Avalanche Vocabulary and Expressions snowslide entrain snowmobiler

游客2023-12-29  16

问题 Avalanche
Vocabulary and Expressions
snowslide     entrain        snowmobiler     serac collapse
snowslip      spontaneous    seismic         endemic [br] What condition is necessary for the forming of a powder snow avalanche?
Avalanche
   An avalanche, also called a snowslide or snowslip, is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength but sometimes only with gradually widening. After initiation, avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow. If the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current.
   Slides of rocks or debris, behaving in a similar way to snow, are also referred to as avalanches. The remainder of this article refers to snow avalanches.
   The load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches. Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may also trigger the failure in the snowpack and avalanches.
   Although primarily composed of flowing snow and air, large avalanches have the capability to entrain ice, rocks, trees, and other material on the slope, and are distinct from mudslides, rock slides, and serac collapses on an icefall. Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. Avalanches are most common during winter or spring but glacier movements may cause ice and snow avalanches at any time of year. In mountainous terrain, avalanches are among the most serious objective natural hazards to life and property, with their destructive capability resulting from their potential to carry enormous masses of snow at high speeds.
   There is no universally accepted classification of avalanches—different classifications are useful for different purposes. Avalanches can be described by their size, their destructive potential, their initiation mechanism, their composition and their dynamics.

选项 A、The avalanche moves in moderate speed.
B、The avalanche moves in slow motion.
C、The avalanche moves quick enough.
D、The avalanche moves with debris.

答案 C

解析 根据原文“If the avalanche moves fast enough…forming a powder snow avalanche…”判断,雪崩运行速度足够快是其必要条件,故本题应该选C。
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