Determining the Eruption Temperature of Io's Lava

Determination of eruption temperature of Io's lavas using lava tube skylights

Authors:

Davies et al

Abstract:

Determining the eruption temperature of Io's dominant silicate lavas would constrain Io's present interior state and composition. We have examined how eruption temperature can be estimated at lava tube skylights through synthesis of thermal emission from the incandescent lava flowing within the lava tube. Lava tube skylights should be present along Io's long-lived lava flow fields, and are attractive targets because of their temporal stability and the narrow range of near-eruption temperatures revealed through them. We conclude that these skylights are suitable and desirable targets (perhaps the very best targets) for the purposes of constraining eruption temperature, with a 0.9:0.7-µm radiant flux ratio ≤6.3 being diagnostic of ultramafic lava temperatures. Because the target skylights may be small – perhaps only a few m or 10 s of m across – such observations will require a future Io-dedicated mission that will obtain high spatial resolution ( < 100 m/pixel), unsaturated observations of Io's surface at multiple wavelengths in the visible and near-infrared, ideally at night. In contrast to observations of lava fountains or roiling lava lakes, where accurate determination of surface temperature distribution requires simultaneous or near-simultaneous ( < 0.1 s) observations at different wavelengths, skylight thermal emission data are superior for the purposes of temperature derivation, as emission is stable on much longer time scales (minutes, or longer), so long as viewing geometry does not greatly change during that time.

Evidence of a Supervolcano Eruption From Albian Cretaceous Australia

The answers are blowin' in the wind: Ultra-distal ashfall zircons, indicators of Cretaceous super-eruptions in eastern Gondwana

Authors:

Barham et al

Abstract:

An Early Cretaceous siliceous large igneous province (SLIP) that developed on the eastern margin of Gondwana produced some of the most voluminous siliceous volcaniclastic deposits known globally. We report U-Pb ages and trace-element and Hf-isotopic signatures of detrital zircons from the Madura Shelf (onshore Bight Basin), Western Australia. These zircons include a geochemically distinct 106 Ma component with age and Hf characteristics that match SLIP volcanics some 2300 km distant in eastern Australia. This young subpopulation shows limited grain abrasion, which contrasts with older detrital components that are stratigraphically persistent. Regional detrital zircon provenance demonstrates that sediment routing systems were disconnected in the eastern and western Bight Basin, negating terrestrial transport mechanisms as a possible vector of the zircons from the SLIP to their recovered position. Palynology indicates that the 106 Ma zircons are syn-depositional, and we interpret them as being significantly transported in an eruption plume. Given the grain size and distance from source, such distal zircon emplacement suggests previously undocumented 106 Ma super-eruptions. The 106 Ma zircons likely reflect Southern Hemisphere winter eruptions when tropospheric polar easterly winds would have been favored across southeastern Australia.

Mercury Increased in Three Different Spikes From Deccan Traps Across the K-T/K-Pg Boundary

Mercury enrichment and Hg isotopes in Cretaceous–Paleogene boundary successions: Links to volcanism and palaeoenvironmental impacts

Authors:

Sial et al

Abstract:

We investigate the use of Hg as a proxy for volcanism by studying four distal and two proximal sections in relation to the Deccan volcanic center, straddling the Cretaceous–Paleogene (KPg) boundary at (a) Højerup (Denmark), Bottaccione and Padriciano (Italy), (b) Meghalaya and Jhilmili (India), and (c) Bajada del Jagüel (Argentina). Hg sequestration by organic matter results in constant Hg/TOC ratio and linear correlation between Hg content of the sediments and total organic carbon (TOC).

Elevated Hg concentrations that deviate from this linear relationship represent most likely true Hg anomalies and these notable Hg/TOC spikes (all TOC <1 al="" also="" and="" are="" at="" between="" biozone="" bottaccione="" boundary="" cf2="" clear="" correlation="" foraminiferal="" found="" h="" hg="" i="" ii="" iii="" in="" jerup="" jhilmili="" kpg="" meghalaya="" no="" occurs="" p1a="" planktic="" section.="" sections="" spike="" sub="" subzone="" the="" within="">2

