Newberry Volcano is a large, active, shield-shaped stratovolcano located about 20 miles (32 km) south of Bend, Oregon, United States, 35 miles (56 km) east of the major crest of the Cascade Range, within the Newberry National Volcanic Monument. Its highest point is Paulina Peak. Newberry is the largest volcano in the Cascade Volcanic Arc, with an area of 1,200 square miles (3,100 km2) when its lava flows are taken into account. From north to south, the volcano has a length of 75 miles (121 km), with a width of 27 miles (43 km) and a total volume of approximately 120 cubic miles (500 km3). 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, 4 by 5 miles (6.4 km × 8.0 km) 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 19 miles (31 km) of 16,400 people and within 62 miles (100 km) 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 20 miles (32 km) 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 620 square miles (1,600 km2), and has roughly the same area as the state of Rhode Island at 1,200 square miles (3,100 km2) if its lava flows are included. Newberry lies 37 miles (60 km) east of the major crest of the Cascade Range in the High Lava Plains region, rising 3,500 feet (1,100 m) above its surroundings. From north to south, the volcano runs for a length of 75 miles (121 km), with a width of 27 miles (43 km) and a total volume of about 140 cubic miles (600 km3). 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 17.9 inches (455 mm) from 2002 to 2012. Summer temperatures average from 73 to 82 °F (23 to 28 °C), dipping to average minimum and maximum temperatures of −1.8 to 68.9 °F (−18.8 to 20.5 °C) during the winter season. Spring has average temperatures of 60 °F (16 °C), while fall temperatures average 67 °F (19 °C). Each year, total precipitation consisting of winter snow and summer rain varies from 9.8 to 29.5 inches (25 to 75 cm) 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.
The volcano has two crater lakes, Paulina Lake and East Lake, which are filled by precipitation and percolation of ground water. Paulina Lake occupies an area of 1,530 acres (6.2 km2) and reaches a maximum depth of 250 feet (76 m), and it is separated from East Lake by a narrow isthmus, which is composed of rhyolite lava. East Lake has a smaller area of 1,050 acres (4.2 km2) with a maximum depth of 180 feet (55 m). The lakes have historically flooded channels surrounding the volcano. A large flood between 4,000 and 2,300 years ago released up to 12,000 acre feet (0.0148 km3) in volume from Paulina Lake, filling the valley floor above the Paulina Prairie, downstream of the lake. It was possibly caused by the failure of a rock ledge 5 feet (1.5 m) in height, rather than eruptive activity. Another flood took place in 1909 on the Deschutes River downstream from where it meets its tributary the Little Deschutes River.
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