Green Lakes, Three Sisters Wilderness

Broken Top with the southern-most of
the Green Lakes in the foreground.

Last week we took the kids on their first backpacking trip to the Three Sisters Wilderness in the central Oregon Cascades. During the summer of 2012, I took two day trips to the northern side of the wilderness near the Mathieu lakes area, so this time we ventured into the eastern part, heading west from Bend.

The Green lakes trail starts near where Fall Creek empties into a broad alpine expanse that is part meadow and part lake. The trail tends to closely follow Fall Creek northward where it tumbles out of a valley. At the height of the summer the cold water was still moving briskly and there were a few waterfalls and rapids along the several miles between the trail head and the point where the creek emerges from the Green Lakes basin. Along the banks of the creek, there were myriad flowers and wetland plants including orange and pink paintbrushes and Delphiniums.

At about 6500 foot elevation, the valley opens northward into a large basin that is home to the three Green lakes. The basin is a beautiful jewel nestled in between two of the tallest peaks in the Oregon Cascades: South Sisters to the northwest (10,358 ft) and Broken Top to the east (9175 ft). From different points within the basin, Mt Bachelor (9068 ft) and one of the companion Sister peaks are also visible. Both South Sisters and Broken Top have small glaciers according my copy of a USFS map. However, while South Sisters had some lingering patches of snow, it was hard to consider these glaciers per se. A warming climate is threatening the persistence of glaciers worldwide, and I wonder if these smaller glaciers in the Pacific Northwest are particularly vulnerable to rapid demise.



Fall Creek

Our camp was located just some 100 m east of Fall Creek near the point where it begins to leave the basin and tumble down into the valley that we had ascended. In this area the creek was lined with willows growing as dense shrubs no more than 1-2 m high. We also found numerous black tadpoles in the shallow creek, with fat oval bodies and eel-like tails. The older kids had fun catching them.

Immediately west of the valley was an extensive lava field with little apparent vegetation. The field had dark boulders of shiny obsidian mixed with the milder colors of volcanism: light and medium greys and orange. We noted that many of the rocks of the lightest grey color were extremely light weight for their size; I found that one could easily snap the smaller ones in half.



Plants along the edge of Fall Creek. I don't
know this species, but the flowers had the
very distinct smell of watermelons!

The slopes of South Sisters itself had little vegetation, but were composed of some scattered snow patches, fields of grey volcanic rubble and a streak of reddish rock near the summit. Along much of the trail, the forest seemed to be composed mostly of mountain hemlock, though there were firs and pines present as well. I do not recall seeing a single broadleaved tree. Much of the remaining vegetation was low lying shrubs and herbaceous plants, particularly in the more open volcanic meadows around Green lakes. Despite the rugged landscape, many plant species were in bloom, giving the harsh terrain an elegant vibrancy.

Sisters

The three snow-capped peaks of Sisters, each rising to over 10,000 ft, sit right in the middle of the Oregon Cascades. To the north are Mts. Washington and Jefferson. The Sisters peaks are home to many of the glaciers found in the state of Oregon (1). The wilderness that surrounds the three peaks was created in 1964 and is part of the Willamette and Deschutes National Forests (1). At 439 square miles, it is the second largest wilderness in Oregon (2).




South, Middle and North Sisters from the south. Photo by Lyn Topinka, USGS, summer 1985.

28 July 2012. I entered the wilderness from the Lava Camp Lake trailhead, just east of McKenzie Pass and stopped at South Mattieu Lake along the Pacific Crest Scenic Trail (PCT). Here there was essentially a ridge (Scott Pass) at about 6000 ft with the mountains dropping to the west and into the plateau of central Oregon to the east. It was a warm day, but in the evening there were now gusts of wind that started to chill me. This lake was tiny, perhaps only an acre or two in size. I took the PCT south to the western side of Yapoah Crater. The crater was a steeply-sloped and nearly barren hill of volcanic rubble. There were lava fields present throughout the northern part of the wilderness – grey in some places, rust colored in others. Firs, mountain hemlock, and pines comprised the forest at lower elevations but up near the base of Yapoah Crater (elev ~6250 ft), the trees were mostly mountain hemlock with some interspersed pines.

There were quite a few ghost trees at higher elevations in the wilderness – dead mountain hemlocks (or other species) that add an element of history to the landscape. These trees, sometimes silver with the sun low on the horizon, still stood tall but had variously broken-off limbs. Piece by piece they will decay and lend greater depth to the forest’s history. Plant life here is determined by the availability of soil. There were vast fields of barren volcanic rock inhospitable for woody species. Even then, where there was soil, the trees were small. A few herbaceous plants were in bloom – lupines and a common blue trumpet-shaped flower that hangs on in the smallest patches of soil amid the rubble. The north peak of sisters came into view at various times along the trail. A decent percentage of its slopes were still covered in snow. Mts Jefferson and Washington were easily visible to the north. There were a few tiny meadows or drying pond basins there. At one opening in the forest, dragonflies danced about in abundance. Perhaps foraging in the warm air, they would not settle for even the slightest moment so that I could get a decent photograph.




Damselfly near North Mattieu Lake.




Lupines.

11 August 2012. I entered the wilderness as I did two weeks ago, but pushed further south along the PCT than before. I arrived at a wonderfully beautiful alpine meadow where the Scott Trail meets the PCT. A few channels cut through this flower-filled basin much like shallow tidal channels in an estuary. There was just a trickle of flowing water in a creek, probably sourced mostly by continuing snow melt. The meadow was sprinkled with bright pinkish-red paint brushes (Castilleja), bluish-purple lupines (Lupinus) and yellow buttercups (Ranunculus). Small sedges, mosses and rushes contributed to the low-lying carpet of vegetation in the valley. There were also extremely dwarf shrubs that appeared to be willows – such a stark contrast to the tree habit these plants have elsewhere! Even though this was a meadow for all practical purposes, I did not notice any grasses. Interestingly, in their place, other plant families have filled in the dense, but very low-lying vegetation. It would be interesting to study the effects of the annual snowfall on the plants in this ecosystem: Are most of the species annuals? How long is their growing season? Can individual plants survive many months under thick snow cover or in frozen ground?

Continuing south along the PCT, I reached the Opie Dilldock Pass area and stopped on a barren ridge of sharp cinders. At ~6800 feet elevation, I had reached a zone of snow patches. The air was very warm and the remaining snow was rapidly melting. I was now near treeline though in some places the trees extended higher than my current elevation. From this vantage point, there was a wide vista of central Oregon, obscured only by a hazy sky and the even higher peaks present to the east and south.



A 180 degree panorama of an alpine meadow at about 6300 ft elevation. North Sisters (L) is to the south.

The Cascades are a relatively young mountain range having formed starting about 7 million years ago (3). Subduction of the small Juan de Fuca plate under the North American Plate in the Pacific Northwest provides the friction that generates magma production and builds the volcanoes (4). The mountains lie in a gently curving chain from southern British Columbia to northern California. Mt. Shasta and Lassen Peak are the southernmost of the Cascades in California. Geologically, the region is very active, with many of the major mountains having erupted in the last several thousand years (5). The two northern peaks of sisters are considered dormant, but South Sister erupted as recently as 2000 years ago (1). The Cascade Volcano Observatory of the US Geologic Survey monitors volcanic activity in the region.



~270 degree panorama from Opie Dilldock Pass.

North Mattieu Lake from the PCT.

Cone of mountain hemlock, Tsuga mertensiana.



A feeding moth.

North Sisters with Castilleja in the foreground.

A small stream cut through the overlying snow to form elegant shapes.