O₃ exists in any of the studied sections. The Hg anomalies probably result from strong volcanic episodes of the Deccan phase-2 (started 250 kyr before the KPg boundary and lasted for 750 kyr) that exhaled sulfuric aerosols, carbon dioxide and other toxic agents which reached a critical threshold, represented in true Hg enrichments in the paleoenvironments. The possibility that Hg enrichments resulted from anoxia scavenging on the seafloor and penetration downward into sediments is not supported in the stratigraphic record of Mo/Al ratios redox proxy.<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">

<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within=""> Hg isotopes were analyzed in samples from all KPg boundary sections in this study and from Bidart, France, the latter for comparison. Hg isotopes yielded δ202Hg values ranging from −1 to −2‰ and Δ201Hg signatures from 0 to 0.05‰ (spike II in Højerup, Bottaccione and Meghalaya KPg boundary layers) consistent with volcanic emission of Hg (0 to −2‰). The δ202Hg in spike I in Meghalaya and Padriciano and spike III in Jhilmili is consistent with volcanic emission of Hg. Two samples from Bajada del Jagüel and four from Bidart, however, display isotope signals compatible with volcanic emission/chondrite Hg. The results of three other samples are characteristic for reworked sediment, soil and/or peat. Most of the data show small positive Δ201Hg, in favor of long-term atmospheric transport prior to deposition, supporting a volcanic origin for the Hg. The present study broadens, therefore, the potential use of Hg as stratigraphic marker and, moreover, confirms that in the critical KPg transition, Hg was enriched in paleoenvironments at three distinct stages during the Deccan phase-2.
<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">

<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">

Simulating Europa's Water Plumes

DSMC simulation of Europa water vapor plumes

Authors:

Berg et al

Abstract:

A computational investigation of the physics of water vapor plumes on Europa was performed with a focus on characteristics relevant to observation and spacecraft mission operations. The direct simulation Monte Carlo (DSMC) method was used to model the plume expansion assuming a supersonic vent source. The structure of the plume was determined, including the number density, temperature, and velocity fields. The possibility of ice grain growth above the vent was considered and deemed probable for large (diameter > ∼20 m) vents at certain Mach numbers. Additionally, preexisting grains of three diameters (0.1, 1, 50 µm) were included and their trajectories examined. A preliminary study of photodissociation of H2O into OH and H was performed to demonstrate the behavior of daughter species. A set of vent parameters was evaluated including Mach number (Mach 2, 3, 5), reduced temperature as a proxy for flow energy loss to the region surrounding the vent, and mass flow rate. Plume behavior was relatively insensitive to these factors, with the notable exception of mass flow rate. With an assumed mass flow rate of ∼1000 kg/s, a canopy shock occurred and a maximum integrated line of sight column density of ∼1020 H2O molecules/m2 was calculated, comparing favorably with observation (Roth et al., 2014a).

Enceladus' Plumes Explained?

Sustained eruptions on Enceladus explained by turbulent dissipation in tiger stripes

Authors:

Kite et al

Abstract:

Spacecraft observations suggest that the plumes of Saturn's moon Enceladus draw water from a subsurface ocean, but the sustainability of conduits linking ocean and surface is not understood. Observations show sustained (though tidally modulated) fissure eruptions throughout each orbit, and since the 2005 discovery of the plumes. Peak plume flux lags peak tidal extension by ∼1 radian, suggestive of resonance. Here we show that a model of the tiger stripes as tidally-flexed slots that puncture the ice shell can simultaneously explain the persistence of the eruptions through the tidal cycle, the phase lag, and the total power output of the tiger stripe terrain, while suggesting that the eruptions are maintained over geological timescales. The delay associated with flushing and refilling of \emph{O}(1) m-wide slots with ocean water causes erupted flux to lag tidal forcing and helps to buttress slots against closure, while tidally pumped in-slot flow leads to heating and mechanical disruption that staves off slot freeze-out. Much narrower and much wider slots cannot be sustained. In the presence of long-lived slots, the 106-yr average power output of the tiger stripes is buffered by a feedback between ice melt-back and subsidence to \emph{O}(1010) W, which is similar to the observed power output, suggesting long-term stability. Turbulent dissipation makes testable predictions for the final flybys of Enceladus by the \emph{Cassini} spacecraft. Our model shows how open connections to an ocean can be reconciled with, and sustain, long-lived eruptions. Turbulent dissipation in long-lived slots helps maintain the ocean against freezing, maintains access by future Enceladus missions to ocean materials, and is plausibly the major energy source for tiger stripe activity.

How did the Southeast Maya Survive Volcanic Eruptions?

