Avalanche and ItsSafety

An avalanche is asudden and rapid flow of snow,often mixed with air and water,down amountainside .Avalanches are______(51)the biggest dangers in the mountains for

both life andproperty.

All avalanches arecaused by an over-burden of material,typically snowpack,that is too massive andunstable for the slope______(52)supports it. Determining the critical

load,the amount ofover-burden which is______(53)to cause an avalanche，______（54)acomplex task involving the evaluation of a number of factors.

Terrain slopesflatter than 25 degrees or steeper than 60 degrees typically have a low______(55)of avalanche .Snow does not______(56)significantly on steepslopes;also,

snow doesnot______(57)easily on flat slopes.Human-triggered avalanches have the greatestincidence when the snow's angle of rest is______(58)35 and 45 degrees;the

critical angle, theangle at which the human incidence of avalanches is greatest,is 38 degrees.Therule of thumb is:A slope that is______(59)enough to hold snow but steep

enough to ski hasthe potential to generate an avalanche,regardless of theangle.Additionally,avalanche risk increases with ______(60);that is,the more aslope is disturbed by

skiers,the morelikely it is that an avalanche will occur.

Due to thecomplexity of the subject,winter travelling in the backcountry is never 100%safe .Good avalanche safety is a continuous______(61),including route selectionand

examination of thesnowpack,weather______(62),and human factors.Several well-known good habits canalso______(63)the risk .If local authorities issue avalanche risk

reports,they shouldbe considered and all warnings should be paid______(64)to.

Never follow in thetracks of others without your own evaluations;snow conditions are almostcertain to have changed since they were made .Observe the terrain and note

obvious avalanchepaths where plants are ______(65)or damaged .Avoid travelling below others whomight trigger an avalanche.65._________

A.fresh

B. big

C.grown

D. missing