Series Of Eruptions Research Articles

Relationship of pyroclastic volcanism and lake-water acidification to Jehol Biota mass mortality events (Early Cretaceous, northeastern China)

Geochemical analysis of the 14.4-m-thick lacustrine succession of the Lower Cretaceous Yixian Formation (Jehol Group) has yielded new insights concerning vertebrate mass mortality events in the Lake Sihetun volcanic caldera in western Liaoning Province (northeastern China) that produced the Jehol Biota fossil lagerstätten. The long-term evolution of the caldera system resulted in a shift from felsic to mafic magma chemistry, accompanied by a reduced frequency of pyroclastic eruptions, declining hydrothermal activity, and lower lacustrine productivity. The basal Tetrapod Beds exhibit strong hydrothermal influence, as indicated by enrichments of boron (B), certain alkalis (Rb, Cs), rare-earth elements (REEs), yttrium (Y), and many metals (e.g., Co, Cr, Cu, Ge, Mo, Ni, Sb, U, V, and W), and by strongly negative molybdenum isotope compositions (δ98Mo to –2.50‰) that may record large fractionations between molybdate and thiomolybdate species in the Sihetun caldera hydrothermal system. In contrast, the overlying Fish Beds and Non-Fossiliferous Beds have an elemental and Mo-isotopic composition similar to calc-alkaline basalts (δ98Mo=–0.29±0.04‰) in the surrounding watershed, suggesting weathering of Yixian Formation volcanic rocks as the major source of sediment. During its <700-kyr-long history, Lake Sihetun was affected by four environmental cycles, each commencing with a series of pyroclastic eruptions that triggered systematic changes in lakewater chemistry. Following each eruption interval, enhanced weathering of volcanic ash in the surrounding watershed caused lakewater pH to decrease and lacustrine productivity to increase. Continued weathering of bases from basement volcanic rocks subsequently produced alkaline conditions in the lake, leading to precipitation of authigenic carbonate layers and lower lacustrine productivity. Analysis of geochemical redox proxies strongly suggests that the Lake Sihetun water column was completely oxic, in contrast to earlier inferences of a stratified anoxic water column, and that ubiquitous lamination in the lacustrine succession was due to other factors such as widespread microbial mats and/or rapid sediment deposition.

Geohazards (floods and landslides) in the Ndop plain, Cameroon volcanic line

AbstractThe Ndop Plain, located along the Cameroon Volcanic Line (CVL), is a volcano-tectonic plain, formed by a series of tectonic movements, volcanic eruptions and sedimentation phases. Floods (annually) and landslides (occasionally) occur with devastating environmental effects. However, this plain attracts a lot of inhabitants owing to its fertile alluvial soils. With demographic explosion in the plain, the inhabitants (143,000 people) tend to farm and inhabit new zones which are prone to these geohazards. In this paper, we use field observations, laboratory analyses, satellite imagery and complementary methods using appropriate software to establish hazard (flood and landslide) maps of the Ndop Plain. Natural factors as well as anthropogenic factors are considered.The hazard maps revealed that 25% of the area is exposed to flood hazard (13% exposed to high flood hazard, 12% to moderate) and 5% of the area is exposed to landslide hazard (2% exposed to high landslide hazard, 3% to moderate). Some mitigation measures for floods (building of artificial levees, raising foundations of buildings and the meticulous regulation of the flood guards at Bamendjing Dam) and landslides (slope terracing, planting of trees, and building retaining walls) are proposed.

Certain Results of Measurements of Characteristics of Stratospheric Aerosol Layer and Total Ozone Content at Siberian Lidar Station in Tomsk

We consider the results of long-term remote optical monitoring, obtained at the Siberian Lidar Station of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences in Tomsk (56.5°N, 85.0°E). The scattering characteristics of stratospheric aerosol layer, obtained according to data of lidar measurements since 1986, are presented. We analyze the trends of changes in the total ozone (TO) content over Tomsk for the period 1996-2013 according to data of spectrophotometric measurements with employment of Total Ozone Mapping Spectrometer (TOMS) data for the period 1979-1994. We determined the periods of elevated content of stratospheric aerosol over Tomsk aftera series of explosive eruptions of volcanoes of Pacific Ring of Fire and Iceland in 2006-2011. Since the second half of 1990s, we record an increasing TO trend, equaling 0.65 DU/yr for the period 1996-2013.

