Volcano Hazards Program

Santiago, Chile

Volcano Hazards Program

Santiago, Chile
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McGee L.E.,University of Los Andes, Chile | McGee L.E.,University of Chile | McGee L.E.,Macquarie University | Brahm R.,University of Los Andes, Chile | And 13 more authors.
Contributions to Mineralogy and Petrology | Year: 2017

Small eruptive centres (SECs) representing short-lived, isolated eruptions are effective samples of mantle heterogeneity over a given area, as they are generally of basaltic composition and show evidence of little magmatic processing. This is particularly powerful in volcanic arcs where the original melting process generating stratovolcanoes is often obscured by additions from the down-going slab (fluids and sediments) and the overlying crust. The Pucón area of southern Chile contains active and dormant stratovolcanoes, Holocene, basaltic SECs and an arc-scale strike-slip fault (the Liquiñe Ofqui Fault System: LOFS). The SECs show unexpected compositional heterogeneity considering their spatial proximity. We present a detailed study of these SECs combining whole rock major and trace element concentrations, U-Th isotopes and olivine-hosted melt inclusion major element and volatile contents to highlight the complex inter-relations in this small but active area. We show that heterogeneity preserved at individual SECs relates to different processes: some start in the melting region with the input of slab-derived fluids, whilst others occur later in a centre’s magmatic history with the influence of crustal contamination prior to olivine crystallisation. These signals are deduced through the combination of the different geochemical tools used in this study. We show that there is no correlation between composition and distance from the arc front, whilst the local tectonic regime has an effect on melt composition: SECs aligned along the LOFS have either equilibrium U-Th ratios or small Th-excesses instead of the large—fluid influenced—U-excesses displayed by SECs situated away from this feature. One of the SECs is modelled as being generated from fluid-enriched depleted mantle, a source which it may share with the stratovolcano Villarrica, whilst another SEC with abundant evidence of crustal contamination may share its plumbing system with its neighbouring stratovolcano Quetrupillán, showing that polygenetic–monogenetic connections are unpredictable. Such marked preservation of individual magmatic histories highlights the isolation of individual melting events even in complex and highly volcanically active areas. © 2017, Springer-Verlag Berlin Heidelberg.


Reyes J.,University of Chile | Reyes J.,University of Los Andes, Chile | Lara L.E.,Volcano Hazards Program | Morata D.,University of Chile | Morata D.,University of Los Andes, Chile
Journal of Volcanology and Geothermal Research | Year: 2017

A remarkable expression of intraplate volcanism is the occurrence of evolutionary stages with important variations of magmatic processes and products. Plumbing systems and storage conditions seem to be different for shield and rejuvenated volcanism, two classical stages notably preserved in Robinson Crusoe Island, Juan Fernández Ridge in the SE Pacific Ocean. We here present first order geochemical features for rocks from both shield and rejuvenated stages and through geothermobarometry and textural analysis we unravel their contrasting ascent and storage history. The shield stage (~. 3.8. Ma) is represented by a ~. 900. m thick sequence of basalt, picrobasalt and picrite lava flows forming subsets according their chemistry and mineralogy: 'differentiated', 'near-primitive' and 'olivine-rich' lavas. Pressure estimates for in equilibrium assemblages are <. 3.2. kbar, and temperature ranges around 1321. °C for the 'near-primitive' and 1156-1181. °C for the 'differentiated' groups. Volcanic rocks from the rejuvenated stage (~. 0.9. Ma) fill the eroded morphology of the shield pile with basanite and picrite lava flows with two compositional varieties: the primitive 'high-Mg' group that crystallized clinopyroxene at pressures <. 3.7. kbar and olivine at temperatures in the range 1316-1354. °C; and the 'low-Mg' group that carries notably zoned crystals formed at a wide range of pressures (0-10.8. kbar) and temperatures (1256-1295. °C). This allows us to infer contrasting patterns of ascent and storage during these archetypical stages in Robinson Crusoe Island, which also controlled volcanic processes on surface and finally shaped the island. We propose the existence of shallow magmatic reservoirs in the shield stage, where the ascending magmas would have been stored and differentiated. On the other hand, rejuvenated magmas experimented rapid ascent with polybaric crystallization and sometimes short-time storage in low-volume reservoirs. Similar conditions have been proposed in other oceanic islands suggesting that shallow reservoirs in the shield stage and deeper crystallization of more alkaline magmas in the rejuvenated stage seems to describe a global pattern. © 2017 Elsevier B.V.


