Newberry Volcano is a large active shield-shaped stratovolcano located about south of Bend, Oregon, United States, east of the major crest of the Cascade Range, within the Newberry National Volcanic Monument. Its highest point is Paulina Peak. The largest volcano in the Cascade Volcanic Arc, Newberry has an area of when its lava flows are taken into account. From north to south, the volcano has a length of , with a width of and a total volume of approximately . It was named for the geologist and surgeon John Strong Newberry, who explored central Oregon for the Pacific Railroad Surveys in 1855.
The volcano contains a large caldera, in diameter, known as the Newberry Caldera. Within the caldera are two lakes: Paulina Lake and East Lake. The volcano and its vicinity include many pyroclastic cones, lava flows and lava domes; Newberry has more than 400 vents, the most of any volcano in the contiguous United States. Glaciers may have once been present at the volcano, though this remains contested. The area has a dry climate with low precipitation levels and little surface runoff.
The origin of the volcano remains somewhat unclear; while some scientists believe it originated from an independent hotspot, most evidence indicates that it formed from the subduction of the oceanic Juan de Fuca and Gorda tectonic plates under the continental North American Plate. Eruptive activity at Newberry Volcano began about 600,000 years ago and has continued into the Holocene, the last eruption taking place 1,300 years ago. Unlike other shield-shaped volcanoes, which often erupt basaltic lavas only, Newberry Volcano has also erupted andesitic and rhyolitic lavas. A popular destination for hiking, fishing, boating, and other recreational activities, the volcano lies within of 16,400 people and within of nearly 200,000 people, and it continues to pose a threat to life. Still considered an active volcano, it could erupt and produce lava flows, pyroclastic flows, lahars (volcanically induced mudslides, landslides, and debris flows), ashfall, earthquakes, avalanches, and floods. To track this threat, the volcano and its surroundings are closely monitored with sensors by the United States Geological Survey.
Geography
The center of Newberry Volcano lies to the south of the city of Bend, at the intersection of Deschutes, Klamath and Lake counties in Oregon, where it is one of the most accessible volcanoes in the state. It is the largest volcano in the Cascade Volcanic Arc at , and has roughly the same area as the state of Rhode Island at if its lava flows are included. Newberry lies east of the major crest of the Cascade Range in the High Lava Plains region, rising above its surroundings. From north to south, the volcano runs for a length of , with a width of and a total volume of about . Because of its enormous size and topographic prominence, it is often confused for an entire mountain range.
Newberry Volcano has a somewhat dry climate due to its location in the rain shadow of the Cascade Range. Climate data for the Newberry National Volcanic Monument are collected at the Lava Butte cinder cone, which had an average annual precipitation of from 2002 to 2012. Summer temperatures average from , dipping to average minimum and maximum temperatures of during the winter season. Spring has average temperatures of , while fall temperatures average . Each year, total precipitation consisting of winter snow and summer rain varies from in the highest parts of the region, and surface runoff rarely occurs even during heavy rain showers. Only one stream appears on Newberry's entire surface, and it remains unclear whether the volcano has ever been able to support glaciers on its slopes, since the mountain lacks cirques (amphitheater-like valleys formed by glacial erosion) or evidence of contact between lava and ice. However, displaced glacial erratics have been found far from their native areas, moraine sediment has been deposited on the eastern and northeastern slopes of the volcano, and the mountain's various cone features have "boat" shapes that indicate glacial alteration. The precise history of glaciers on the volcano is debated, but dry channels and dry waterfalls on the eastern and western slopes are evidence that the volcano once held water.