Improved stratospheric aerosol extinction profiles from SCIAMACHY: validation and sample results

Abstract. Stratospheric aerosol extinction profiles have been retrieved from SCIAMACHY/Envisat measurements of limb-scattered solar radiation. The retrieval is an improved version of an algorithm presented earlier. The retrieved aerosol extinction profiles are compared to co-located aerosol profile measurements from the SAGE II solar occultation instrument at a wavelength of 525 nm. Comparisons were carried out with two versions of the SAGE II data set (version 6.2 and the new version 7.0). In a global average sense the SCIAMACHY and the SAGE II version 7.0 extinction profiles agree to within about 10 % for altitudes above 15 km. Larger relative differences (up to 40 %) are observed at specific latitudes and altitudes. We also find differences between the two SAGE II data versions of up to 40 % for specific latitudes and altitudes, consistent with earlier reports. Sample results on the latitudinal and temporal variability of stratospheric aerosol extinction and optical depth during the SCIAMACHY mission period are presented. The results confirm earlier reports that a series of volcanic eruptions is responsible for the increase in stratospheric aerosol optical depth from 2002 to 2012. Above about an altitude of 28 km, volcanic eruptions are found to have negligible impact in the period 2002–2012.

Dental Eruption Series and Replacement Pattern in Miocene Prosantorhinus (Rhinocerotidae) as Revealed by Macroscopy and X-ray: Implications for Ontogeny and Mortality Profile

Fossil evidence of complete sequences of dental ontogeny in extinct mammals is rare but contains valuable information on the animal’s physiology, life history, and individual age. Here, we analyzed an exceptionally high number of juvenile dentaries at different developmental stages including highly fragile tooth germs of the extinct rhinoceros Prosantorhinus germanicus from the Miocene fossil lagerstatte Sandelzhausen in Germany. We used dental wear stages, eruption stages, and tooth germ development in order to reconstruct the tooth replacement pattern for P. germanicus. The results allow for the distinction of 11 dental eruption stages and document a tooth eruption sequence of (d2, d3), (d1, d4), m1, m2, p2, p3, p4, m3; a pattern identical to that reported for the extant African rhinoceros, Diceros bicornis. Moreover, our findings indicate that P. germanicus falls into the life history category of slow-growing, long-living mammals. The dental eruption stages of the fossil rhinoceros were correlated with data of living rhinoceroses in order to gain insight into the age-at-death distribution of P. germanicus at Sandelzhausen. The juvenile mortality profile of P. germanicus shows a trend of selective mortality at an inferred age range of about 3 months to 3 years. As this age range represents a life phase of increased natural risk of mortality, our findings indicate a gradual accumulation of corpses (attritional fossil assemblage). This result supports the interpretation of a taphocenosis found at the Sandelzhausen fossil site.

Undeveloped high-enthalpy geothermal fields of the Taupo Volcanic Zone, New Zealand

