Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

The authors acknowledge Airbus Defence and Space for providing satellite imagery, financial support from Keele University and fieldwork grants from the Mineralogical Society of Great Britain and Ireland and the Volcanic and Magmatic Studies Group. LAB wishes to thank Leanne Patrick and James Watling for fieldwork assistance. The authors are grateful for the thorough and constructive comments from Guido Giordano and an anonymous reviewer, as well as the careful editorial handling of Kathy Cashman and Andrew Harris, which greatly improved this manuscript. Open access via Springer CompactPeer reviewedPublisher PD

Vegetation dieback as a proxy for temperature within a wet pyroclastic density current: A novel experiment and observations from the 6th of August 2012 Tongariro eruption

The 6th of August 2012 eruption of Te Maari (Mt Tongariro, New Zealand) generated wet pyroclastic density currents (PDCs) which caused widespread dieback of vegetation (singed, brown foliage) in their path. An absence of significant charcoal formation suggests that PDC temperatures were mostly below 250 °C. Textural evidence for liquid water being present in the matrices during emplacement (vesicles) suggests that temperatures were b100 °C. We determined a probable minimum PDC temperature using an experiment replicating the critical temperatures required to induce foliar browning in seven species affected by the eruption. In locations where all species exhibited browned foliage (or were defoliated), temperatures were probably ≥64 °C assuming a PDC duration of 60 s. In the more distal areas, where only the most susceptible species were browned while others remained healthy and unaffected, temperatures were probably around 51–58 °C. These results have relevance to volcanic hazard mitigation and risk assessment, especially on the popular Tongariro Alpine Crossing

Spherulite formation in obsidian lavas in the Aeolian Islands, Italy

The authors wish to gratefully acknowledge Andy Tindle (The Open University) for assistance with EMP analyses, and Richard Darton and David Evans (Keele University) for assistance with XRD and Prof Alun Vaughan and Nicola Freebody (University of Southampton) with Raman analyses. LAB is grateful to Sophie Blanchard for support with MATLAB. The authors acknowledge support from Keele University, and grants from the Mineralogical Society (UK and Ireland) and Volcanic and Magmatic Studies Group. The authors thank Silvio Mollo and Francesca Forni for their detailed and helpful comments.Peer reviewedPublisher PD

Terrestrial analogs and thermal models for Martian flood lavas

The recent flood lavas on Mars appear to have a characteristic “platy-ridged” surface morphology different from that inferred for most terrestrial continental flood basalt flows. The closest analog we have found is a portion of the 1783–1784 Laki lava flow in Iceland that has a surface that was broken up and transported on top of moving lava during major surges in the eruption rate. We suggest that a similar process formed the Martian flood lava surfaces and attempt to place constraints on the eruption parameters using thermal modeling. Our conclusions from this modeling are (1) in order to produce flows >1000 km long with flow thicknesses of a few tens of meters, the thermophysical properties of the lava should be similar to fluid basalt, and (2) the average eruption rates were probably of the order of 104 m3/s, with the flood-like surges having flow rates of the order of 105–106 m3/s. We also suggest that these high eruption rates should have formed huge volumes of pyroclastic deposits which may be preserved in the Medusae Fossae Formation, the radar “stealth” region, or even the polar layered terrains

High-density support matrices: Key to the deep borehole disposal of spent nuclear fuel

Deep (4–5 km) boreholes are emerging as a safe, secure, environmentally sound and potentially cost-effective option for disposal of high-level radioactive wastes, including plutonium. One reason this option has not been widely accepted for spent fuel is because stacking the containers in a borehole could create load stresses threatening their integrity with potential for releasing highly mobile radionuclides like 129I before the borehole is filled and sealed. This problem can be overcome by using novel high-density support matrices deployed as fine metal shot along with the containers. Temperature distributions in and around the disposal are modelled to show how decay heat from the fuel can melt the shot within weeks of disposal to give a dense liquid in which the containers are almost weightless. Finally, within a few decades, this liquid will cool and solidify, entombing the waste containers in a base metal sarcophagus sealed into the host rock