Across the centuries, forming cooperative networks beyond cultural boundaries has been a way to overcome natural disasters.

A Nagoya University researcher and his leading international research group discovered a Great Platform built with different kinds of stone at the archeological site of San Andrés, El Salvador, and challenged the prevailing theory regarding the sociocultural development of Southeastern Maya frontier.

San Andrés is located in the Zapotitan Valley, El Salvador, known as Southeastern Maya zone. Archaeological investigation conducted during 40's and 90's has shown that San Andrés had long human occupation beginning from the Middle Preclassic (ca. 600 BC) until the Early Postclassic (ca. AD 1200), in which had role as political, economic and religious center during the Late Classic period (AD 600-900). As San Andrés has been affected by numerous explosive eruptions -- at least three or four -- during the past two millennia, archaeologists have been interested to understand the role of volcanic eruptions in human history.

Between February and May of 2016, the research group led by Assistant Prof. Akira Ichikawa of the Institute for Advanced Research and at the Graduate School of Letters, Nagoya University, made a new discovery that allowed them to reconsider the recovery process from the volcanic eruption of Ilopango (ca. AD 400-450), which was one of the greatest Holocene eruptions in Central America. Assistant Prof. Ichikawa explained: "We have discovered a masonry platform just above the ash caused by the Ilopango eruption in San Andrés, which could prove that people reoccupied in such a devastated area even immediately after the enormous disaster occurred."

link.

Did two Volcanic Eruptions in 536 & 540 AD Change the Course of History?

Contemporary chroniclers wrote about a "mystery cloud" which dimmed the light of the sun above the Mediterranean in the years 536 and 537 CE. Tree rings testify poor growing conditions over the whole Northern Hemisphere - the years from 536 CE onward seem to have been overshadowed by an unusual natural phenomenon. Social crises including the first European plague pandemic beginning in 541, are associated with this phenomenon. Only recently have researchers found conclusive proof of a volcanic origin of the 536 solar dimming, based on traces of volcanic sulfur from two major eruptions newly dated to 536 CE and 540 CE in ice cores from Greenland and Antarctica.

An international team of climate scientists led by Dr. Matthew Toohey at the GEOMAR Helmholtz Centre for Ocean Research Kiel and Prof. Dr. Kirstin Krüger of the University of Oslo (UiO), with financial support from the Centre for Earth Evolution and Dynamics (CEED) at the UiO, have investigated the time period using the new ice core data, historical evidence and climate models. As they write in the international journal Climatic Change, the impact of the volcanic double event of 536/540 on Northern Hemisphere climate was stronger than any other documented or reconstructed event of the past 1200 years. "One of the eruptions would have led to a significant cooling of the Earth's surface. Two of them, so close in time, caused what is probably the coldest decade of the past 2000 years," says Dr. Matthew Toohey from GEOMAR, lead author of the study today at a press conference at the annual EGU Meeting in Vienna where he presented the results.

To simulate the impact of the 536 and 540 eruptions, the scientists used the available data from ice cores and the descriptions of the solar dimming from contemporary scholars. With this data they estimated the magnitude of the eruptions and their approximate locations on Earth, and then simulated the spread and impacts of the aerosol clouds resulting from the volcanic injection of sulfur into the stratosphere. This revealed that following the eruptions, the solar radiation at the Earth's surface was strongly reduced over the Northern Hemisphere for several years, and caused decreases in the hemispheric average temperature of up to 2 degrees Celsius.

link.

Carnian/Norian Boundary Environmental Changes Were NOT Caused by Methane Hydrates or Volcanic Eruptions

Paleoenvironmental changes across the Carnian/Norian boundary in the Black Bear Ridge section, British Columbia, Canada

Authors:

Onoue et al

Abstract:

The Black Bear Ridge section in northeastern British Columbia, Canada, consists of a continuously exposed sequence of Upper Carnian through Lower Norian (Upper Triassic) continental margin strata. The section has been proposed as a candidate Global Stratotype Section and Point (GSSP) for the Carnian/Norian boundary (CNB). In order to assess Late Carnian to Early Norian environmental changes recorded in the section, we examined stratigraphic variations in 87Sr/86Sr, δ13C, and δ18O values, and also values of redox sensitive elements (V, Ni and Cr), in the CNB interval. The study section is located along the north shore of Williston Lake, northeastern British Columbia. The Black Bear Ridge section was deposited in a distal ramp environment on the passive western margin of the North American craton.

