Access: Flows are located within the Newberry National Volcanic Monument; a permit is required for collection of all obsidian located within the boundaries of the national monument (strictly enforced). Access to the caldera is blocked by snow during the winter months.

Geologic Age: Post-Mazama (younger than 6,845 +/- 50 ¹⁴C years B.P.). Hydration rim measurements of the different flows suggest that the Interlake and Game Hut flows erupted at 6,400 years ago and were followed by the extrusion of the Central Pumice Cone Flow (approximately 4300 years B.P.) and East Lake Flows (approximately 3,400 years B.P.)(Friedman 1977; Friedman and Trembour 1978; Friedman and Obradovich 1981).

Chemical Composition: The major and/or trace element composition of obsidian from the flows that make up this source group are reported in Jack and Carmichael (1969), Laidley and McKay (1971), Higgins (1973), Beyer (1973), Friedman and Long (1976), Skinner (1983), and MacLeod et al. (1995).

Prehistoric Use: The rapid and widespread prehistoric use of Newberry Volcano obsidian in the period following the eruption of the flows is well documented in central and northcentral Oregon (Skinner 1995a). Glass from this source is also occasionally encountered at sites in the Western Cascades, southwest Oregon, northwest Oregon, and Washington, and has been reported from as far north as British Columbia, Canada (Carlson 1994; Skinner and Winkler 1991, 1994; Skinner 1995; Musil and O'Neill 1997). The prehistory of the caldera area in general is described by Flenniken and Ozbun (1988) and Connolly (1999).

The trend surface model above depicts the geographic pattern of prehistoric use of Newberry Volcano obsidian. Click here to visit the State Museum of Anthropology's description of their archaeological research in Newberry Caldera in 1990-1992 and to see the rest of the contour map.

Obsidian Hydration: All flows are post-Mazama in age; maximum hydration rim measurements of artifacts correlated with the Newberry Volcano source group are approximately 5.2 - 5.3 microns (Skinner 1995b). A hydration rate of 2.9 µm²/1000 yrs is reported by Friedman (1977) and another rate of 3.0 µm²/1000 yrs is reported by Friedman and Obradovich (1981). Different caldera rates of 2.2 µm²/1000 yrs and 1.5 µm²/1000 yrs for different contexts are reported by Connolly and Byram (1999).