Time filter

Source Type

Merced, Chile

Fontijn K.,University of Oxford | Fontijn K.,Ghent University | Rawson H.,University of Oxford | Van Daele M.,Ghent University | And 10 more authors.
Quaternary Science Reviews | Year: 2016

Well-characterised tephra horizons deposited in various sedimentary environments provide a means of synchronising sedimentary archives. The use of tephra as a chronological tool is however still widely underutilised in southern Chile and Argentina. In this study we develop a postglacial tephrochronological model for the Chilean Lake District (ca. 38 to 42°S) by integrating terrestrial and lacustrine records. Tephra deposits preserved in lake sediments record discrete events even if they do not correspond to primary fallout. By combining terrestrial with lacustrine records we obtain the most complete tephrostratigraphic record for the area to date. We present glass geochemical and chronological data for key marker horizons that may be used to synchronise sedimentary archives used for palaeoenvironmental, palaeoclimatological and palaeoseismological purposes. Most volcanoes in the studied segment of the Southern Volcanic Zone, between Llaima and Calbuco, have produced at least one regional marker deposit resulting from a large explosive eruption (magnitude ≥ 4), some of which now have a significantly improved age estimate (e.g., the 10.5 ka Llaima Pumice eruption from Llaima volcano). Others, including several units from Puyehue-Cordón Caulle, are newly described here. We also find tephra related to the Cha1 eruption from Chaitén volcano in lake sediments up to 400 km north from source. Several clear marker horizons are now identified that should help refine age model reconstructions for various sedimentary archives. Our chronological model suggests three distinct phases of eruptive activity impacting the area, with an early-to-mid-Holocene period of relative quiescence. Extending our tephrochronological framework further south into Patagonia will allow a more detailed evaluation of the controls on the occurrence and magnitude of explosive eruptions throughout the postglacial. © 2016 Elsevier Ltd. Source

Pallister J.S.,U.S. Geological Survey | Major J.J.,U.S. Geological Survey | Pierson T.C.,U.S. Geological Survey | Hoblitt R.P.,U.S. Geological Survey | And 11 more authors.
Eos | Year: 2010

High-silica rhyolite magma fuels Earth's largest and most explosive eruptions. Recurrence intervals for such highly explosive eruptions are in the 100- to 100,000year time range, and there have been few direct observations of such eruptions and their immediate impacts. Consequently, there was keen interest within the volcanology community when the first large eruption of high-silica rhyolite since that of Alaska's Novarupta volcano in 1912 began on 1 May 2008 at Chaitn volcano, southern Chile, a 3-kilometerdiameter caldera volcano with a prehistoric record of rhyolite eruptions [Naranjo and Stern, 2004; Servicio Nacional de Geologa y Minera (SERNAGEOMIN), 2008; Carn et al., 2009; Castro and Dingwell, 2009; Lara, 2009; Muoz et al., 2009]. Vigorous explosions occurred through 8 May 2008, after which explosive activity waned and a new lava dome was extruded. Source

Stebel K.,Norwegian Institute For Air Research | Amigo A.,SERNAGEOMIN | Thomas H.,Nicarnica Aviation AS | Prata A.J.,Nicarnica Aviation AS
Journal of Volcanology and Geothermal Research | Year: 2015

Putana is a stratovolcano in the central Andes volcanic zone in northern Chile on the border with Bolivia. Fumarolic activiy has been visible at its summit crater at 5890m altitude from long distances since the early 1800s. However, due to its remote location neither detailed geological studies have been made nor gas fluxes have been monitored and therefore its evolution remains unknown. On November 28, 2012 an ultraviolet (UV) imaging camera was transported to Putana and for about 30min images of the fumaroles were recorded at 12Hz. These observations provide the first measurements of SO2 fluxes from the fumarolic field of Putana and demonstrate the applicability of the UV camera to detect such emissions. The measurement series was used to assess whether the sampling rate of the data influences the estimate of the gas flux. The results suggest that measurements made at 10s and 1min intervals capture the inherent (turbulent) variability in both the plume/wind speed and SO2 flux. Relatively high SO2 fluxes varying between 0.3kgs-1 and 1.4kgs-1, which translates to 26t/day and 121t/day assuming constant degassing throughout the day, were observed on November 28, 2012. Furthermore, we demonstrate how an optical flow algorithm can be integrated with the SO2 retrieval to calculate SO2 fluxes at pixel level. Average values of 0.64kgs-1±0.20kgs-1 and 0.70kgs-1±0.53kgs-1 were retrieved from a "classical" transect method and the "advanced" optical flow based retrieval, respectively. Assuming constant emissions throughout all times, these values would results in an average annual SO2 burden of 20-22 kT. © 2015. Source

Discover hidden collaborations