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).
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| 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.
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| Damselfly near North Mattieu Lake. |
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| 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.
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| 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.
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| ~270 degree panorama from Opie Dilldock Pass. |
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| North Mattieu Lake from the PCT. |
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| Cone of mountain hemlock, Tsuga mertensiana. |
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| A feeding moth. |
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| North Sisters with Castilleja in the foreground. |
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| A small stream cut through the overlying snow to form elegant shapes. |
