SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption

The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963–1967. Two vertically cored boreholes, to 152 and 192 m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181 m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181 m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25–124 ∘C. A third cored borehole, inclined 55∘ in a 264∘ azimuthal direction to 354 m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100 m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25–141 ∘C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve

Fire in the hole: recreating volcanic eruptions with cannon blasts

Artificial volcanic plumes, fired from cannons loaded with ash plucked from the slopes of Iceland, may help researchers better monitor disruptive eruptions

Experimental interaction of magma and "dirty" coolants

International audienceThe presence of water at volcanic vents can have dramatic effects on fragmentation and eruption dynamics, but little is known about how the presence of particulate matter in external water will further alter eruptions. Volcanic edifices are inherently "dirty" places, where particulate matter of multiple origins and grainsizes typically abounds. We present the results of experiments designed to simulate non-explosive interactions between molten basalt and various "coolants," ranging from homogeneous suspensions of 0 to 30 mass% bentonite clay in pure water, to heterogeneous and/or stratified suspensions including bentonite, sand, synthetic glass beads and/or naturally-sorted pumice. Four types of data are used to characterise the interactions: (1) visual/video observations; (2) grainsize and morphology of resulting particles; (3) heat-transfer data from a network of eight thermocouples; and (4) acoustic data from three force sensors. In homogeneous coolants with ~20% sediment, heat transfer is by forced convection and conduction, and thermal granulation is less efficient, resulting in fewer blocky particles, larger grainsizes, and weaker acoustic signals. Many particles are droplet-shaped or/and "vesicular," containing bubbles filled with coolant. Both of these particle types indicate significant hydrodynamic magma-coolant mingling, and many of them are rewelded into compound particles. The addition of coarse material to heterogeneous suspensions further slows heat transfer thus reducing thermal granulation, and variable interlocking of large particles prevents efficient hydrodynamic mingling. This results primarily in rewelded melt piles and inefficient distribution of melt and heat throughout the coolant volume. Our results indicate that even modest concentrations of sediment in water will significantly limit heat transfer during non-explosive magma-water interactions. At high concentrations, the dramatic reduction in cooling efficiency and increase in mingling help to explain globular peperite, and provide information relevant to analyses of premixing associated with highly-explosive molten fuel-coolant interactions in debris-filled volcanic vents

Identifying magma-water interaction from the surface features of ash particles

The deposits from explosive volcanic eruptions (those eruptions that release mechanical energy over a short time span(1)) are characterized by an abundance of volcanic ash(2,3). This ash is produced by fragmentation of the magma driving the eruption and by fragmenting and ejecting parts of the pre-existing crust (host rocks). Interactions between rising magma and the hydrosphere (oceans, lakes, and ground water) play an important role in explosive volcanism(4,5), because of the unique thermodynamic properties of water that allow it to very effectively convert thermal into mechanical energy, Although the relative proportion of magma to host-rock fragments is well preserved in the pyroclastic rocks deposited by such eruptions, it has remained difficult to quantitatively assess the interaction of magma with liquid water from the analysis of pyroclastic deposits(2-5). Here we report the results of a study of natural pyroclastic sequences combined with scaled laboratory experiments. We find that surface features of ash grains can be used to identify the dynamic contact of magma with liquid water, The abundance of such ash grains can then be related to the water/magma mass ratios during their interaction

DOI:10.1068/htjr058 Thermophysical properties of a volcanic rock material

Abstract. To simulate and predict the behaviour of a lava flow, it is essential to have a thorough knowledge of its thermophysical properties. Therefore, thermal conductivity, specific heat, and viscosity of volcanic rock material were determined in a wide temperature range. Especially, the properties of the molten material were investigated in detail. The material was taken from the Pietre-Cotte lava flow located on the isle of Vulcano, north of Sicily. The thermal conductivity of the material was determined in the temperature range 293 ^ 1623 K by the hot-wire method. Melting occurs above 1100 K. The specific heat was measured by differential scanning calorimetry between 347 and 1671K. The viscosity of the lava melt was determined with a rotational viscometer HAAKE M5. The viscometer was enclosed in a high-temperature furnace optimised for the temperature range 1373 ^ 1598 K.

Fragmentation experiments with Havre melt: dry and induced fuel-coolant interaction runs

Here we present the data records (raw data) from 19 fragmentation experiments. In these runs silicic HVR254 dome rock (retrieved from the submarine Havre volcano) was crushed, remelted and fragmented using two different experimental settings: 1. dry runs (records labelled "D"): melt was fragmented by injection of pressurized Ar gas. 2. induced fuel-coolant interaction runs (records labelled "IFCI"): a water layer was established on top of the melt, before gas was injected from below. This caused fragmentation of the melt plug under IFCI conditions. Note that the runs D07, D08, D09, IFCI08 and IFCI09 used a reduced melt mass (100g instead of 250g). Files contain (separated by column) records of: time, trigger signal, force, pressure, microphone, electric field, seismic data. The units and amplification settings used are provided in the file headers. In addition, the results of morphometry analysis (t-tests) are provided in a pdf file. The morphometric analyses of natural ash focused exclusively on the curvi-planar grains dominant in Havre ash samples, labelled "Nat1" - "Nat6". Four types of experimental grains were compared with them: • “DG”: particles from dry runs, from the lab floor • “IG”: grains from open IFCI runs, from the lab floor • “IW”: very small particles from open IFCI runs deposited in water droplets on the walls and ceiling around the experimental area • “IU”: particles from IFCI runs with U-tube, from the water bow