Avalanche 101 Lesson 2: Weather & Avalanches
The last lesson in Avalanche 101 touched upon terrain and slope angle. Remember, the Avalanche Triangle consists of Terrain, Weather and Snowpack. These three factors help contribute to Avalanche potential. This month's lesson will focus on weather and its involvement in Avalanches.
Avalanches typically occur during or after a storm where there is significant snowfall. The most critical time is 24 hours after a snowstorm. The three aspects of weather that are important concerning avalanches are snowfall, temperature and wind.
Snowfall
Significant snowfall produces additional stress on the
snowpack. The extra weight of new snow can actually cause weak
layers in the existing snowpack to break, many times causing
slab avalanches. Snowfall accumulation less than six inches
rarely causes avalanches. Keyword = Rarely! Accumulation of six
to twelve inches on new snow causes a serious threat to skiers
and climbers. And accumulation of twelve inches or more (which
happens in the mountains, A lot) can cause catastrophic
avalanches.
Temperature
Small changes in temperature over a short period of
time does not affect the snowpack as much as greater
temperature changes over a longer period of time. However, what
does help the snowpack is when snow melts and re-freezes. This
happens during the day (melting) and then immediately at
night (re-freezing). This melt/re-freeze process allows the
snow to bond stronger. What is concerning is when temperatures
either stay above or below freezing for a long period of time.
This does not allow the snowpack to bond adequately thus
causing potential weak layers in the snowpack.
Wind
Wind direction is very important for skiers and climbers. Wind
generally blows up one side of a mountain (Windward Side) and
then blows down one side of the mountain (Leeward Side).
Blowing up the "windward" side scours snow up and deposits it
on the "leeward" side. This extra deposition of snow on the
leeward side can cause instability in the snowpack. A tell tale
sign of snow scouring and deposition is cornices. It is
obviously safer to travel on windward slopes and climbers must
take caution when traveling on leeward slopes.
(Next month we will finish up our basic avalanche lessons with the third and final component of the Avalanche Triangle…Snowpack)
Missing On Mount McKinley 
Robert Link has returned to Mount McKinley for the 17th time! His last expedition was in 2001. At 11,000 feet Robert lost his left snowshoe used as a tent anchor. This was no ordinary snowshoe. It was used and worn by Grizzly Adams in several episodes of his hit television show.
To help aid Robert in the search is Garrett Madison, JJ Justman and a team of climbers. In addition to finding the shoes the team hopes to get lost along the way and end up on the summit of the highest peak in North America. We'll keep you informed of their progress.
Did You Know:
On the summit of Mt. Everest the barometric pressure has been
measured at 253 mmHg (millimeters of mercury), the PO2 (Partial
Pressure of Oxygen) of the inhaled air at 53 mmHg, the
alveolar PO2 at 37.6mmHg, and the alveolar PCO2 (Partial
Pressure of Carbon Dioxide) at 7.5mmHg (American Medical
Research Everest Expedition 1981). The climber was of course
acclimatized.
What does this mean? If these values had been obtained on a patient in an intensive care unit, the patient would be considered terminal. -NSP-OEC
Trivia: Air is made up of Oxygen, Nitrogen and Carbon Dioxide along with a small trace amount of rare gases.
Question: What percent does Nitrogen make up in the Earth's atmosphere?
A.21% B.50% C.78% D.17%
Send your answer to info@mountain-link.com. Include your name and answer in your email. We will take those with the correct answer and pull 1 name from the hat. The lucky winner will win a Mountain Link Logo T-Shirt. But remember...Everyone's a Winner...some...will be shirtless!
Winner will be announced May 30th!
Last Month's Trivia Question: According to National Geographic, how high does Mount Everest Grow per year? The Answer: 4 millimeters per year.
Kiss The Sky to Conquer
Diabetes 
Kate Noble is just one of 2 million children stricken with insulin dependant Diabetes. Diagnosed at the age of 1 and now 14, Kate has already suffered through 10,000 insulin shots, 33,500 blood checks and 500 insulin pump catheter inserts.
Kate's father has often said "I would travel to the ends of the earth and climb every mountain to find a cure for Diabetes." In June 2005 he will do just that.
Guided by Mountain Link, he and a small team will attempt to summit Huayna Potasi (19,975 ft) located in the Cordillera Real, Bolivia. The climb hopes to raise $250,000 of which 100% of every dollar donated will go to support the clinical trials investigating a potential cure for Diabetes at Massachusettes General Hospital.
Please follow our lead. You don't need an ice axe or crampons to be part of our team. All you need is to give with your heart. Every dollar will help bring us closer to finding a cure for Kate and the millions of other children just like her. To learn more and to contribute, click here
Adventures Worth Considering
Mont Blanc, France: September 4 - 9; Guides: Robert Link & Dan Windham
Everest Base Camp Trek/Island Peak Climb, Nepal: October 4 - November 2; Guides: Lhawang Dhondup & JJ Justman
Mountain Link "Tie In" brings the world of mountaineering to you with the latest tips and techniques, entertaining stories and beautiful mountain photos. Help us become the Number One source for aspiring adventurers. Please feel free to forward this newsletter to your friends.