Lopez T.,University of Alaska Fairbanks | Lopez T.,Alaska Volcano Observatory | Thomas H.E.,Nicarnica Aviation | Prata A.J.,Nicarnica Aviation | And 4 more authors.
Journal of Volcanology and Geothermal Research | Year: 2015

Measurements of volcanic emissions (ash and SO2) from small-sized eruptions at three geographically dispersed volcanoes are presented from a novel, multichannel, uncooled imaging infrared camera. Infrared instruments and cameras have been used previously at volcanoes to study lava bodies and to assess plume dynamics using high temperature sources. Here we use spectrally resolved narrowband (~0.5-1μm bandwidth) imagery to retrieve SO2 and ash slant column densities (gm-2) and emission rates or fluxes from infrared thermal imagery at close to ambient atmospheric temperatures. The relatively fast sampling (0.1-0.5Hz) of the multispectral imagery and the fast sampling (~1Hz) of single channel temperature data permit analysis of some aspects of plume dynamics. Estimations of SO2 and ash mass fluxes, and total slant column densities of SO2 and fine ash in individual small explosions from Stromboli (Italy) and Karymsky (Russia), and total SO2 slant column densities and fluxes from Láscar (Chile) volcanoes, are provided. We evaluate the temporal evolution of fine ash particle sizes in ash-rich explosions at Stromboli and Karymsky and use these observations to infer the presence of at least two distinct fine ash modes, with mean radii of <10μm and >10μm. The camera and techniques detailed here provide a tool to quickly and remotely estimate fluxes of fine ash and SO2 gas and characterize eruption size. © 2015 Elsevier B.V.


Lopez T.,University of Alaska Fairbanks | Thomas H.E.,Nicarnica Aviation | Prata A.J.,Nicarnica Aviation | Amigo A.,Volcano Hazards Program | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2015

Measurements of volcanic emissions (ash and SO2) from small-sized eruptions at three geographically dispersed volcanoes are presented from a novel, multichannel, uncooled imaging infrared camera. Infrared instruments and cameras have been used previously at volcanoes to study lava bodies and to assess plume dynamics using high temperature sources. Here we use spectrally resolved narrowband (~0.5-1μm bandwidth) imagery to retrieve SO2 and ash slant column densities (gm-2) and emission rates or fluxes from infrared thermal imagery at close to ambient atmospheric temperatures. The relatively fast sampling (0.1-0.5Hz) of the multispectral imagery and the fast sampling (~1Hz) of single channel temperature data permit analysis of some aspects of plume dynamics. Estimations of SO2 and ash mass fluxes, and total slant column densities of SO2 and fine ash in individual small explosions from Stromboli (Italy) and Karymsky (Russia), and total SO2 slant column densities and fluxes from Láscar (Chile) volcanoes, are provided. We evaluate the temporal evolution of fine ash particle sizes in ash-rich explosions at Stromboli and Karymsky and use these observations to infer the presence of at least two distinct fine ash modes, with mean radii of <10μm and >10μm. The camera and techniques detailed here provide a tool to quickly and remotely estimate fluxes of fine ash and SO2 gas and characterize eruption size. © 2015 Elsevier B.V.


