Avalanche and Its Safety
An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are among the biggest dangers in the mountains for both life and property.来源：www.examda.com
All avalanches are caused by an over-burden of material, typically snowpack, that is too massive and unstable for the slope that supports it. Determining the critical load, the amount of over-burden which is likelyto cause an avalanche, is a complex task involving the evaluation of a number of factors.
Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low risk of avalanche. Snow does not gather significantly on steep slopes; also, snow does not flow easily on flat slopes. Human-triggered avalanches have the greatest incidence when the snow's angle of rest is between 35 and 45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is 38 degrees. The rule of thumb is: A slope that is flat enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. Additionally, avalanche risk increases with use ; that is, the more a slope is disturbed by skiers, the more likely it is that an avalanche will occur.
Due to the complexity of the subject, winter travelling in the backcountry is never 100% safe. Good avalanche safety is a continuous process , including route selection and examination of the snowpack, weather conditions , and human factors. Several well-known good habits can also reduce the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid attention to. Never follow in the tracks of others without your own evaluations; snow conditions are almost certain to have changed since they were made. Observe the terrain and note obvious avalanche paths where plants are missing or damaged. Avoid traveling below others who might trigger an avalanche.
雪崩和安全问题
雪崩是雪掺杂着空气和水沿着山体突然迅猛地滑动造成的。雪崩是造成山区人们生命和财产安全的最大危险之一。
所有雪崩都是由于物质的过渡负荷造成，通常是积雪堆积过厚，很不稳固，超出了山坡面的承载能力。要确定山坡的临界承载量，可能造成突然雪崩的负荷量是一项很复杂的任务，需要衡量多个因素。
通常倾斜度小于25度，大于60度的山坡发生雪崩的可能性要小一些。积雪不会在陡峭的山坡上大量堆积，同样也不会在平缓的山坡上快速滑动。当雪在静止状态下的角度在35-45度之间，最可能发生人为触发的雪崩。人为引发雪崩的临界角度是38度，是最易人为引发雪崩的角度。常规经验是：一个平缓的足以堆积积雪，同时陡峭的适合人们滑雪的山坡，无论角度如何，都有可能产生雪崩。此外，雪崩的危险随着使用的增加而增加，换言之，滑雪者活动得越频繁，雪崩的可能性越大。
由于雪崩研究的复杂性，冬天在人烟稀少的地区旅行从来不是百分之百的安全。很好地躲避雪崩，保持安全是一个连续的过程，包括选择路线、检查积雪、了解天气状况及其他人为因素。以下几个广为人知的好习惯也可以降低风险：如果当地权威部门发布了雪崩警报，你应当予以考虑，加以注意。绝不要不加审度，就立刻接受他人意见。积雪自形成的那时就几乎注定要发生变化。认真观察地形，注意明显的雪崩路径：没有植物或植物被毁坏的地方。不要在那些可能引发雪崩的人或事物下面行走。