Rocky Butte (previously known as Mowich Illahee and Wiberg Butte) is an extinct cinder cone butte in Portland, Oregon, United States. It is also part of the Boring Lava Field, a group of volcanic vents and lava flows throughout Oregon and Washington state. The volcano erupted between 285,000 and 500,000 years ago. As part of the Boring Lava Field, Rocky Butte is considered an outlier of the Cascade Range. It was produced by the subduction of the oceanic Juan de Fuca tectonic plate under the North American tectonic plate; it is the core remnant of intrusive rock from kilate Pleistocene volcano. The Butte has a calc-alkaline composition and consists of basaltic andesite with olivine phenocrysts. Historically, the mountain was the home of the Rocky Butte Jail, Judson Baptist College, and Hill Military Academy, as well as an extensive Works Progress Administration construction project; it is also the site of a still functioning but decommissioned airway beacon, Portland Bible College, and a campus for the City Bible Church. The slopes of Rocky Butte currently support Joseph Wood Hill Park and the Rocky Butte Natural Area, which includes a wide variety of flora and fauna and supports rich forest stands. Located next to Interstate 205, the Butte is a popular destination for hiking, climbing, and seeing mountains from its summit viewpoint. Geography Rocky Butte lies in the northeast part of Portland within the city limits, in Multnomah County, part of the U. S. state of Oregon. It is one of the few smaller volcanic cones within or near Portland, along with Mount Tabor, Kelly Butte, and Powell Butte. According to the U.S. National Geodetic Survey, Rocky Butte has an elevation of . It is surrounded on almost all sides by the Portland Delta. With a variable topography, the Portland area ranges from river valley floors to terraces reaching elevations of . The Willamette Valley is separated within by hills reaching heights more than , and it is also physically separated from the lower Columbia River valley. The Columbia River flows west from the eastern Portland region, merging with the Willamette near Portland before moving north. Tributaries for the Willamette include the Pudding, Molalla, Tualatin, Abernethy, and Clackamas Rivers, while the Washougal and Sandy Rivers mark notable tributaries for the Columbia River. The Columbia River has significantly shaped the geology of the area. Portland's climate is moderate, with long growing seasons, moderate rainfail,