Olallie Butte is a steep-sided shield volcano in the Cascade Range of the northern part of the U.S. state of Oregon. It is the largest volcano and highest point in the distance between Mount Hood and Mount Jefferson. Located just outside the Olallie Scenic Area, it is surrounded by more than 200 lakes and ponds fed by runoff, precipitation, and underground seepage, which are popular spots for fishing, boating, and swimming. The butte forms a prominent feature in the Mount Jefferson region and is usually covered with snow during the winter and spring seasons.
Part of a stretch of shield volcanoes in Oregon with an unusually low elevation, meaning they have undergone less erosion over time than surrounding volcanic centers, Olallie has been excavated by glacial erosion on its northeastern flank. Its central volcanic plug has also been exposed. Comparisons of its morphology with Mount Jefferson suggest an age for the butte between 70,000 and 100,000 years; there is no evidence that it has erupted within the past 25,000 years. Olallie Butte has a steep, conical shape that serves as a transitional morphology between steep, mafic (rich in magnesium and iron) volcanoes like Mount McLoughlin and Mount Thielsen and flatter, mafic shields. It is made of basaltic andesite.
A Forest Service fire lookout tower was built on the summit in 1915 but abandoned in 1967; the summit also had a cupola cabin from 1920 until its roof collapsed in 1982. Olallie gets its name from the Chinook Jargon word klallali, which means berries. Today, the butte lies within the Warm Springs Indian Reservation. The Pacific Crest Trail passes over the western side of the butte, and there are other trails that reach the mountain's summit. Although the main trail to the summit is not well maintained, it still remains open to hikers.
Geography
Olallie Butte is located within Jefferson, Marion, and Wasco counties, all within the northwestern to north-central part of the U.S. state of Oregon. The volcano lies just outside the irregularly shaped Olallie Roadless Area, which lies within the Mount Hood National Forest to the west of the major crest of the Cascade Range and directly north of the Mount Jefferson Wilderness. This region encompasses of an upland area with small volcanoes, bordered to the southwest by the canyon wall of the North Fork of the Breitenbush River. It can be accessed from trails running from the Clackamas and Breitenbush River drainages, which reach the eastern and southern parts of the Olallie Area, as well as logging roads that enter the Olallie roadless area at its northern portion.
Williams (1916) reported that Olallie Butte had a number of small, unnamed lakes, particularly concentrated at its southern base, which were mostly shallow. According to Johnson et al. (1985), dozens of these lakes were carved by the movement of glaciers over Olallie Butte. Olallie Lake is the largest of more than 200 bodies of water near Olallie Butte's base and contained in the Olallie Lake Scenic Area in Mount Hood National Forest's southern segment. Fed by runoff, precipitation, and subsurface seepage, Olallie Lake otherwise has no clear source of inflow or outflow, nor do many other lakes in the Olallie Butte area. To maintain Olallie Lake's water level, a low dam was built on the Mill Creek outlet, which flows east to Long Lake. Shitike Creek heads between Olallie Butte and Mount Jefferson, coursing east to the Warm Springs community before it joins the Deschutes River.
Usually covered with snow in the winter and spring seasons, Olallie Butte is a prominent feature in the Mount Jefferson region. According to the U.S. National Geodetic Survey, Olallie Butte has an elevation of ; the Geographic Names Information System lists its elevation as , while Hildreth (2007) lists it at . It has a proximal relief and distal relief of and , respectively. Olallie Butte has a total volume of .
The cinder cone lies north of Mount Jefferson and to the northeast of Olallie Lake. Olallie Butte can be reached from Oregon Route 22 by following Breitenbush Road to the Olallie Lake Guard Station, then continuing on the main road along the transmission line. A trail to the summit of the mountain and a station runs for about from a trail marker located past a clearing on the main road; trucks cannot continue past this point.