Newberry Caldera:
Oregon’s largest Volcano
Volcanology Term Paper

Figure 1: View of Newberry Caldera from Lava Butte. Photo by Lee Siebert, 1995 (Smithsonian Institution)

Newberry Caldera
Newberry volcano, situated east of the Cascade Range is one of the largest volcanoes in terms of its area in the lower 48 United States and is also the largest volcano in Oregon, covering an area of about 1600 sq. km. The low angle basaltic to basaltic-andesite composite shield is dotted with over 400 cinder cones; however the volcano also has a history of producing a number of major silicic eruptions, which are associated with the formation of the 6 by 8 km wide summit caldera that contains two caldera lakes. Despite the similarities, Newberry in fact is not a cascade volcano. Instead it belongs to a discontinuous belt of composite volcanoes lying parallel to the Cascades at a distance of 56-80 km. this discontinuous belt extends up to Mt. Simcoe east of Mt. Adams and south to Medicine Lake Volcano east of Mt. Shasta (Williams, 1935). Figure 2: aerial view of Newberry Caldera. Photo by Lee Siebert, 1998 (Smithsonian Institution).
The earliest eruptive products (<0.73 million years ago) (Ma) consist of a sequence of ash-flow and airfall tuffs. Caldera collapse is thought to be associated with major ash flows emplaced about 0.5 and 0.3-0.5 Ma. These eruptions were preceded by the emplacement of numerous mafic cones and vents and silicic lava domes and flows, many of which are aligned NNW and NNE parallel to regional fault zones The caldera of Newberry Volcano has also been the site of numerous Holocene eruptions of mostly rhyolitic composition, that occurred as recently as 1,300 years ago (Jensen, 1995).
Within the Caldera there are two lakes (Paulina Lake), cinder cones, lava flows and obsidian domes. The land area of the caldera is heavily forested except in