Degassing history of water, sulfur, and carbon in submarine lavas from Kilauea volcano, Hawaii

Major, minor, and dissolved volatile element concentrations were measured in tholeiitic glasses from the submarine portion (Puna Ridge) of the east rift zone of Kilauea Volcano, Hawaii. Dissolved H_(2)O and S concentrations display a wide range relative to nonvolatile incompatible elements at all depths. This range cannot be readily explained by fractional crystallization, degassing of H20 and S during eruption on the seafloor, or source region heterogeneities. Dissolved C0_2 concentrations, in contrast, show a positive correlation with eruption depth and typically agree within error with the solubility at that depth. We propose that most magmas along the Puna Ridge result from (I) mixing of a relatively volatile-rich, undegassed component with magmas that experienced low pressure (perhaps subaerial) degassing during which substantial H_(2)O, S, and C0_2 were lost, followed by (2) fractional crystallization of olivine, clinopyroxene, and plagioclase from this mixture to generate a residual liquid; and (3) further degassing, principally of C0_2 for samples erupted deeper than 1000 m, during eruption on the seafloor. The degassed end member may form at upper levels of the summit magma chamber (assuming less than lithostatic pressure gradients), during residence at shallow levels in the crust, or during sustained summit eruptions. The final phase of degassing during eruption on the seafloor occurs slowly enough to achieve melt/vapor equilibrium during exsolution of the typically CO_(2)-rich vapor phase. We predict that average Kilauean primary magmas with 16% MgO contain ~0.47 wt% H_(2)O, ~900 ppm S, and have δD values of ~-30 to -40‰. Our model predicts that submarine lavas from wholly submarine volcanoes (i.e., Loihi), for which there is no opportunity to generate the degassed end member by low pressure degassing, will be enriched in volatiles relative to those from volcanoes whose summits have breached the sea surface (i.e., Kilauea and Mauna Loa)

Deciphering histone 2A deubiquitination

The discovery of three different enzymes that deubiquitinate histone 2A

Identification and analysis of large paleo-landslides at Mount Burnaby, British Columbia

This is the author accepted manuscript. The final version is available from Geological Society of America via the DOI in this recordThis paper presents a multi-scale and multidisciplinary study of large, late Pleistocene or early Holocene slumps in Eocene sedimentary rocks at Mount Burnaby, just east of Vancouver, British Columbia (BC). Airborne LiDAR and field data were integrated into a GIS to understand the origin, kinematics, and subsequent history of the landslides. Products derived from the bare-earth LiDAR data include an engineering geomorphology map, shaded relief maps, and several LiDAR slope profiles. To understand the landslides better, we analyzed discontinuities and structural lineaments. The structure of the Eocene rocks underlying Mount Burnaby was compared with trends of local lineaments, and the shape of the coastline of Burrard Inlet and Indian Arm, and trends of regional faults and lineaments identified by previous researchers working in southwest BC. Two main joint systems likely played a key role in conditioning the north slope of Mount Burnaby for failure. The landslides probably happened during or soon after deglaciation of the area at the end of the Pleistocene on the steep north face of Mount Burnaby after a 200-m fall in relative sea level caused by glacio-isostatic uplift of the crust.We are grateful to BGC Engineering for its support of our research, and in particular acknowledge Alex Baumgard, who helped us secure LiDAR imagery and funding that allowed us to undertake the project. The research was supported with grants provided by Kinder Morgan Canada and the Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Grants to ds and jjc)

Is the standard Higgs scalar elementary?

In the standard electroweak model, the measured top quark mass requires a sizeable Yukawa coupling to the fundamental scalar. This large coupling alone might induce a dynamical breaking of the electroweak symmetry as well as non-perturbative effects. If such is the case, even a standard Higgs scalar as light as 80 GeV should have a non-negligible $t \bar{t}$ component induced by the top condensate.Comment: 8 pages, Latex fil

The Cordilleran Ice Sheet and the Glacial Geomorphology of Southern and Central British Colombia

