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____1____ the biggest dangers in the mountains for both life and property. 　　All avalanches are caused by an over-burden of material, typically snowpack, that is too massive and unstable for the slope____2____ supports it. Determining the critical load, the amount of over-burden which is____3____ cause an avalanche, ____4____ acomplex task involving the evaluation of a number of factors. 　　Terrain slopes flatter than25degrees or steeper than60degrees typically have a low ____5____ of avalanche. Snow does not____6____ significantly on steep slopes; also, snow does not ____7____ easily on flat slopes. Human-triggered avalanches have the greatest incidence when the snow’s angle of rest1 is____8____ 35 and45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is38degrees. The rule of thumb2 is: A slope that is____9____ enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. Additionally3, avalanche risk increases with ____10____;that is, the more a slope is disturbed by skiers, die more lijkely it is that an avalanche will occur. 　　Due to the complexity of the subject, winter travelling in the backcountry4 is never 100% safe. Good avalanche safety is a continuous____11____,, including route selection and examination of the snowpack, weather____12____ and human factors. Several well-known good habits can also____13____ the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid ____14____ 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____15____ or damaged. Avoid traveling below others who might trigger an avalanche. 　　詞匯： 　　avalanche / '?v?l?nt?, -lɑ?n? / n.雪崩 　　snowpack / 'sn??p?k / n.積雪場 　　terrain / te're?n / n.地形，地勢 　　steep / sti?p / adj.險峻的，陸峭的 　　trigger / 'tr?g?(r) / v.引起，激發(fā) 　　incidence / '?ns?d?ns / n.發(fā)生(率) 　　ski / ski? / v.滑雪 　　complexity / k?m'pleks?t? / n.復雜性 　　注釋： 　　1.angle of rest：這里指積雪保持靜止的角度。 　　2.rule of thumb：指“a broadly accurate principle, based on experience or practice rather than theory”，即“通用法則，經(jīng)驗法則' 　　3.Additionally：是一個副詞，用來引人新的事實或論點，意為“此外”。 　　4.backcountry：人煙稀少的地區(qū)