Tectonic history of the South Tannuol Fault Zone (Tuva region of the northern Central Asian Orogenic Belt, Russia) : constraints from multi-method geochronology

In this study, we present zircon U/Pb, plagioclase and K-feldspar Ar-40/Ar-39 and apatite fission track (AFT) data along the South Tannuol Fault Zone (STFZ). Integrating geochronology and multi-method thermochronology places constraints on the formation and subsequent reactivation of the STFZ. Cambrian (similar to 510 Ma) zircon U/Pb ages obtained for felsic volcanic rocks date the final stage of STFZ basement formation. Ordovician (similar to 460-450 Ma) zircon U/Pb ages were obtained for felsic rocks along the structure, dating their emplacement and marking post-formational local magmatic activity along the STFZ. Ar-40/Ar-39 stepwise heating plateau-ages (similar to 410-400 Ma, similar to 365 and similar to 340 Ma) reveal Early Devonian and Late Devonian-Mississippian intrusion and/or post-magmatic cooling episodes of mafic rocks in the basement. Permian (similar to 290 Ma) zircon U/Pb age of mafic rocks documents for the first time Permian magmatism in the study area creating prerequisites for revising the spread of Permian large igneous provinces of Central Asia. The AFT dating and Thermal history modeling based on the AFT data reveals two intracontinental tectonic reactivation episodes of the STFZ: (1) a period of Cretaceous-Eocene (similar to 100-40 Ma) reactivation and (2) the late Neogene (from similar to 10 Ma onwards) impulse after a period of tectonic stability during the Eocene-Miocene (similar to 40-10 Ma)

Fluid Outflows From Venus Impact Craters: Analysis From Magellan Data

Many impact craters on Venus have unusual outflow features originating in or under the continuous ejecta blankets and continuing downhill into the surrounding terrain. These features clearly resulted from flow of low-viscosity fluids, but the identity of those fluids is not clear. In particular, it should not be assumed a priori that the fluid is an impact melt. A number of candidate processes by which impact events might generate the observed features are considered, and predictions are made concerning the rheological character of flows produced by each mechanism. A sample of outflows was analyzed using Magellan images and a model of unconstrained Bingham plastic flow on inclined planes, leading to estimates of viscosity and yield strength for the flow materials. It is argued that at least two different mechanisms have produced outflows on Venus: an erosive, channel-forming process and a depositional process. The erosive fluid is probably an impact melt, but the depositional fluid may consist of fluidized solid debris, vaporized material, and/or melt

Detrital zircon and apatite (U‐Th)/He geochronology of intercalated baked sediments: a new approach to dating young basalt flows

Simple numerical models suggest that many basaltic lava flows should sufficiently heat the sediments beneath them to reset (U‐Th)/He systematics in detrital zircon and apatite. This result suggests a useful way to date such flows when more conventional geochronological approaches are either impractical or yield specious results. We present here a test of this method on sediments interstratified with basalt flows of the Taos Plateau Volcanic Field of New Mexico. Nineteen zircons and apatites from two samples of baked sand collected from the uppermost 2 cm of a fluvial channel beneath a flow of the Upper Member of the Servilleta Basalt yielded an apparent age of 3.487 ± 0.047 Ma (2 SE confidence level), within the range of all published 40Ar/39Ar dates for other flows in the Upper Member (2.81–3.72 Ma) and statistically indistinguishable from the 40Ar/39Ar dates for basal flows of the Upper Member with which the studied flow is broadly correlative (3.61 ± 0.13 Ma). Given the high yield of 4He from U and Th decay, this technique may be especially useful for dating Pleistocene basalt flows. Detailed studies of the variation of (U‐Th)/He detrital mineral dates in sedimentary substrates, combined with thermal modeling, may be a valuable tool for physical volcanologists who wish to explore the temporal and spatial evolution of individual flows and lava fields.</p