The strata across the CNB display a positive shift in δ13C values and a corresponding increase in the redox indices V/(V + Ni) and V/Cr. The synchronous increase in δ13C values and redox indices suggests that burial rates of marine organic carbon increased in response to the development of anoxic conditions in the water column. An increase in δ13C values in carbonate rocks across the CNB has also been reported from Upper Triassic sections in the western Tethys (e.g., in the Pizzo Mondello section, Sicily), which suggests that the development of anoxic conditions within the CNB interval was widespread, affecting both the Panthalassan Ocean and Tethyan Sea. The geochemical data from this study, as well as from research into conodont biostratigraphy in the Black Bear Ridge section, show that the onset of oceanic anoxic conditions may have been responsible for the faunal turnover event at the CNB. The cause of this anoxic event is unknown, but the 87Sr/86Sr and δ13C isotope data largely exclude the possibility that the event was triggered by dissociation of methane hydrates and degassing related to large-scale volcanic activity.

Did Massive Northern Hemisphere Volcanic Eruptions Warm and Disrupt the Pleistocene Quaternary Antarctic Ice Sheet?

Massive volcanic eruptions could cause localised warming that might destabilise some of the world's biggest ice sheets, according to new research from Durham University.

Scientists investigated links between very large volcanic eruptions and polar temperatures during the last Ice Age.

Their findings suggest that some periods of Antarctic warming between 30,000 to 80,000 years ago were triggered by huge volcanic eruptions in the Northern Hemisphere that caused a shift in the world's weather patterns.

The Northern Hemisphere cooled as volcanic particles reflected the sun's heat, forcing warmer weather fronts south which led to warming in Antarctica, the researchers said.

Conversely, their research suggests that Southern Hemisphere eruptions could also have triggered abrupt warming in Greenland during the last Ice Age.

link.

Central Atlantic Magmatic Province was GeoChronologically Aligned WIth Triassic Jurassic Mass Extinction

Geochemical consequences of intense pulse-like degassing during the onset of the Central Atlantic Magmatic Province

Authors:

Paris et al

Abstract:

The Triassic–Jurassic boundary (TJB) is marked by one of the five largest mass extinctions of the Phanerozoic and the eruption of a large igneous province: the Central Atlantic Magmatic Province (CAMP). The TJB is characterized by a carbonate production crisis, by negative excursions in the carbon isotopic ratio of buried organic matter, and by successive peaks in atmospheric CO2. Here we use the numerical model GEOCLIM to explore the possible connections between the CAMP emplacement and the observed carbon cycle perturbations. Different degassing scenarios linked to the CAMP eruption are explored. We show that the emission of realistic amounts of CO2 that follow a geologically constrained degassing scenario as short-term peaks (less than 10 ka) leads to successive decrease in carbonate production, as observed in the geological record. We also calculate the evolution of carbon isotopes and show that our model reproduces the amplitude of the isotopic excursion with a volcanic degassing of CO2 characterized by a carbon isotopic composition of − 20‰. Such low values could be associated to carbon pools of light isotopic composition located at the transition zone [Cartigny, P. 2010, Earth and Planetary Science Letters, v. 296, p. 329–339] and not necessarily to biogenic methane release. Finally, the model predicts a succession of short-term CO2 rises, with an amplitude in close agreement with available proxy-based reconstructions.

Dr Gerta Keller Trumpets a Charge: Multiple Papers About Deccan Traps and the the K-Pg/KT Mass Extinction

Dr Keller has been leading an insurgency against the idea the Chicxulub impact was the underlying event that brought about the Cretaceous-Paleogene (K-Pg) Mass Extinction (formerly the KT Extinction).  This is rather contrarian to the generally accepted theory.  

The journal Paleaeogeography, Palaeoclimateology, Palaeoecology has an issue dedicated to how volcanic eruptions impacted (see what I did there?) past mass extinctions (or didn't as it may be).  That's the reason for all the volcano related posts this past week.  

Dr Keller's 'team' has a large number of articles in the publication.  Rather than do my traditional one-paper-per-post method, I am going to do a list here of each.  The reason being I don't buy her hypothesis that the Deccan Traps caused the mass extinction during the Maastrichtian.  I've posted as much since the evidence comparing mass extinctions already strongly tied to volcanic eruptions is rather different from what is present for the K-Pg Extinction.  I wrote as much in the Stop Dreaming post.  

