March 1995, Vol. 7, No.2

Thin Air is the news letter for the High Altitude Mountaineering Section of the Colorado Mountain Club. There are five issues of Thin Air each year: January, March, May,September, and November.

Next Thin Air deadline: April 6,1995

Contents

March HAMS Program

Makalu

Thor Kieser of Condor Adventures and leader of this March-May 1994 expedition will present his slides and commentary on the expedition's successful ascent of Makalu. The presentation will be made during the March HAMS Program, in the Colorado Mountain Club Auditorium, located at 710 10th Street, Golden, CO on Monday, March 20, 1995, at 7:00 PM. Golden. Public Invited, no admission fee.

At 8,841 meters, Makalu is the world's fifth highest mountain. Base camp was established at 5,300 meters on the Barun Glacier on April 2. The high camp was established April 28 at 7,700 meters. In the following weeks at least three different summit attempts were made in which Thor and other climbers made it to within 30 to 90 meters of the summit. On May 15, Anatoli Boukreev and Neal Beidleman stood on top of the true summit. This was the first Russian ascent and the seventh ascent by an American. Perhaps the major success of the expedition was that it was accident-free. There were no altitude, frostbite, crevasse or objective incidents. Congratulations to the team.

Ed Webster - "Three Faces of Everest"

The Unthinkable. Join Ed Webster as he describes his 'horrendous' 1988 adventure scaling a new route up the Kangshung Face of Mount Everest. This landmark climb cost Ed eight fingertips and three toes. Chris Bonington called it "amongst the finest examples of survival in the history of Himalayan mountaineering." Ed will include his 1985 attempt on Everest's West Ridge and his 1986 solo climb of Changtse via a new route. - Keith Jensen

Wednesday, March 15, 7 PM
American Mountaineering Center Auditorium
10th & Washington St.Golden, Colorado

Local retailers will be donating hundreds of dollars in door prizes. Tickets are $4 in advance at AAC, CMC, REI, EMS, and Neptune Mountaineering, or $5 at the door. This program is presented as a benefit for the American Mountaineering Center Building Fund, and is sponsored by:

HAMS SUMMITS ACONCAGUA AGAIN

by Terry Root

For the third time in five years, HAMS climbers have stood on the summit of Aconcagua. On January 25, all nine members of this year's team reached the top, making this the most successful trip yet. After an initial bout with bad weather that left nearly record amounts of new snow on the mountain; clear skies and low winds made for fast progress up the Polish Glacier route. However, due to avalanche and post-hole problems on the upper glacier, the decision was made on summit day to complete the climb by traversing to Independencia and finishing on the traditional Normal route, via the Caneleta. Summit day was cold but clear, and fresh snow in the Caneleta eliminated most of the usual slip and slide agony of the infamous scree. After that, it was back to Mendoza for the usual excellent steaks and wine.

This was the first time HAMS has taken the route up the Vacas Valley. This route is indeed much longer, but more beautiful and wild than the Horcones approach. Unfortunately, it is being discovered by increasing numbers of people attempting to avoid the circus up the Horcones. Guided groups, especially, are using this approach, including one with climbers and trekkers that numbered more than 50 people. The whole mountain in general is becoming a real zoo.

As the group had done a great job of training and planning, things went off without a hitch; no sickness or lost days. For leader Terry Root, it was his third trip to the mountain and by far the most trouble free. Credit goes to the climbers who did a lot of the pre- trip planning and work themselves, especially co-leaders Ken Yarcho and Joe Connell. The successful team included Doug Clark, Joe Connell, Doyle Dikes, John Goggin, Brett Roggenkamp, Terry Root, Tim Tiefenbach, Bill Worley, and Ken Yarcho.

Air Pressure: The Effects of Altitude, Latitude and Season

by Ward Hobert

The layer of air that covers our planet is insubstantial compared to the mass of the planet. The troposphere, which contains 80% of the atmospheric mass, only extends to 5 to 11 miles above the surface of the planet. This would correspond to no more than the thickness of a heavy layer of paint for a 10 inch classroom globe. The thickness of the troposphere is not uniform over the earth. A combination of centrifugal force and temperature differences make the troposphere thickest at the equator, 10 to 11 miles. It is only 5 to 6 miles thick at the poles. Due to lower temperatures the troposphere is more dense at the poles, and the net result of all contributing forces and factors is that air pressure is pretty much the same planet wide at sea level. At high altitudes this is not true.

Since the air layer over the earth is thinner at the poles, any upward movement from the planet's surface passes through a greater portion of the air layer than the same movement would accomplish at the equator. Thus, for higher altitudes, air pressure at high latitudes is lower than it is at low latitudes.

We can not quantify this effect until we address seasonality. In the winter the air mass over the poles cools and contracts, and the thickness of the planet's local atmospheric layer decreases. (Of course, the opposite pole is experiencing summer and its air layer is expanding.) Thus, in winter at high latitudes and high altitudes air pressure is further depressed.

Now, to quantify: consider the altitude at which air pressure averages 0. 5 atmospheres. On Mt. McKinley, 63: N latitude, this altitude is, on the average, 18,400 feet in mid-summer, and 16,800 feet in mid-winter. In the vicinity of Mt. Everest, 30: N latitude, this altitude is 19,400 feet in mid-summer, and 18,850 feet in mid- winter.

At the summit of McKinley, 20,320 feet actual altitude, the average air pressure in mid-summer is about 0.453 atmospheres, which would correspond to a Himalayan summer altitude of 21,650 feet. In winter the summit pressure for McKinley, 0.420 atm., corresponds to a Himalayan winter altitude of 22,800 feet, and a Himalayan summer altitude of 23,460 feet.

Chimborazo, 20,700 feet actual altitude, is essentially on the equator ( 2: S latitude) and so its summit pressure of about 0.472 atm. does not vary much seasonally.

Most of the information supplied here came from "The World's Great Mountains: Not the Height You Think", Terris Moore, American Alpine Journal 16:109, 1968.

For your information:

1 atmosphere = 760 mm Hg = 760 Torrs = 29.92 in. HG = 14.70 psi = 1.013 bars

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