In the Taupo Volcanic Zone there are 21 high enthalpy (>225°C) geothermal fields with 7 utilised for power generation. This paper presents an overview of the undeveloped high enthalpy geothermal systems of the region; namely, Rotoma—Tikorangi, Tikitere, Taheke, Rotomahana—Waimangu, Waiotapu (including Waikite), Reporoa, Te Kopia, Orakei Korako, Mangakino, Horomatangi, Tokaanu—Waihi and Tongariro. Most of these geothermal systems are hosted in rocks of rhyolitic composition, although Tokaanu—Waihi and Tongariro are hosted in andesitic rocks. Some of the geothermal systems have extensive surface thermal manifestations (e.g. Waiotapu, 17km2), whereas others have few (e.g. Rotoma—Tikorangi), largely reflecting limited hydrological connectivity to the surface (i.e. impermeable rocks, structures). Uniquely, Horomatangi is fully submerged beneath Lake Taupo. All have liquid-dominated reservoirs of neutral pH alkali chloride waters, except for Tongariro which is inferred to have a vapour-dominated reservoir.Volcanic and tectonic activity, both past and present has impacted the near surface hydrology of geothermal systems in the Taupo Volcanic Zone. For example, the 1886 volcanic eruption of Mount Tarawera resulted in a series of phreatomagmatic and hydrothermal eruptions through the Rotomahana geothermal system, and created new fluid flow pathways and established thermal features at Waimangu Valley. Similarly, tectonic activity with movement along the Paeroa Fault has disturbed the Te Kopia geothermal field by changing the hydrology and resulted in the juxtaposition of acid on neutral alteration minerals in the upthrown fault block. But despite these volcanic and fault interruptions, thermal activity has continued. Several systems show evidence of thermal decline (Mangakino, Orakei Korako, Te Kopia), and the occurrence of altered ground and relict sinter between Te Kopia and Orakei Korako suggest they may at one time have been been hydrologically connected in the near surface.

The evolution of hydrous magmas in the Tongariro Volcanic Centre: the 10 ka Pahoka-Mangamate eruptions

The majority of arc-type andesites in the Tongariro Volcanic Centre are highly porphyritic, hornblende-free, two-pyroxene andesites. An exception is tephras from the c. 10,000 ka Pahoka-Mangamate event. Magmas of these Plinian eruptions bypassed the extensive crustal mush columns under the central volcanoes and sequentially derived a series of almost aphyric rocks spanning a compositional range from dacite to basaltic andesite. Mineral composition, trace element and isotopic data suggest that this eruptive series tapped a mid-crustal magma reservoir, resulting in the initial eruption of an hydrous dacitic magma and several following eruptions characterised by less-evolved and less-hydrous compositions at progressively higher temperatures and substantially lower 87Sr/86Sr ratios. Systematic changes in magma chemistry are also reflected in a sequential change in phenocryst content starting with an early hornblende–plagioclase-dominated assemblage to a late olivine–plagioclase-dominated assemblage.

Efforts to conserve endangered terrestrial orchids in situ and ex situ at two natural reserves within Central Mexico

The natural vegetation in and around Mexico City once harbored an unusually high number of plant and animal (insect) species, including endemics (Vázquez 1973, Ceballos &amp; Galindo 1984, Rzedowski 1991). The high diversity in this region has been attributed to the unusual topography resulting from a series of volcanic eruptions that ended ca. 1800 years ago (Siebe et al. 2004). In addition, two phyto-geographic regions overlap within Central Mexico that support diverse vegetation types (e.g., shrubs, mature pine forests).

Optical monitoring of characteristics of the stratospheric aerosol layer and total ozone content at the Siberian Lidar Station (Tomsk: 56° 30′ N; 85° E)

We consider the results of long-term remote optical monitoring obtained at the Siberian Lidar Station of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (56° 30′ N, 85° E). The scattering characteristics of stratospheric aerosol layer, obtained according to data of lidar measurements recorded since 1986, are presented. We analyse the trends of changes in the total ozone (TO) content over Tomsk for the period 1996–2013 according to data of spectrophotometric measurements employing Total Ozone Mapping Spectrometer (TOMS) data for the period 1979–1994. We determined the periods of elevated content of stratospheric aerosol over Tomsk after a series of explosive eruptions of volcanoes in the Pacific Ring of Fire and Iceland in 2006–2011. Since the second half of the 1990s we have recorded an increasing TO trend, equalling 0.65 DU/year for the period 1996–2013.