That said, I am sure the Deccan Traps did cause some environmental impacts (see!), but they are insufficient to have caused the mass extinction.

While I admire tenacity, I think she has crossed over to religion.  However, rather than ignoring the recent papers, since they are peer reviewed papers in a respected journal, I am going to link to each here with a very short title and a description of each and a short comment.

Upheavals during the Late Maastrichtian: Volcanism, climate and faunal events preceding the end-Cretaceous mass extinction. Keller et al present their case the Maastrichtian Cretaceous was a time a climate upheaval and ecological degradation caused by the Deccan Traps with the ecology dominated by opportunistic, disaster taxa.  My comment: T rex.  Too big.

A multi-proxy approach to decode the end-Cretaceous mass extinction. Punekar argues there are multiple bits of evidence suggest the Deccan Traps caused the mass extinction at the K-Pg, especially the release of 12 to 28 teratons of carbon. Comment: Unfortunately, in the same journal edition, the OAE1 from the Early Aptian Cretaceous is stated to have been caused by the release of 20 teratons of carbon. The OAE1 was a mass extinction but a very, very mild one. Additionally, in a surprise result, calciferous plankton actually grow MORE with higher carbon dioxide levels, not less as was expected.

Tracing acidification induced by Deccan Phase 2 volcanism. Font et al ID some potential evidence of aquatic acidification at the end of the Deccan 2 Eruptions. These are located in India. Comment: Best to check to see how global this was before making a claim of global occurrence.

Palaeoenvironmental changes associated with Deccan volcanism, examples from terrestrial deposits from Central India. Fantasia et al present evidence of local impacts of the Deccan Traps caused stressed environment from India. Their claim is the DT caused environmental stress and could have made the Maastrichtian fauna vulnerable to a mass extinction at the end of the Cretaceous. Comment: Possible, but this could be completely local. Mount ST Helens did enormous damage locally, but only modestly globally.

Climatic fluctuations and sea-surface water circulation patterns at the end of the Cretaceous era: Calcareous nannofossil evidence. Thibault et al make the argument surface plankton became stressed and lost species during the proposed Deccan Warmings. However, 100k to 140k years before the K-Pg Boundary, the plankton had regained their species richness. Comment: Interesting. Given the problems of IDing what forminifers are what species I'd be cautious. The recovery would suggest whatever stress caused by the DTs had ended though.

Did the Siberian Traps Begin With an Ooze or a Bang?

The onset of flood volcanism in the north-western part of the Siberian Traps: Explosive volcanism versus effusive lava flows

Authors:

Jerram et al

Abstract:

The Siberian Traps large igneous province was formed during the end-Permian, about 252 Ma ago. Basaltic melt was injected into the organic and salt rich Tunguska sedimentary basin, forming interconnected sill complexes and associated hydrothermal vent complexes. Thick deposits of basaltic tuff and tephra covered the paleosurface before the onset of flood volcanism, commonly taken as direct evidence for the explosive nature of the initial phase of volcanism. The field work in this study revealed that tuffs are virtually absent along a 150 km long transect along the Dyupkun lake and Kureika river, even though tuff is shown on available geological maps. Towards the south and west, the transition between the end-Permian sediments and the flood basalts is either characterized by thin (2–5 m) to no tephra deposits (Khantaika area), hyaloclastites and associated lake-deposited tephra (Kureika area), or massive tephra deposits from local eruptive centers (Severnaya area). The new results can be put into the context of other studies about volcanic tuff horizons in Siberia, and questions the notion of province-scale explosive volcanism in Siberia during the onset of flood volcanism. Moreover, the main thicknesses of explosive tuff deposits, up to 700 m, are located in the central and southern parts of the province where the LIP erupted through thick Cambrian salt and carbonate sequences. Since numerous phreatomagmatic pipes are present in these areas, we suggest a causal relationship between deep magma–sediment interactions, explosive eruptions and the resulting environmental stress that initiated the end-Permian mass extinction.

