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www.solid-earth-discuss.net/3/975/2011/
doi:10.5194/sed-3-975-2011
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Floating sandstones off El Hierro (Canary Islands, Spain): the peculiar case of the October 2011 eruption
1Dept. of Earth Sciences, CEMPEG, Uppsala University, Sweden
2Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
3Institute of Geosciences, University of Bremen, Germany
4Dept. of Earth and Planetary Sciences, McGill University, Canada
5Dept. of Physics (Geology), GEOVOL, University of Las Palmas, Gran Canaria, Spain
6Dept. of Earth and Environmental Sciences, Ludwig-Maximilians Universität (LMU), Munich, Germany
7Leibniz-Institute for Oceanography, IFM-GEOMAR, Kiel, Germany
8Geological Survey of Sweden, Uppsala, Sweden
9School of Geographical and Earth Sciences, University of Glasgow, UK
10SYRMEP Group, Sincrotrone Trieste S.C.p.A, Basovizza, Trieste, Italy
11Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, 56124 Pisa, Italy
Abstract. The eruption that started off the south coast of El Hierro, Canary Islands, in October 2011 has emitted intriguing eruption products found floating in the sea. These specimens appeared as floating volcanic "bombs" that have in the meantime been termed "restingolites" (after the close-by village of La Restinga) and exhibit cores of white and porous pumice-like material. Currently the nature and origin of these "floating stones" is vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have collected and analysed the structure and composition of samples and compared the results to previous work on similar rocks found in the archipelago. Based on their high silica content, the lack of igneous trace element signatures, and the presence of remnant quartz crystals, jasper fragments and carbonate relicts, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary rocks that were picked up and heated by the ascending magma causing them to partially melt and vesiculate. They hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies in the Canary Islands as well as in similar Atlantic islands that rest on sediment/covered ocean crust (e.g. Cape Verdes, Azores). The occurrence of these "restingolites" does therefore not indicate the presence of an explosive high-silica magma that is involved in the ongoing eruption.
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Citation: Troll, V. R., Klügel, A., Longpré, M.-A., Burchardt, S., Deegan, F. M., Carracedo, J. C., Wiesmaier, S., Kueppers, U., Dahren, B., Blythe, L. S., Hansteen, T., Freda, C., Budd, D. A., Jolis, E. M., Jonsson, E., Meade, F., Berg, S., Mancini, L., and Polacci, M.: Floating sandstones off El Hierro (Canary Islands, Spain): the peculiar case of the October 2011 eruption, Solid Earth Discuss., 3, 975-999, doi:10.5194/sed-3-975-2011, 2011. Bibtex EndNote Reference Manager XML