Temporal variations in fumarole gas chemistry at Poás volcano, Costa Rica

We report the chemical and isotopic composition of fumarole gas discharges collected at Poás Volcano, Costa Rica from 2001 to 2014, covering a period during which the volcano experienced a series of phreatic eruptions (March 2006 to October 2014). The relative abundances of Poás C–S–H–O gas species are controlled by reactions involving the SO2–H2S and So–SO2 gas buffers indicating magmatic temperatures of up to 800°C. Although fumarole outlet temperatures are <120°C for most samples, SO2 is the dominant sulfur gas and HCl contents are relatively high. Gas compositional changes within the magma-lake-hydrothermal system likely result from a combination of several processes, including: 1) The injection of new and undegassed magma in late 2000–early 2001, 2) the heating of the hydrothermal system, accompanied by gas pressure build-up, and 3) hydrofracturing through 2006. These processes culminated in the phreatic eruptions of 2006 and 2008. Since 2005 the lake level has declined and is now (January 2014) at the lowest level (10m) since the last periods that it dried out completely (April 1984 and April 1994). The most recent data of 2014 show high level of degassing from the dome fumaroles and the release of HCl-rich and CO2-poor gases implies that the magma injected in late 2000 continues to supply volatiles. Our data show that time series sampling of fumarole gases provides important insights to better understand magmatic and hydrothermal processes at active volcanoes and also to potentially forecast phreatic eruptions.

From rain to ranges.

The article discusses geologists' study of rain to map the transformation of California's Sierra Nevada Mountains since the Oligocene period. Topics include the diffusion of rain into volcanic deposits caused by a series of volcanic eruptions, the study of hydrogen isotope ratios in rock samples by University of Idaho geologist Elizabeth Cassel and colleagues to determine peak elevations in Nevada, and the colliding of the North American and Pacific plates to form the San Andreas Fault.

Reassessing obsidian field relationships at Glass Buttes, Oregon

The Glass Buttes complex in the High Lava Plains of Oregon produced obsidians during a series of rhyolitic eruptions circa 5.8 to 6.5Ma. These obsidians have been used to craft stone tools for millennia, from Clovis peoples to modern knappers, and have been recovered at sites throughout the Pacific Northwest. Glass Buttes is also the origin of much obsidian used for lithic replication experiments and to test new techniques for sourcing. Paradoxically, the spatial distributions of chemically distinct obsidians at this complex have received comparatively little attention. The only published study to connect obsidian compositional differences to the Glass Buttes landscape is Ambroz et al. (2001), who reported seven discrete, spatially constrained obsidian “chemical groups” based on clustered data in elemental scatterplots. Since its publication, their paper has been cited as an example of successful obsidian “subsource” characterization. During the course of a wider research program, we collected 337 specimens at Glass Buttes from loci originally sampled by Ambroz et al. (2001). While we could replicate the “chemical groups” observed by Ambroz et al. (2001), we were unable to reproduce the reported spatial distribution of sources across the landscape. Almost half of the resampled loci exhibited intermingled populations of chemical types due to their locations on alluvial–colluvial deposits. We also identified five additional obsidian chemical types at the complex; however, geochemically significant elements suggest that only a subset of these eleven types correspond to different flows and domes at Glass Buttes. A few appear to reflect chemical zoning within flows, whereas two other types may be exogenous, moved from nearby obsidian sources via secondary transport. Thus, we demonstrate here that the discrete subsource zones demarcated by Ambroz et al. (2001) do not reflect reality on the landscape. This, in turn, alters how artifact sourcing results are interpreted with respect to how mobile foraging groups interacted with the landscape and made choices regarding resource acquisition, toolstone provisioning, and land use.