Australian Kalkarindji Continental Flood Basalt Probably did NOT Cause Cambrian Mass Extinction

The Giant Lavas of Kalkarindji: rubbly pāhoehoe lava in an ancient continental flood basalt province

Authors:

Marshall et al

Abstract:

The Kalkarindji continental flood basalt province of northern Australia erupted in the mid Cambrian (c. 511-505 Ma). It now consists of scattered basaltic lava fields, the most extensive being the Antrim Plateau Volcanics (APV) – a semi-continuous outcrop (c. 50,000 km2) reaching a maximum thickness of 1.1 km. Cropping out predominately in the SW of the APV, close to the top of the basalt succession, lies the Blackfella Rockhole Member (BRM). Originally described as ‘basaltic agglomerate’ the BRM has, in recent years, been assumed to be explosive tephra of phreatomagmatic origin, thus providing a potent vehicle for volatile release to the upper atmosphere. Our detailed field investigations reveal that this basaltic agglomerate is, in reality, giant rubble collections (15–20 m thick) forming the upper crusts of rubbly pāhoehoe lava units 25–40 m thick; covering 18,000–72,000 km2 and an estimated volume of 1,500–19,200 km3. These flows, rheologically but not chemically, distinct from the majority of Kalkarindji lavas, indicate a fundamental change in eruption dynamics. A low volatile content, induced high amounts of pre-eruptive degassing causing super-cooling and an increase in crystal nucleation and viscosity. A more viscous lava and a consistently faster rate of effusion (analogous to that of Laki, Iceland) created the flow dynamics necessary to disturb the lava crust to the extent seen in the BRM. Volatile release is estimated at 1.65 × 104–2.11 × 105 Tg total CO2 at a rate of 867 Tg a- 1 and 9.07 × 103–1.16 × 105 Tg SO2 at 476.50 Tg a- 1. These masses accounted for 0.5% of Cambrian atmospheric conditions whilst limiting factors reduced the effect of volatile delivery to the atmosphere, thus any potential global impact caused by these flows alone was minimal.

Flood Basalts Don't Cause Mass Extinctions Through Sulphuric Acid

Selective environmental stress from sulphur emitted by continental flood basalt eruptions

Authors:

Schmidt et al

Abstract:

Several biotic crises during the past 300 million years have been linked to episodes of continental flood basalt volcanism, and in particular to the release of massive quantities of magmatic sulphur gas species. Flood basalt provinces were typically formed by numerous individual eruptions, each lasting years to decades. However, the environmental impact of these eruptions may have been limited by the occurrence of quiescent periods that lasted hundreds to thousands of years. Here we use a global aerosol model to quantify the sulphur-induced environmental effects of individual, decade-long flood basalt eruptions representative of the Columbia River Basalt Group, 16.5–14.5 million years ago, and the Deccan Traps, 65 million years ago. For a decade-long eruption of Deccan scale, we calculate a decadal-mean reduction in global surface temperature of 4.5 K, which would recover within 50 years after an eruption ceased unless climate feedbacks were very different in deep-time climates. Acid mists and fogs could have caused immediate damage to vegetation in some regions, but acid-sensitive land and marine ecosystems were well-buffered against volcanic sulphur deposition effects even during century-long eruptions. We conclude that magmatic sulphur from flood basalt eruptions would have caused a biotic crisis only if eruption frequencies and lava discharge rates had been high and sustained for several centuries at a time.

Evidence of Local Volcanic Eruptions From Orosirian PaleoProterozoic Tanzania

Age and geochemistry of coeval felsic volcanism and plutonism in the Palaeoproterozoic Ndembera Group of southwestern Tanzania: Constraints from SHRIMP U-Pb zircon and Sm-Nd data

Authors:

Bahame et al

Abstract:

The Ndembera metavolcanic rocks represent a continuum of compositions ranging from intermediate to more siliceous calc-alkaline trachyandesites-dacites-trachytes-rhyolites which have been intruded by largely metaluminous, calc-alkaline I-type granites in the Palaeoproterozoic Usagaran Belt of southewestern Tanzania. SHRIMP U-Pb zircon age data show that the Ndembera metavolcanic rocks were extruded at 1871 ± 30 Ma, an event that was largely coeval with the emplacement of cross-cutting microcline-biotite rich granites at 1896 ± 29 Ma.

