After the trail passes the spring it curves to the right through dry woods and meets a faint dirt road at the 1.4-mile mark. Return as you came. A pair of snow-capped volcanoes glare at each other from opposite sides of Diamond Lake. The older and taller of the two, Mt. Thielsen, wears a proud spire at its summit, a remnant of the lava plug that ended its eruptions many millions of years ago. The popular and very difficult Mt. Thielsen Trail climbs to the base of the summit spire.
Mt. Bailey is youthful by comparison, with a rounded summit and a small, lopsided crater.
The Mt. Bailey Trail is nearly as long and steep as the path up Mt. Thielsen. Because Mt. Bailey has no summit spire, hikers more often reach the top. Diamond Lake's basin once cradled a broad Ice Age glacier that descended from the flanks of Mt. Thielsen, Mt. Bailey, and Crater Lake's volcano, Mt. Mazama. A lake had replaced the glacier by the time Mt. Mazama's eruption sent a glowing avalanche of frothy pumice and hot gases racing at freight-train speed toward the North Umpqua River canyon. The lake did not vaporize under that hot blast, perhaps because smaller, earlier eruptions had left a thick blanket of pumice floating on the lake's surface as an insulating bridge.