LATE HOLOCENE ISLAND VOLCANISM AT MONO LAKE, CALIFORNIA

Recent renewed interest among Earth scientists in the volcanism, tectonism, and paleoclimate of California's Mono Basin leads me to this review of the eruptive history of the volcanic Mono Islands, comprising Paoha Island, Negit Island, and the Negit Islets (among them "Java," "Twain," and "Little Norway"). While the relative youth of these features (all or nearly all of them apparently < 2,000 years old) has stifled attempts to directly date them, their ages can be constrained based on the presence/absence of dated tephras from the nearby Mono Craters and Domes; on the presence/absence of dated strandlines formed during past climate-induced fluctuations of Mono Lake; on the presence, on some features, of ancient rooted remaains of trees that grew low on island flanks during an extreme lake regression associated with the Medieval Climatic Anomaly; and on the presence of island ejecta in radiocarbon-dated stratigraphic sequences. At least two islands--Java and the Negit core--existed prior to ~1700 cal BP; at least one additional eruption, creating the lowest of the three Negit domes, occurred prior to ~1400 cal BP. A minimum of four eruptions took place between ~1400 and ~600 cal BP, and two more between ~600 and ~300 cal BP. The largest island in the lake, Paoha, is also the youngest, having been uplifted from the lake floor between C.E. ~1650 and ~1700; cinder cones and a small lava flow formed on the north end of the island after the uplift, and perhaps as late as the CE 1850s.