Despite some compositional differences, both the granites and metavolcanic rocks share similar geochemical features including very coherent REE patterns characterized by enrichment of the LREE relative to the HREE (La/YbCN = 13.6-32.8 (average = 23.9) for metavolcanic rocks and La/YbCN = 10.8-38.2 (average = 21.8) for granites), negative Eu anomalies (Eu/Eu* = 0.45-1.01 (average = 0.83) for volcanic rocks and Eu/Eu* = 0.48-0.70 (average = 0.60) for granites), negative Ta, Ti and Nb anomalies (Nb/Lapm = 0.14-0.29 (average = 0.20 for volcanic rocks and Nb/Lapm = 0.01-0.37 (average = 0.16) for granites). The metavolcanic rocks have ɛNd(1871Ma) values of -0.03 to -4.89 and TDM ages of 2243 - 2714 which are broadly similar to those of the granites (ɛNd(1896 Ma) values of -3.56 to -4.59 and TDM ages of 2469 - 2646 Ma).

The geochemical similarities between the Ndembera volcanic rocks and granites, coupled with their similar emplacement age, suggest that the two rock suites were derived by the same processes in the same tectonic setting from an isotopically similar source. These geochemical features coupled with the paucity of mafic rocks suggest the derivation of the pluto-volcanic suite by crustal anatexis of basic meta-igneous rocks mixed with a minor metasedimentary component in an intra-continental setting. The more siliceous compositions in the suite may have formed by subsequent fractionation involving hornblende, plagioclase, biotite, titanite and apatite as indicated by the negative correlation between SiO2 and MgO, Fe2O3, Al2O3, CaO, TiO2 and P2O5, low Sr contents and negative Eu and Ti anomalies.

The ∼1.87 Ga coeval felsic volcanic and granitic magmatic event documented in the Ndembera Group is also a feature of the nearby Ubendian belt to the west pointing to a Palaeoproterozoic regional thermal event that occurred in southwestern and western Tanzania.

Evidence From Washington Direct Impacts of Volcanic Eruptions Insufficient to Cause Mass Extinctions

Extrinsic forcing of plant ecosystems in a large igneous province: The Columbia River flood basalt province, Washington State, USA

Authors:

Ebinghaus et al

Abstract:

Volcanism associated with large igneous provinces (LIPs) has been implicated in both global climate and environmental change. To determine the impact of LIP volcanism on plant ecology we have examined plant community succession in sedimentary interbeds of the Columbia River flood basalt province (CRBP; northwest United States). Interbasaltic vegetation is characterized by primary succession communities that inhabit fresh lava surfaces until terminated by the next eruptive event, and it is assumed that longer volcanic hiatuses should lead to more mature plant communities. This expected succession trajectory is contradicted by palynological data that show that seral succession declines during the phase of waning CRPB volcanism and prolonged interbed intervals. Frequent volcanic activity and increased deposition of Snake River Plain hotspot ashes during this phase resulted in ecological disturbance of intralava field vegetation. Together with geochemical proxies from interbed sediments, this suggests that CRBP flora was largely driven by extrinsic forcing, and implies that LIP volcanism of similar scale and magnitude to that of the CRBP had a limited environmental impact. This study supports the theory that past biotic extinctions were triggered by numerous factors rather than a single geological event.

Super Volcanoes may NOT be Triggered by Internal Pressure Buildup

Supervolcanoes, massive eruptions with potential global consequences, appear not to follow the conventional volcano mechanics of internal pressure building until the volcano blows. Instead, a new study finds, such massive magma chambers might erupt when the roof above them cracks or collapses.

Knowledge of triggering mechanisms is crucial for monitoring supervolcano systems, including ones that lie beneath Yellowstone National Park and Long Valley, California, according to the study led by Patricia Gregg, University of Illinois professor of geology, in collaboration with professor Eric Grosfils of Pomona College and professor Shan de Silva of Oregon State University. The study was published in the Journal of Volcanology and Geothermal Research. Gregg also presented the findings this week at the annual meeting of the Geological Society of America.

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Supervolcano Eruptions Have Very Short Fuses

Repeatedly throughout Earth's history, giant pools of magma greater than 100 cubic miles in volume have formed a few miles below the surface.

They are the sources of super-eruptions - gigantic volcanic outbursts that throw 100 times more superheated gas, ash and rock into the atmosphere than run-of-the-mill eruptions, enough to blanket continents and plunge the globe into decades-long volcanic winters.

The most recent super-eruption took place about 27,000 years ago in New Zealand, well before humans kept records of volcanic eruptions and their aftermath. Geologists today are studying deposits from past super-eruptions to try and understand where and how rapidly these magma bodies develop and what causes them to eventually erupt. Despite considerable study, geologists are still debating how quickly these magma pools can be activated and erupted, with estimates ranging from millions to hundreds of years.

