Mt. Thielsen Trip Report: April 29, 2012 Outing Organizer: Geoff Hance, with Brent McGregor Elevation Gain: 3,800 feet, over warming snow, with an exposed summit block Distance: About 9 miles round trip Skills: Climbing, and descending, in crampons across a steep, soft snow field; ice ax self-arrest, easy scrambling, and steep downhill snowshoe travel. Cascades Mountaineers Climbers: Eric Buckland, Glenn Troullier, Geoff Hance, Brandon Simonds, Frank Florence, and Katie Tremayne. Everyone was on time and ready to go, despite waking up at 3AM Sunday morning. We met at the Walmart parking lot in south Bend at 4:15, and departed in two vehicles at 4:30. The drive to the Mt. Thielsen Trailhead took about 1 3/4 hours, including one brief stop. After gearing up, we departed the parking area at 6:40 AM, lead by Brent McGregor and Eduardo Cartaya, plus two additional members of the Central Oregon High Desert Grotto, or ten in total.
The trail started up gradually, following markers, until we veered up a more direct and steeper minor ridgeline, marked by some light prior traffic, which eventually produced our first glimpse of the iconic Mt. Thielsen summit, elevation 9,184 feet. As we gained elevation, Mt. Bailey and Diamond Lake also became visible. Due the glorious weather and exertion, initial outer layers were quickly shed. Eventually, the approach ridge joined with the mountainʼs main western ridgeline, which served as the approach, skirting an avalanche zone snow bowl on the left, and a sparcely wooded slope on the right. Snowshoes were switched for crampons. Eventually, we stashed the snowshoes to lighten loads.
Mt. Thielsen, or Big Cowhorn, is an extinct shield volcano in the Oregon High Cascades, between Mount Bailey and Diamond Lake. Because Mt. Thielsen stopped erupting 250,000 years ago, glaciers have heavily eroded the volcano's structure, creating precipitous slopes and its horn-like peak. The spire-like shape of Thielsen attracts lightning strikes and causes the formation of fulgurite, an unusual mineral. The prominent horn forms a centerpiece for the Mt. Thielsen Wilderness. This picture of the snow bowl to the left of the approach ridgeline shows some good avalanche evidence, with a clear dry slab avalanche zone in the upper middle, and what appears to be older remnants of prior dry loose avalanche activity in the lower left area, just above the tree line. The ridgeline approach was a series of blown snow drifts, with some cornicing becoming visible from further up the slope. We followed the ridge up until a traversing route led right onto the snow field.
The route meanders generally to the east, traversing up and over a steepening snowfield, and around various lava rock intrusion formations. The snow conditions started to deteriorate as temperatures rose, but the total lack of wind, and just a slight cloudy/hazy sky, helped produce exceptional views. Eventually, climbers were down to one layer, with Glenn climbing in short sleeves. The climb continues up and over, to the right, with the steepening grade requiring more switchbacks, with rising elevation. The snow was mushy, but post-holing was limited to about 12 inches, and was only a periodic nuisance. In time, the summit blockʼs south face and approach couloir beckoned.
At the top of the coulior, there is a small saddle that acts as a staging area for the summit block ascent. However, this area was somewhat drifted over, creating a bit more crowding than occurs during a summer outing. The summit block was almost entirely clear of snow, with some water features and small remaining snow patches. The team of six CM climbers, plus the two summiting members of the Central Oregon High Desert Grotto participants, opted for a fixed rope set-up with an ascender assist. While this scramble is moderately easy in the summer without protection, the patchy snow and water suggested the need for added caution. Plus, hauling a 70 meter, 8.2 cm diameter rope up to the summit argued in favor of actually using it.
For those who are considering Mt. Thielsen, the summit block climbing is not difficult, as the rock is broken up into fairly large chunks, with ample foot placements and decent handholds. Some agility and balance is required, however, and prior climbing activity is suggested, given the exposure.
Frank filled in the summit log for the club while Katie enjoyed a summit peak perch, which included views of the Crater Lake Caldera in the south, Diamond Peak to the NW, and the Middle and North Sisters, Broken Top, Bachelor to the north. The photo below is of the aforementioned Crater Lake caldera, with Mt. Scott on the left.
After a well earned summit pose, we practiced our rapelling skills back down to the base of the summit block. Rapelling was rather tricky given the irregular nature of the blocky summit face, thus requiring good footwork, rope control, and balance. With crampons back on, we started the descent about 3:00 PM.
We essentially retraced our steps on the descent, arriving back at the parking lot 12 hours after we left. On such a hot day, three quarts of fluids are recommended, as most of us ran through our 2 to 2 1/2 quarts. We tended to linger a bit during stops for water, pictures, food and equipment adjustments, as well as on the summit. With ten climbers, we also dedicated additional time to group consolidation. The soggy snow conditions slowed progress somewhat as well. Thus, the total time out was a bit more than anticipated. But, with such great weather, no one cared. The very enjoyable, somewhat relaxed pace made for a wonderful outing with great people. Special thanks go out to Brent McGregor for offering to include Cascades Mountaineers in his original outing planned for Central Oregon High Desert Grotto members. Prepared by Geoff Hance