This paper reviews the current state of knowledge about the Cordilleran Ice Sheet in southern and central British Columbia. Reconstructions of the ice sheet and the styles of ice expansion and déglaciation are based on extensive and varied glacigenic sediments and landforms that date from Late Wisconsinan (Fraser) Glaciation. Late-glacial lakes and sea level changes are also described and related to isostatic and eustatic effects. The timing of ice expansion and recession during Fraser Glaciation was markedly asymmetric: ice build-up commenced about 29 000 years BP, culminated between 14 500 and 14 000 years BP1 and déglaciation was largely completed by 11 500 years BP. Most of this interval appears to have been dominated by montane glaciation, which produced striking erosional landforms. A Cordilleran Ice Sheet existed from only about 19 000 to 13 500 years BP. An older glaciation, probably of Early Wisconsinan age, has been recognized from widespread exposures of drift that underlies Middle Wisconsinan non-glacial sediments. Pre-Wisconsinan drift is present near Vancouver. Drifts of late Tertiary to Middle Pleistocene age have been dated by association with volcanic sequences in the southern Coast Mountains and the central Interior, and by paleomagnetic studies in the southern Interior.On résume ici l'état des connaissances sur l'Inlandsis de la Cordillère du sud et du centre de la Colombie-Britannique. Les reconstitutions de l'inlandsis et les modes d'englaciation et de déglaciation sont fondés sur les formes et les sédiments glaciaires qui datent de la glaciation du Wisconsinien supérieur (Fraser). On décrit également les lacs tardiglaciaires et les changements du niveau marin en relation avec les conséquences sur les niveaux isostatique et eustatique. Les rythmes de la progression et du retrait glaciaire ont été tout à fait différents; la giaciation a commencé vers 29 000 BP, a connu son optimum entre 14 500 et 14 000 BP et la déglaciation était à toutes fins utiles terminée dès 11 500 BP. La plus grande partie de cette époque a été dominée par une glaciation de type alpin, qui a engendré des formes d'érosion remarquables. L'Inlandsis de la Cordillère n'a existé que de 19 000 à 13 500 BP. On a identifié une glaciation plus ancienne, probablement du Wisconsinien inférieur, à partir des affleurements répandus de dépôts glaciaires sous-jacents aux sédiments non glaciaires du Wisconsinien moyen. On a observé des dépôts glaciaires pré-wisconsiniens près de Vancouver. Les dépôts glaciaires datant du Tertiaire supérieur au Pleistocene moyen ont été datés par association aux séquences volcaniques du sud des montagnes Côtières et du centre de l'Intérieur et grâce à des études de paléomagnétisme menées dans le sud du système de l'Intérieur.Dieser Artikel gibt einen uberblick ûber den gegenwartigen Forschungsstand zur Kordilleren-Eisdecke im Sùden und im Zentrum von British Columbia. Die Rekonstruktionen der Eisdecke und der Art und Weise der Eisausdehnung und Enteisung stùtzen sich auf extensive und mannigfache glazigene Sedimente und Landformen, die aus der Spât-Wisconsin- (Fraser) Vereisung stammen. Spàtglaziale Seen und Meeresniveauwechsel werden auch beschrieben und in Beziehung zu isostatischen und eustatischen Auswirkungen gesetzt. Der zeitliche Ablauf der Eisausdehnung und des Eisrùckzugs wàhrend der Fraser-Vereisung war deutlich asymmetrisch : die Vereisung begann um etwa 29 000 Jahre v.u.Z., erreichte ihren Hôchststand zwischen 14 500 und 14 000 Jahren v.u.Z. und die Enteisung war weitgehend vollendet um 11 500 Jahre v.u.Z. Der grôfîte Tail dieses Zeitraums scheint von einer alpinen Vereisung beherrscht gewesen zu sein, welche eindrucksvolle Erosions-Landformen hervorbrachte. Eine Kordilleren-Eisdecke existierte nur von etwa 19 000 bis 13 500 Jahre v.u.Z. Eine altère Vereisung, môglicherweise aus dem frùhen Wisconsin konnte anhand ausgedehnter Anlagen von glazialen Ablagerungen, die sich unter nichtglazialen Sedimenten des mittleren Wiskonsin befinden, identifiziert werden. Abgelagerte Bildungen aus dem Spàttertiâr bis zum mittleren Pleistozân wurden in Verbindung mit vulkanischen Sequenzen in den Bergen der Sùdkùste und dem zentralen Landesinnern und mittels palàomagnetischen Studien im sûdlichen Landesinnern datiert

Mid-ocean-ridge rhyolite (MORR) eruptions on the East Pacific Rise lack the fizz to pop

Eruptions on the Alarcon Rise segment of the northern East Pacific Rise (23.55°N, 108.42°W) at 2500−2200 m below sea level (mbsl) produced the most compositionally diverse volcanic suite found along the submarine mid-ocean-ridge (MOR) system, offering an opportunity to compare mafic through silicic eruption styles at the same abyssal depth. Eruption styles that formed evolved volcanic rocks on the submarine MOR have not been studied in detail. The prevalence of lava flows along the MOR indicates that most eruptions are nonexplosive, but some volcaniclastic characteristics suggest that explosive styles also occur. Higher viscosities in intermediate (103–5 Pa·s) versus mafic (101 Pa·s) lavas on Alarcon Rise correspond with larger, more brecciated pillows, while highly viscous rhyolite lavas (106–7 Pa·s) formed rugged domes mostly composed of autoclastic breccia. Although high H2O contents (1.5–2.1 wt%), abundant volcaniclasts, and vesicularities up to 53% in rhyolite might imply eruption explosivity, limited fine-grained ash production and dispersal indicate an effusive origin. Higher viscosities of MOR rhyolite (MORR) magma and small eruption volumes, compared to MOR basalt (MORB), limit bubble coalescence and rapid magma ascent, two likely prerequisites for deep-marine eruption explosivity. This idea is supported by widespread dispersal of basaltic ash, but very limited production and dispersal of silicic ash on Alarcon Rise

