Glaciers

Sat 14 Mar 2015


Glaciers are large masses of ice on land that show evidence of past or present movement. They grow by the gradual transformation of snow into glacier ice. A fresh snowfall is a fluffy mass of loosely packed snowflakes, small delicate ice crystals grown in the atmosphere. As the snow ages on the ground for weeks or months, the crystals shrink and become more compact, and the whole mass becomes squeezed together into a more dense form, granular snow. As new snow falls and buries the older snow, the layers of granular snow further compact to form firm, a much denser kind of snow, usually a year or more old, which has little pore space. Further burial and slow cementation – a process by which crystals become bound together in a mosaic of intergrown ice crystals – finally produce solid glacial ice. In this process of recrystallization, the growth of new crystals at the expense of old ones, the percentage of air is reduced from about 90 percent for snowflakes to less than 20 percent for glacier ice. The whole process may take as little as a few years, but more likely ten or twenty years or longer. The snow is usually many meters deep by the time the lower layers art convened into ice.

In cold glaciers those formed in the coldest regions of the Earth, the entire mass of ice is at temperatures below the melting point and no free water exists. In temperate glaciers, the ice is at the melting point at every pressure level within the glacier, and free water is present as small drops or as larger accumulations in tunnels within or beneath the ice. Formation of a glacier is complete when ice has accumulated to a thickness (and thus weight) sufficient to make it move slowly under pressure, in much the same way that solid rock deep within the Earth can change shape without breaking. Once that point is reached, the ice flows downhill, either as a tongue of ice filling a valley or as thick ice cap that flows out in directions from the highest central area where the most snow accumulates. The up down leads to the eventual melting of ice.

Questions:

1. Which of the following does the passage mainly discuss?
(A) The effect of glaciers on climate    
(B) Damage from glaciers
(C) Glacier formation        
(D) The location of glaciers

2. Which of the following will cause density within the glacier to increase?
(A) Increased water and air content
(B) Pressure from the weight of new snow
(C) Long periods of darkness and temperature variations
(D) Movement of the glacier

3. The word "bound" in line 9 is closest in meaning to
(A) covered    
(B) chosen    
(C) planned    
(D) held

4. Which of the following will be lost is a glacier forms?
(A) Air    
(B) Pressure    
(C) Weight    
(D) Rocks

5. According to the passage, which of the following is the LEAST amount of time necessary for glacial ice to form?
(A) Several months        
(B) Several years
(C) At least fifty years        
(D) A century

6. The word "converted" in line 14 is closest in meaning to
(A) changed    
(B) delayed    
(C) promoted    
(D) dissolved

7. What is the purpose of the material in paragraph three (lines 16-19)
(A) To define two types of glaciers
(B) To contrast glacier ice with non-glacier ice
(C) To present theories of glacier formation
(D) To discuss the similarities between glacial types

8. In temperate glaciers, where is water found?
(A) Only near the surface        
(B) In pools a: various depths
(C) In a thin layer below the firm    
(D) In tunnels

9. The word "it" in line 21 refers to
(A) formation    
(B) ice    
(C) thickness    
(D) weight

10. It can be inferred from the last paragraph that a glacier
(A) can revert to a fluffy mass
(B) maintains the same shape throughout the glacial process
(C) is too cold to be thoroughly studied
(D) can contribute water to lakes, rivers, or oceans

Answers:

1)C 2)B 3)D 4)A 5)B 6)A 7)A 8)D 9)B 10)D

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