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Université de Fribourg

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

Vonlanthen, Pierre ; Rausch, Juanita ; Ketcham, Richard A. ; Putlitz, Benita ; Baumgartner, Lukas P. ; Grobéty, Bernard

In: Journal of Volcanology and Geothermal Research, 2015, vol. 293, p. 1–12

The morphology of small volcanic ash particles is fundamental to our understanding of magma fragmentation, and in transport modeling of volcanic plumes and clouds. Until recently, the analysis of 3D features in small objects (< 250 μm) was either restricted to extrapolations from 2D approaches, partial stereo-imaging, or CT methods having limited spatial resolution and/or accessibility. In...

Université de Fribourg

Eifel maars: Quantitative shape characterization of juvenile ash particles (Eifel Volcanic Field, Germany)

Rausch, Juanita ; Grobéty, Bernard ; Vonlanthen, Pierre

In: Journal of Volcanology and Geothermal Research, 2015, vol. 291, p. 86–100

The Eifel region in western central Germany is the type locality for maar volcanism, which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water (i.e. phreatomagmatic eruptions). Sedimentary structures, deposit features and particle morphology found in many maar deposits of the West Eifel Volcanic Field (WEVF), in contrast...

Université de Fribourg

Local influences of geothermal anomalies on permafrost distribution in an active volcanic island (Deception Island, Antarctica)

Goyanes, G. ; Vieira, G. ; Caselli, A. ; Cardoso, M. ; Marmy, Antoine ; Santos, F. ; Bernardo, I. ; Hauck, Christian

In: Geomorphology, 2014, vol. 225, p. 57–68

This study aims at understanding the spatial distribution and characteristics of the frozen and unfrozen terrain in an alluvial fan on Deception Island, which is an active strato-volcano located in the Bransfield Strait (South Shetland Islands) with recent eruptions in 1967, 1969 and 1970. The alluvial fan is dominated by debris-flow, run-off and rock fall processes and permafrost occurs in...

Université de Fribourg

Pushing the volcanic explosivity index to its limit and beyond: constraints from exceptionally weak explosive eruptions at Kīlauea in 2008

Houghton, B.F. ; Swanson, D.A. ; Rausch, Juanita ; Carey, R.J. ; Fagents, S.A. ; Orr, T.R.

In: Geology, 2013, p. -

Estimating the mass, volume, and dispersal of the deposits of very small and/or extremely weak explosive eruptions is difficult, unless they can be sampled on eruption. During explosive eruptions of Halema'uma'u Crater (Kīlauea, Hawaii) in 2008, we constrained for the first time deposits of bulk volumes as small as 9–300 m³ (1 × 10⁴ to 8 × 10⁵ kg) and can demonstrate that they show...

Université de Fribourg

Airborne in-situ investigations of the Eyjafjallajökull volcanic ash plume on Iceland and over north-western Germany with light aircrafts and optical particle counters

Weber, Klaus ; Eliasson, J. ; Vogel, A. ; Fischer, C. ; Pohl, T. ; Haren, G. van ; Meier, M. ; Grobéty, Bernard ; Dahmann, D.

In: Atmospheric Environment, 2011, vol. 48, p. 9-21

During the time period of the eruption of the Icelandic volcano Eyjafjallajökull in April/May 2010 the Duesseldorf University of Applied Sciences has performed 14 research flights in situations with and without the volcanic ash plume over Germany. In parallel to the research flights in Germany three measurement flights have been performed by the University of Iceland in May 2010 over the western...

Université de Fribourg

Melilite-group minerals at Oldoinyo Lengai, Tanzania

Wiedenmann, Daniel ; Keller, Jörg ; Zaitsev, Anatoly N.

In: Lithos, 2010, p. -

Oldoinyo Lengai and the volcanic centres of the Lake Natron–Engaruka province contain melilite as a widespread mineral. Extraordinarily Na–Al-rich melilites (up to 6 wt.% Na₂O and 9 wt.% Al₂O₃) from recent explosive eruptions are among the most Na-rich ever reported. Their unusual mineral composition leads to optical properties with vivid birefringence colours of 2nd order. The...

Université de Fribourg

Tree-ring reconstruction of past lahar activity at Popocatépetl volcano, Mexico

Bollschweiler, Michelle ; Stoffel, Markus ; Vázquez Selem, Lorenzo ; Palacios, David

In: The Holocene, 2010, vol. 20, no. 2, p. 265-274

Lahars represent a major threat on the slopes of volcanoes all over the world. In order to realistically assess hazards, knowledge on the occurrence and timing of past lahar activity is of crucial importance. However, archival data on past events is usually scarce or completely missing. Tree-ring records have repeatedly proved to be a reliable data source for the reconstruction of past...

Bibliothèque cantonale jurassienne

Biodiversity during the Deccan volcanic eruptive episode

Khosla, Ashok ; Sahni, Ashok

In: Journal of Asian Earth sciences, 2003, vol. 21, p. 895

Bibliothèque cantonale jurassienne

Did impacts, volcanic eruptions, or climate change affect mammalian evolution?

Prothero, Donald R.

In: Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences, 2004, vol. 214, p. 283