Monday, July 09, 2007

Pansy Basin

This high glacial valley is of note floristically, geologically and hydrologically. It is located in the Bull of the Woods Wilderness Area at over 4000 ft. elevation. Locals can identify the area as being the next valley east from Bagby Hot Springs. Access is via Forest Service Roads 6340 and 6341. Two trails lead up the valley - the trail most traveled is the one on the maps, with a fairly even grade up the east side, and the hard to find older horse trail that crosses the basin floor and climbs (twice) the west valley wall. Early trail builders did not bother much with planning even grades for easier hiking - horses did the work. Distances then from the nearest road were much greater - in 1940 the trail to Pansy Basin was 25 miles, not one.

The Clackamas River Basin Council sponsored this excursion. I've lead these outings for a few years now, adding commentary similar to that in this article as we hike along.

Much of the basin is floored by a large post-glacier landslide including many blocks the size of furniture, even as large as automobiles. A guesstimate is for an event date 11,000 years back, probably not long after the glacier melted out from the valley. A look up the landslide scar on the west valley wall shows how it occurred. An ancient pumice deposit still hangs in a cliff above the boulders remaining from the slide.

Upper Pansy Basin
From Edge of Avalanche

Originally the soft pumice was fronted with hard basaltic rock, and the two separated, resulting in the rockfall. Only a little of the pumice moved. The slide is hundreds of feet long and its momentum carried it a ways up the far ridge. During extreme weather conditions, two lakes form atop these boulder fields, whose size is evident from shoreline deposits of trees and twigs. How is this possible?

Evidently the same rare conditions that bring flooding in low elevations are needed to form these temporary lakes. Cold temperatures freeze the soil, copious snow follows, and then the 'Pineapple Express' comes along - very wet tropical rainstorms that melt snow to the highest elevations and add many inches of rain too. These conditions make mountain travel difficult - snow and ice at low levels make for many miles in the cold rain on foot or ski in less than enjoyable conditions. Snowmobiles are illegal in the Wilderness Area though they could be used on the approach road to within a mile or so of the basin.

As no one has witnessed these two lakes, we must make deductions about them from the evidence they leave behind. The linear shoreline deposits of woody debris, including both small wood and whole trees, could only have been left by ponded water. No erosion features exist, so the high water must be short lived. The two lake sites are very different. The lower is deep and broad and consists entirely of rock just as left by the slide. The upper lakebed is mostly covered by organic soil washed in by the stream that enters over a falls from the east. Most of the time this stream simply vanishes into the rocky substrate beneath the soil. The lake however leaves behind a more spectacular record of its departure. The dried rushes and grasses which occupy the lowest levels of the lakebed are laid down in a circular pattern as the lake water wheels around the rocky openings which act as drains, circling just like water rapidly exiting a bathtub. The lower lake has a more subtle clue - the lichens growing on the boulders change below the high water mark. Evidently a species very common elsewhere on the slide does not tolerate the rare submergence events and leaves the lake locale to another species that does.

The disappearing waters of both lakes and stream reappears a mile or more downhill just past the parking area at the trailhead. During wet seasons springs appear uphill and squirt through the culvert walls beneath the Forest Service road.

Pansy Basin Falls

The stream flowing off Dickey Ridge into the basin has a pretty nameless falls. It drops into a rocky slot at its base and then flows off to one side towards the slide area. Early in wet seasons it reaches the meadow before disappearing, but at dryer times it is lost in the slide alder thickets which border the forest. Such was the case during this visit.

Vegetation zoning in Pansy Basin;
in the background rocks are
logs left on the temporary lakeshore

The meadow makes quite a show at its peak in late June. There are other areas with more floristic variety than Pansy Basin, but few with a better show. The clear vegetive zoning has deep blue larkspurs dominating the wettest, richest soils near the stream and red to orange Indian paintbrush in the dryer and thinner soils. Larkspur is there too but far fewer. In the low areas near the drains only rushes and grasses grow. Otherwise the salmon Jacobs ladder is scattered throughout the area, with the native orange columbine present in often rocky areas with only a little soil. 

Western Columbine

Cats ears are unusually abundant on the dryer sections. The European dandelion is present, no doubt brought in via horses decades ago. A few other species make scattered variations to the show.

Along the forest trail some forest floor plants were flowering well. Oregon anemone (Anemone deltoidea) was abundant in spots, as was Coralroot (Corallorhiza mertensiana). This leafless, saprophytic orchid is normally deep reddish purple, but we found a single very unusual yellow plant.

Oregon Anemone

A small lake is hidden away above Pansy Lake on the old trail. On this visit it was half dried up in comparison to the picture below from 2004. We are not sure why - this has not been a dry year, and snowpack was ample.

Green Lake

Pansy Lake itself though shallow is much larger. It is impounded by a hillock of moraine left behind in the final retreat of the glacier from this high valley.

Up the remains of the old trail from Pansy Lake (damaged in the 1996 floods) is a relict stand of 5 and 6 foot thick Douglas firs, all with fire scars from an ancient fire. That fire eliminated all trees but these few for miles in all directions. The lake no doubt broke the intense fire allowing these trees to survive. The yard thick veterans which have grown up since the blaze seem little in comparison with these Methuselahs. At this elevation (4200-4300 ft, 1300 m.) their size is surprising, and certainly indicates great age.

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