The earlier pumice flows raced onward to Diamond Lake. Exactly what happened when they reached the lake can only be conjectured. This much, however, seems certain: the flows passed across the lake and made their exit down Lake Creek. They followed this for 5 miles before splitting into two branches at Toolbox Meadows, one branch turning westward to empty into the valleys of Lava and Clearwater creeks, while the other continued down Lake Creek and joined the North Umpqua River. An enormous volume of coarse pumice must thus have been discharged into the North Umpqua, and much of it was washed downstream for many miles. Between 25 and 30 miles below Toketee Falls, there are banks of washed pumice including lumps 6 inches across; about 20 miles below the falls, near Panther Leap, the tops of the pumice banks lie 20 feet above the river. In many places, these washed deposits carry charred logs.
It may be argued that all the pumice north of Diamond Lake must have been washed into place by rivers, that it would have been impossible for the flows to cross a body of water 3 miles in length. Yet the flows did somehow traverse the lake, for the deposits bordering Clearwater Creek show no trace of stratification. Had they been washed thus far by streams, they would surely show bedding, and the pumice lumps would show considerable rounding. Moreover, the deposits carry logs of charred wood that lie at random, and in places they are characterized by the pink color indicative of fumarolic action. They must therefore have been hot and gas-charged when they came to rest. Not until the flows had traveled approximately 10 miles beyond Diamond Lake did they lose their own propulsive force. Presumably, when the first onrush of pumice entered the lake, the light ejecta remained on the surface, forming a blanket across which the later waves of pumice poured as if on dry land. How else could they have retained their heat and gas?
Though much of the pumice that crossed Pumice Desert poured into Diamond Lake, and much of it, as we have seen, turned westward into the valley of the Rogue, the most voluminous flows were deflected eastward through the depression between the slopes of Mount Thielsen and Timber Crater. These flows crossed a low saddle in the crest of the Cascade Range and continued for another 20 miles, as far as the site of the present village of Chemult. Their total journey from the source was therefore more than 30 miles, though the slopes down which they moved were extremely gentle. The buoyancy and mobility of the mass was such that at Beaver Marsh, 6 miles from the snout of the flow, the deposits carry many bombs of pumice up to 6 feet across, and one as much as 14 feet in maximum dimension.
In the vicinity of Chemult, near the margins of the flows, the coarse, unbedded lump pumice is overlain by fine pumice, much of which is almost pure glass dust (histogram 252, figure 21). East of Beaver Marsh, on the road to Willow Spring, fine crystal-lithic ash and pumice lie on the deposits of the flows as well as on the older pumice fall beyond. These ejecta probably represent the settling of the finer constituents which rose in swirling clouds near the margins of the flows.
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