Pritchard M.E.,Cornell University | Henderson S.T.,Cornell University | Jay J.A.,Cornell University | Soler V.,CSIC - Institute of Natural Products and Agrobiology | And 12 more authors.
Journal of Volcanology and Geothermal Research | Year: 2014

We record non-eruptive background seismicity at eight potentially active volcanoes and one geothermal area in Chile and Bolivia for the first time in order to set a baseline for future episodes of unrest. We also compare seismicity to coincident new regional observations of ground deformation from InSAR and satellite observed thermal anomalies from the ASTER instrument. We deploy small temporary seismometer networks (1 to 5 stations each) of short and intermediate period instruments for 3-27. months at the nine areas between the years 2004 and 2012 at: Parinacota, Guallatiri, Isluga, Irruputuncu, Olca-Paruma, Ollagüe, Sol de Mañana, Putana, and Láscar. Despite the lack of shallow earthquakes in the global catalogs at these volcanoes, we find that all have volcano-tectonic events with at least 27 earthquake swarms - the most active are Putana, Guallatiri and Ollagüe. We find two examples where changes in seismicity are likely related to either deformation (in 2009 at Putana) or an increase in temperature (in 2012 at Isluga). Further, we document for the first time ground deformation at a Pliocene volcano called Sillajhuay, located in the Holocene volcano gap (i.e., 70. km from the nearest active volcano Isluga). We find that the four deforming volcanoes between 18 and 24°S are seismically active, but that seismic activity does not imply measurable ground deformation. Similarly, the seismically active volcanoes have satellite thermal hotspots, but there is no correlation between relative amounts of seismic activity and hotspot temperature. Because several of the volcanoes show variations in seismic activity, temperature, and deformation over the course of a few years unrelated to eruptions, decadal and longer observations are needed to constrain background activity in the central Andes. © 2014 Elsevier B.V.


Sepulveda P.,University of Chile | Le Roux J.P.,University of Chile | Le Roux J.P.,University of Los Andes, Chile | Lara L.E.,Volcano Hazards Program | And 3 more authors.
Biogeosciences | Year: 2015

Hotspot oceanic islands typically experience subsidence due to several processes related to migration of the oceanic plate away from the mantle plume and surface flexural loading. However, many other processes can interrupt subsidence, some of which may be associated with catastrophic events. A study of the biostratigraphy and sedimentology of Holocene deposits on Robinson Crusoe Island (RCI) on the Juan Fernández Ridge (JFR) indicated that dramatic uplift has occurred since 8000 years BP, at a rate of about 8.5mm yr-1. This is evidenced by supratidal flats with tepee structures and sand layers containing marine gastropods (mostly Nerita sp.) that are now exposed ca. 70 m a.s.l. The active hotspot is located 280 km further west and the last volcanic activity on RCI occurred at ca. 800 000 years BP. Long-term subsidence is evidenced by deep submerged marine abrasion terraces at RCI. As no direct evidence was found for the existence of a compensating bulge generated by the present hotspot upon which RCI would be situated, it must be concluded that subsidence in the wake of the mantle plume beneath the migrating plate was interrupted by very rapid uplift, but on a scale that did not fully compensate for the previous subsidence. This can be attributed to large-scale landslides followed by isostatic rebound, although this is only vaguely reflected in the low-resolution bathymetry of the area. To determine if this mechanism produced the uplift, a detailed bathymetric survey of the area will be required. If such a survey confirms this hypothesis, it may have implications for the short-term dynamics of vertical variations of oceanic edifices and their related effects on ecosystems and human population. © Author(s) 2015.


