidated structures than it is on firm rock.

18. The (way/road/path) in which rocks deform under stress is de­termined by (their/there) composition.

19. The wind carries (lose/loose/losses) particles and with sand helps to wear away rocks.

20. Water soaks into rocks, (solves/dissolves) and alters minerals.

21. The winds carry (much/many) sand and dust.

22. An earthquake usually folds the (strata/straight) of the rocks.

23. Any snow (layer/liar) on a mountain side tends to creep down the slope under the influence of gravity.

24. The heat of the sun causes the rocks (to expand/to extend).

25. Rocks are (affected/effected) by alternate heating and cooling.

26. Tides (cause/are caused) by the attraction of the moon and the sun.

27. There is (little/few) hope that geologic hazards can be eliminated completely.

28. The change in fossil forms (causes/results/leads) from the change in conditions.

29. (Some/same) of the newest soils of the world are the glacial de­posits.

30. It is most important to realize that changes are (continue/continual/continually) taking place on the surface of the earth.

31. (Frequency/frequent/frequently) such stones roll into irregular depressions.

32. The greater (move/movements/movable) of the earth are of two kinds.

33. Soils of this type contain a lower proportion of minerals (resist/ resistant/resistance) to alteration.

34. In (some/same) regions glaciation has smoothed the topography and made the land more suitable for agriculture; in others it has pro­duced such roughness as to make the land useless.

35. Water has a strong (solve/solution/solvent) action on parts of the earth's crust.

36. The (loosen/loosening/loose) and removal of rock material by any process at the earth's surface is erosion.

37. The earth movements that cause the earthquakes may be either volcanic or tectonic; the (latter/late/later) type is more common.

38. Ground water is very (different/difference/differently) from rain water.

39. Volcanism includes all (phenomenon/phenomena) that are con­nected with molten rock matter and its movements.

40. (Like/likely) the earth the sun both rotates and revolves.

41. Metamorphism (changes/is changed) the original characteristics of the rocks and minerals.

42. Movements of the atmosphere (are caused/cause) important mod­ifications of the land.

43. Sometimes landslides (caused/are caused) by rain water.

44. Tsunami (is caused/caused) by an earthquake taking place on the ocean bed.

45. The forces of erosion carry away particles of (erode/eroded/eroding) rock.

46. Most of the land surface of the earth (covered/is covered) with soil.

47. Running water (affects/is affected) the landscape.

48. The sand particles (carried/are carried) along by wind.

49. At night when it gets very cold the water in the cracks freezes and its (expand/expansion/expansive) causes the cracks to widen.

50. Tides (cause/are caused) by the attraction of the moon and the sun.

51. Fold mountains (formed/forming) by folding in the earth crust.

52. The winds carry (much/many) sand and dust.

53. Chemical weathering is a (most/much more/much) complicated process than physical weathering.

54. The change in fossil forms (causes/results/leads) from the change in conditions.

55. Mountains result (in/from) the folding of rocks.

56. All the given (datum/dates/data) show that erosion started long ago.

57. Glaciers (like/likely) rivers and wind wear away the surface over which they move.

58. What causes such a (phenomenon/phenomena) as the magnetic field of the earth?

59. Alluvial diamond deposits in southern Africa were traced to the well known (course/source/cause), the Kimberlite pipes near the city of Kimberly.

60. There is (little/few) hope that geologic hazards can be eliminated completely.

61. When a rock is subjected (to/at/by) great pressure it splits into thin sheets.

62. The disturbance and dislocation of the earth's crust lead (from/ in/to) diastrophism.

63. An earthquake usually folds the (strata/straight) of the rocks.

64. Water soaks into rocks, (solves/dissolves) and alters minerals.

65. The formation of clay minerals is the direct result (at/of/from) weathering.

66. Rocks are (affected/effected) by alternate heating and cooling.

67. The process is (named/referred/called) to as denudation.

68. The distance the material travels depends (of/on/in) the size of the particle and the strength of the wind.

69. A glacier moves slowly down under the force of (gravity/gravel).

70. Erosion also proceeds (rapid/rapidly) along the lines of weakness.

71. Volcanic action may (create/creature/creative) islands, mountains and plateau.

72. Principle causes of land-surface subsidence are removal of solids or fluids from the land surface either (nature/naturally/natural) or ar­tificially.

73. The (transmit/ transmission/transmissible) of heat by the move­ment of particles themselves is known as convection.

74. Temperature (relationship/relative/relatively) is also important.

75. (Since/science) 1631 Vesuvius has been in a state of almost con­stant mild activity.

76. The greater (move/movements/movable) of the earth are of two kinds.

77. Erosion requires transportation of rock waste to a new (locate/ location/local).

78. Soils with a lower proportion of minerals are (resist/resistant/ resistance) to alteration.

Ex. 2. Изложите содержание следующих текстов по-английски