Volcanic hazard on Deception Island (South Shetland Islands, Antarctica)

Deception Island is the most active volcano in the South Shetland Islands and has been the scene of more than twenty identified eruptions over the past two centuries. In this contribution we present the first comprehensive long-term volcanic hazard assessment for this volcanic island. The research is based on the use of probabilistic methods and statistical techniques to estimate volcanic susceptibility, eruption recurrence and the most likely future eruptive scenarios. We perform a statistical analysis of the time series of past eruptions and the spatial extent of their products, including lava flows, fallout, pyroclastic density currents and lahars. The Bayesian event tree statistical method HASSET is applied to calculate eruption recurrence, while the QVAST tool is used in an analysis of past activity to calculate the possibility that new vents will open (volcanic susceptibility). On the basis of these calculations, we identify a number of significant scenarios using the GIS-based VORIS 2.0.1 and LAHARZ software and evaluate the potential extent of the main volcanic hazards to be expected on the island. This study represents a step forward in the evaluation of volcanic hazard on Deception Island and the results obtained are potentially useful for long-term emergency planning.

Geyser preplay and eruption in a laboratory model with a bubble trap

We present visual observations and temperature measurements from a laboratory model of a geyser. Our model incorporates a bubble trap, a zone in which vapor can accumulate in the geyser's subsurface plumbing, in a vertical conduit connected to a basal chamber. Analogous features have been identified at several natural geysers. We observe three types of eruptions: 1) rising bubbles eject a small volume of liquid in a weak spout (small eruption); 2) boiling occurs in the conduit above the bubble trap (medium eruption); and 3) boiling occurs in the conduit and chamber (large eruption). In the last two cases, boiling in the conduit causes a rapid hydrostatic pressure drop that allows for the rise and eruption of liquid water in a vigorous spout. Boiling initiates at depth rather than propagating downward from the surface. In a single eruption cycle, multiple small eruptions precede every medium and large eruption. At least one eruption cycle that culminates in a medium eruption (i.e., a quiescent period followed by a series of small eruptions leading up to a medium eruption) precedes every eruption cycle that culminates in a large eruption. We find that the transfer of fluid with high enthalpy to the upper conduit during small and medium eruptions is necessary to heat the upper conduit and prepare the system for the full boiling required for a large eruption. The placement of the bubble trap midway up the conduit allows for more efficient heating of the upper conduit. Our model provides insight into the influence of conduit geometry on eruption style and the importance of heat transfer by smaller events in preparing the geyser system for eruption.

Volcano-induced regime shifts in millennial tree-ring chronologies from northeastern North America.

Dated records of ice-cap growth from Arctic Canada recently suggested that a succession of strong volcanic eruptions forced an abrupt onset of the Little Ice Age between A.D. 1275 and 1300 [Miller GH, et al. (2012) Geophys Res Lett 39(2):L02708, 10.1029/2011GL050168]. Although this idea is supported by simulation experiments with general circulation models, additional support from field data are limited. In particular, the Northern Hemisphere network of temperature-sensitive millennial tree-ring chronologies, which principally comprises Eurasian sites, suggests that the strongest eruptions only caused cooling episodes lasting less than about 10 y. Here we present a new network of millennial tree-ring chronologies from the taiga of northeastern North America, which fills a wide gap in the network of the Northern Hemisphere's chronologies suitable for temperature reconstructions and supports the hypothesis that volcanoes triggered both the onset and the coldest episode of the Little Ice Age. Following the well-expressed Medieval Climate Anomaly (approximately A.D. 910-1257), which comprised the warmest decades of the last millennium, our tree-ring-based temperature reconstruction displays an abrupt regime shift toward lower average summer temperatures precisely coinciding with a series of 13th century eruptions centered around the 1257 Samalas event and closely preceding ice-cap expansion in Arctic Canada. Furthermore, the successive 1809 (unknown volcano) and 1815 (Tambora) eruptions triggered a subsequent shift to the coldest 40-y period of the last 1100 y. These results confirm that series of large eruptions may cause region-specific regime shifts in the climate system and that the climate of northeastern North America is especially sensitive to volcanic forcing.

Elizabeth F. Thompson. Justice Interrupted: The Struggle for Constitutional Government in the Middle East.