Now a team of geologists have developed a new "geospeedometer" that they argue can help resolve this controversy by providing direct measurements of how long the most explosive types of magma existed as melt-rich bodies of crystal-poor magma before they erupted. They have applied their new technique to two super-eruption sites and a pair of very large eruptions and found that it took them no more than 500 years to move from formation to eruption.

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Evidence of Giant, Explosive Volcanic Eruptions During the Aptian Cretaceous

Aptian giant explosive volcanic eruptions in the Songliao Basin and northeast Asia: A possible cause for global climate change and OAE-1a

Authors:

Wang et al

Abstract:

Volcanism is a natural climate force that causes variations in temperatures. The Aptian Oceanic Anoxic Event 1a (OAE-1a) was preceded by a prominent negative C-isotope excursion attributed to major volcanism of the Ontong Java plateau (OJP), which presumably resulted in a pCO2 increase and a climatic change. However, the OJP alone may not adequately explain some important isotopic signatures such as the negative strontium-isotope excursion from 125 Ma to 113 Ma that is recorded in the corresponding marine deposits. We present an independent and hitherto undocumented case, the giant Aptian volcanism in the Songliao Basin and northeast Asia (SB-V) on the Cretaceous active continental margin between the Eurasian and the Pacific plates, which covered an area of ca. 2.3 × 106 km2, nearly matching the simultaneous case of the OJP. Intensive strong, explosive volcanic eruptions of the SB-V occurred at 121–109 Ma and introduced a large volume of fine-grained volcanic ash and degassing volatiles into the atmosphere. The Aptian isotopic ratios (87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) of marine carbonates from the Mid-Pacific shift in values between their Barremian pre-excursion high values and the negative magmatic values of the SB-V. The transient global cooling at the onset of the OAE-1a coincided with the beginning of the violent acidic eruption of the SB-V (119.9–120.2 Ma). We therefore infer that the SB-V must have played a role in the Aptian global climatic changes and OAE-1a through the heavy fall of volcanic dust and the outgassing of aerosol and greenhouse gases.

Understanding Supervolcanoes Like Yellowstone

Linking rapid magma reservoir assembly and eruption trigger mechanisms at evolved Yellowstone-type supervolcanoes

Authors:

Wotzlaw et al

Abstract:

The geological record contains evidence of volcanic eruptions that were as much as two orders of magnitude larger than the most voluminous eruption experienced by modern civilizations, the A.D. 1815 Tambora (Indonesia) eruption. Perhaps nowhere on Earth are deposits of such supereruptions more prominent than in the Snake River Plain–Yellowstone Plateau (SRP-YP) volcanic province (northwest United States). While magmatic activity at Yellowstone is still ongoing, the Heise volcanic field in eastern Idaho represents the youngest complete caldera cycle in the SRP-YP, and thus is particularly instructive for current and future volcanic activity at Yellowstone. The Heise caldera cycle culminated 4.5 Ma ago in the eruption of the ∼1800 km3 Kilgore Tuff. Accessory zircons in the Kilgore Tuff display significant intercrystalline and intracrystalline oxygen isotopic heterogeneity, and the vast majority are 18O depleted. This suggests that zircons crystallized from isotopically distinct magma batches that were generated by remelting of subcaldera silicic rocks previously altered by low-δ18O meteoric-hydrothermal fluids. Prior to eruption these magma batches were assembled and homogenized into a single voluminous reservoir. U-Pb geochronology of isotopically diverse zircons using chemical abrasion–isotope dilution–thermal ionization mass spectrometry yielded indistinguishable crystallization ages with a weighted mean 206Pb/238U date of 4.4876 ± 0.0023 Ma (MSWD = 1.5; n = 24). These zircon crystallization ages are also indistinguishable from the sanidine 40Ar/39Ar dates, and thus zircons crystallized close to eruption. This requires that shallow crustal melting, assembly of isolated batches into a supervolcanic magma reservoir, homogenization, and eruption occurred extremely rapidly, within the resolution of our geochronology (103–104 yr). The crystal-scale image of the reservoir configuration, with several isolated magma batches, is very similar to the reservoir configurations inferred from seismic data at active supervolcanoes. The connection of magma batches vertically distributed over several kilometers in the upper crust would cause a substantial increase of buoyancy overpressure, providing an eruption trigger mechanism that is the direct consequence of the reservoir assembly process.