News Article | February 16, 2017
Site: www.wired.com

Earlier this month, Senator Lisa Murkowski of Alaska and Maria Cantwell of Washington introduced a bill to establish a National Volcano Early Warning and Monitoring System. Now, this isn’t the first time the senators have have attempted to establish a system to coordinate and update the monitoring of the United States’ many volcanoes, but it is a very timely bill. In December, the Bogoslof volcano in Alaska unexpectedly produced a violent explosive eruption—and continues to release occasional blasts that reach over 10 kilometers above the volcano. Explosions like that in the Aleutians can be a hazard for air and sea traffic in the area, but if such eruptions happened in the Cascades or Yellowstone, you could imagine the hazards. Bogoslof is mostly off the grid when it comes to volcano monitoring. It has no seismometers, no webcams, no real surveillance. Even now, after almost two months of eruptions, the Alaska Volcano Observatory relies on data from seismometers on other islands, reports from pilots and local residents, and remote sensing data from weather satellites to tell what’s happening at Bogoslof. This is far from ideal when you’re trying to keep people and property safe. Ideally, seismometers and other instruments at the volcano would measure the small changes in volcanic tremor that can give the first hints of an eruption in the next days to minutes. Now, you could argue that Bogoslof is in the middle of nowhere (and it is), so nobody should be surprised that it doesn’t have an array of instruments to measure its every move. There are hundreds of active or potentially active volcanoes in the Aleutians, so keeping a close watch on all of the is far beyond AVO’s capabilities. However, let’s consider another volcano: Glacier Peak in Washington State. Glacier Peak sits less than 125 kilometers from some major towns and cities, including Seattle, Everett, and Bellingham. It feeds rivers that drain into valleys where people live and work. It is by no means in the middle of nowhere. Over its history, it has produced some of the largest explosive eruptions in the Cascades over the last 25,000 years. It likely erupted last only a few hundred years ago. In all, it can be seen as a major potential volcanic hazard for the Pacific Northwest. So, how many seismometers watch this sleeping volcano? Right now: one. The single seismometer keeping vigil on Glacier Peak is a bit of a blunt instrument. Although it can detect shaking, you need at least a few seismometers to precisely locate the depth of earthquakes and tremors, especially if the seismicity is low. Most earthquakes associated with magma moving under a volcano, especially early on, are not big—lower than magnitude 2, so small that most people wouldn’t even feel any shaking. One lonely seismometer might be able to tell us that shaking is happening, but it would be difficult to deduce the style of shaking (important to tell if it is magma-related) or the depth of shaking (and even the exact geographic location over the shaking). This is why Senator Murkowski wants to enhance and modernize the country’s volcano monitoring. While Bogoslof’s eruption can be ignored to some degree, eruptions at places like Glacier Peak could pose major risks to life and property. Although the US Geological Survey Volcano Hazards Program could deploy temporary instruments, that reactive system could miss significant signs that permanent installations would have caught. It won’t be easy to get something like a National Volcano Early Warning and Monitoring System set up. The lower 48 states haven’t experienced an eruption since 2008, and the last major eruption was in 1980—both at Mount St. Helens. It’s easy to ignore the threat of eruptions when they happen so infrequently. But almost every western state has potentially active volcanoes. Monitoring the Salton Sea in California or Craters of the Moon in Idaho could be vital for protecting people both near and far from the eruption.


Lara L.E.,Volcano Hazards Program | Orozco G.,Volcano Hazards Program | Pina-Gauthier M.,Compania Minera Las Cenizas
Tectonophysics | Year: 2012

On January 19th 1835 a strong Strombolian flank eruption at Osorno (41.1°S) volcano was observed by Ch. Darwin, who was at the Chiloé Island at that time. One month later, a large M 8.5 thrust earthquake took place in central Chile with an epicentral area located ca. 480. km far away from Osorno volcano and a rupture zone that extended from ca. 35°S to 39°S, fairly similar to rupture zone of the Maule 2010 Mw 8.8 earthquake for what is the predecessor. Despite the dates, both have been considered as a typical earthquake-eruption pair and a case-study of remote tectonic triggering. In order to distinguish between remote and local (intraarc) tectonic control we perform a structural analysis of the 1835 fissure vents and cone alignments comparing the resulting geometry with that expected from both the active regional transpression along the arc and the coseismic strain pattern related with such a remote megathrust earthquake.Although the cone loading effect cannot be neglected, the asymmetric pattern of fissures and cone alignments with a prevailing NE-striking SHmax suggest a dominant arc tectonics control. In turn, volumetric expansion modeled with the inferred remote earthquake parameters is minimal at the Osorno volcano. Thus, the 1835 thrust earthquake would have not had a direct effect on the magma ascent and the final eruptive morphology. This case-study could serve as a threshold for the expected remote triggering related with megathrust earthquakes in the Andean subduction zone where statistically based models suggest possible effects even up to 700. km from the epicentral area. © 2011 Elsevier B.V.

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