Nature’s Gigantic Snow Plough
On January 10, 1962, an enormous piece of glacier broke away and tumbled down the side of a mountain in Peru. A mere seven minutes later, when cascading ice finally came to a stop ten miles down the mountain, it had taken the lives of 4,000 people.
This disaster is one of the most ___devastating____ examples of a very common event: an avalanche of snow or ice. Because it is extremely cold at very high altitudes, snow rarely melts. It just keeps piling up higher and higher. Glaciers are eventually created when the weight of the snow is so great that the lower layers are pressed into solid ice. But most avalanches occur long before this happens. As snow accumulates on a steep slope, it reaches a critical point at which the slightest vibration will send it sliding into the valley below.
Even an avalanche of light power can be dangerous, but the Peruvian catastrophe was particularly terrible because it was caused by a heavy layer of ice. It is estimated that the ice that broke off weighed three million tons. As it crashed down the steep mountainside like a gigantic snow plough, it swept up trees, boulders and tons of topsoil, and completely crushed and destroyed the six villages that lay in its path.
At present there is no way to predict or avoid such enormous avalanches, but, luckily, they are very rare. Scientists are constantly studying the smaller, more common avalanches, to try to understand what causes them. In the future, perhaps dangerous masses of snow and ice can be found and removed before they take human lives.
28. The first paragraph catches the reader’s attention with a ___ ___.
A. firsthand report
B. dramatic description
C. tall tale
D. vivid world picture
29. In this passage ___devastating____ means ______
A. violently ruinous
B. spectacularly interesting
30. The passage is mostly about ______.