ASSESS AVALANCHE RISK

Pay at­ten­tion be­fore and dur­ing your hike to make sure you’re on solid snow.

Backpacker - - Skıll Set -

Be­fore hik­ing…

• Take a class. There’s no sub­sti­tute for ex­pert in­struc­tion (sign up for a course at AIARE.info).

• Check the avalanche forecast. Find your lo­cal re­port at avalanche.org. Note key fac­tors, like cer­tain ar­eas, as­pects, or el­e­va­tions to avoid.

• Start early. Wet snow freezes at night, sta­bi­liz­ing it, but warmer af­ter­noon temps can cause wet slides.

Fac­tors to con­sider

1) Slope an­gle. Avalanches most of­ten oc­cur on slopes be­tween 25 and 50 de­grees, and dry avalanches, which are re­spon­si­ble for the ma­jor­ity of avalanche-re­lated deaths, com­monly at 37 to 38 de­grees. Avoid hik­ing on or un­der those slopes.

2) As­pect. In the North­ern Hemi­sphere, north-fac­ing slopes re­ceive less sun than south-fac­ing slopes in win­ter. The snow­pack on colder slopes is more likely to de­velop per­sis­tent weak lay­ers, which in­hibit sta­bil­ity. 3) Nat­u­ral an­chors. Snow on slopes with lots of vis­i­ble trees and rocks is less likely to break loose as one piece. Only a few trees or rocks? Those sig­nify a lo­cal­ized shal­low spot, where the snow­pack could be in­suf­fi­ciently an­chored to the slope. Avoid these.

4) Slope shape. Snow stretched over un­du­lat­ing slopes, es­pe­cially con­vex hill­sides, is un­der more stress than straight or con­cave slopes, mak­ing avalanches more likely.

Red Flags

• “Whumpf­ing.” When a denser top layer of snow col­lapses onto a weaker layer be­neath it, it cre­ates a deep, re­ver­ber­at­ing “whumpf” sound.

• Shoot­ing cracks. Step­ping on un­sta­ble snow can cause it to crack and sep­a­rate from the slope.

• Cor­nices. Wave-shaped heaps of snow at the apex of a ridge mean wind has de­posited a heavy layer on the slopes be­neath, mak­ing them likely to slide. Cor­nices can also snap off, trig­ger­ing those slopes.

• Re­cent avalanche ac­tiv­ity. Look for scraped hill­sides with clumpy snow de­bris at the bot­tom. Clean, white blocks with sharp edges, and/or vis­i­ble, gi­ant snow­balls mean the slide hap­pened within days.

• Pin­wheels. Rolling balls of snow por­tend wet slides.

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