Middle Eastern events of recent years have left many observers perplexed. What have the protesting masses hoped to achieve, and what accounts for their short-term successes or failures? Many people were surprised by the emergence of protest movements in the Middle East and imagined them as a series of spontaneous eruptions. Western intelligence agencies were likewise caught unawares. But what about the people who live in in the region, or scholars of the area? Some of them were surprised, too, but Elizabeth F. Thompson would not have been among them. Thompson places her insightful new book squarely at the intersection of current events and the last couple of centuries of human history in the Middle East. In doing so she contributes meaningfully, and with originality, to contemporary and historical discussions about democracy and popular movements in the region. She argues that the peoples of the Middle East have sought justice and representation, variably understood and expressed over time, and that the account of their quest is a worthwhile and important universal human story. The book is a new “people's history” of the modern Middle East.

Drilling Into the Track of the Yellowstone Hot Spot

The Yellowstone supervolcano erupted roughly 640,000 years ago, covering much of North America in a thick coat of ash. Material ejected from the volcano devastated the surrounding area, and particles injected into the atmosphere changed the Earth's climate. Over the past 18 million years the Yellowstone hot spot has powered a series of similar eruptions. In southern Idaho, the 640‐kilometer‐long Snake River Plain traces the path of the Yellowstone hot spot over this period.

Regional odontodysplasia crossing the midline: A unique case associated with bilateral impacted supernumerary teeth

Regional odontodysplasia (RO) is an uncommon developmental anomaly affecting a localized area of dentition, with distinctive clinical, radiographic, and histological findings. It is presumed to be the result of a developmental disturbance that locally affects the odontogenic ectodermal and mesodermal tissues. In general, it is limited to only one arch and sometimes it can occasionally cross the midline. Supernumerary teeth (ST) are mammalian developmental abnormalities characterized by the presence of extra teeth in addition to the normal eruption series. Here, we report a case of RO that affected right maxillary teeth crossing the midline and showed two maxillary bilateral impacted ST.

Estimation of exit velocity of volcanic plume from analysis of vortex structures

We propose a simple method for estimating the exit velocities of volcanic eruptions from the observation of volcanic plumes. For this purpose, we used a model of a vortex ring of an experimental jet, which was developed in the engineering field. To validate the model for the vortex structures of volcanic plumes, we applied it to plumes generated in 3-D numerical simulations. In 11 cases where exit velocity (66.8–200.5 m/s) is given as a boundary condition, we successfully estimated it with 7% underestimation by analyzing the size and motion of the leading vortex ring that forms at the plume front. Using the same procedure, we could also estimate the exit velocity by analyzing the trailing vortices that develop behind the vortex ring (14% underestimation). From these results, we conclude that: (i) the model of the vortex ring proposed by the jet engineering studies is appropriate for the vortex ring at the front of simulated volcanic plumes, and (ii) the model is also applicable to the trailing vortices of the plumes. These conclusions indicate that we can estimate the time evolution of the exit velocity for a series of eruptions from observations of the vortex structures of the actual volcanic plumes. By applying that method to an eruption of Sakurajima volcano on February 15, 2011, we found that following an increase during the first 10 s of the eruption, the exit velocity remained constant at >40 m/s up to 80 s after the onset of the eruption. Our method will be useful in understanding the time evolution of eruptive events, such as the transitional behavior from stable column to column collapse, from observations of volcanic plumes.

Francis Alive and Aloft: Franciscan Apocalypticism in the Colonial Andes

The seventeenth century opened with a bang, literally. In the year 1600, on the first Friday in the season of Lent, sometime between noon and 3:00 PM (that is, at the hour of the accustomed Lenten penitential processions), the Peruvian volcano of Huaynapudna began a protracted series of explosions and eruptions. It was the largest recorded volcanic eruption in the Western Hemisphere, greater by far than that of Mount Vesuvius in 79 CE, or Mount St. Helens in 1980, and only slightly smaller than the colossal eruption of Krakatoa, Indonesia, in 1883. The event sent both Christian Spaniards and neo-Christian Indians searching for answers to apocalyptic questions. On that same Friday, February 18, 1600, several other violent earthquakes leveled buildings nearby.