The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches

We describe the impact of three simultaneous earthquake-triggered rock avalanches on the dynamics of Black Rapids Glacier, Alaska, by using spaceborne radar imagery and numerical modeling. We determined the velocities of the glacier before and after landslide deposition in 2002 by using a combination of ERS-1/ERS-2 tandem, RADARSAT-1, and ALOS PALSAR synthetic aperture radar data. Ice velocity above the debris-covered area of the glacier increased up to 14% after the earthquake but then decreased 20% by 2005. Within the area of the debris sheets, mean glacier surface velocity increased 44% within 2 years of the landslides. At the downglacier end of the lowest landslide, where strong differential ablation produced a steep ice cliff, velocities increased by 109% over the same period. By 2007, ice velocity throughout the debris area had become more uniform, consistent with a constant ice flux resulting from drastically reduced ablation at the base of the debris. Without further analysis, we cannot prove that these changes resulted from the landslides, because Black Rapids Glacier displays large seasonal and interannual variations in velocity. However, a full Stokes numerical ice flow model of a simplified glacier geometry produced a reversal of the velocity gradient from compressional to extensional flow after 5 years, which supports our interpretation that the recent changes in the velocity field of the glacier are related to landslide-induced mass balance changes

A robust sar speckle tracking workflow for measuring and interpreting the 3d surface displacement of landslides

We present a workflow for investigating large, slow‐moving landslides which combines the synthetic aperture radar (SAR) technique, GIS post‐processing, and airborne laser scanning (ALS), and apply it to Fels landslide in Alaska, US. First, we exploit a speckle tracking (ST) approach to derive the easting, northing, and vertical components of the displacement vectors across the rock slope for two five‐year windows, 2010–2015 and 2015–2020. Then, we perform post‐processing in a GIS environment to derive displacement magnitude, trend, and plunge maps of the landslide area. Finally, we compare the ST‐derived displacement data with structural lineament maps and profiles extracted from the ALS dataset. Relying on remotely sensed data, we estimate that the thickness of the slide mass is more than 100 m and displacements occur through a combination of slumping at the toe and planar sliding in the central and upper slope. Our approach provides information and interpretations that can assist in optimizing and planning fieldwork activities and site investigations at landslides in remote locations

Oceanic Zircon Records Extreme Fractional Crystallization of MORB to Rhyolite on the Alarcon Rise Mid-Ocean Ridge

The first known occurrence of rhyolite along the submarine segments of the mid-ocean ridge (MOR) system was discovered on Alarcon Rise, the northernmost segment of the East Pacific Rise (EPR), by the Monterey Bay Aquarium Research Institute in 2012. Zircon trace element and Hf and O isotope patterns indicate that the rhyolite formed by extreme crystal fractionation of primary mid-ocean ridge basalt (MORB) sourced from normal to enriched MOR mantle with little to no addition of continental lithosphere or hydrated oceanic crust. A large range in zircon ϵHf spanning 11 ϵ units is comparable to the range of whole rock ϵHf from the entire EPR. This variability is comparable to continental granitoids that develop over long periods of time from multiple sources. Zircon geochronology from Alarcon Rise suggests that at least 20 kyr was needed for rhyolite petrogenesis. Grain-scale textural discontinuities and trace element trends from zircon cores and rims are consistent with crystal fractionation from a MORB magma with possible perturbations associated with mixing or replenishment events. Comparison of whole rock and zircon oxygen isotopes with modeled fractionation and zircon-melt patterns suggests that, after they formed, rhyolite magmas entrained hydrated mafic crust from conduit walls during ascent and/or were hydrated by seawater in the vent during eruption. These data do not support a model where rhyolites formed directly from partial melts of hydrated oceanic crust or do they require assimilation of such crust during fractional crystallization, both models being commonly invoked for the formation of oceanic plagiogranites and dacites. A spatial association of highly evolved lavas (rhyolites) with an increased number of fault scarps on the northern Alarcon Rise might suggest that low magma flux for ∼20 kyr facilitated extended magma residence necessary to generate rhyolite from MORB