Université de Fribourg

The Malpaisillo Formation: A sequence of explosive eruptions in the mid to late Pleistocene (Nicaragua, Central America)

Stoppa, Line ; Kutterolf, Steffen ; Rausch, Juanita ; Grobety, Bernard ; Pettke, Thomas ; Wang, Kuo-Lung ; Hemming, Sidney

In: Journal of Volcanology and Geothermal Research, 2018, vol. 359, p. 47–67

The subduction-related volcanic front in Nicaragua consists of the Tertiary “Coyol” member in the eastern highlands and the Quaternary to recent volcanic arc within the Nicaraguan depression. Although the Holocene to recent explosive volcanism has been studied extensively no detailed work has been done on the products of explosive volcanism from Quaternary volcanic complexes comprising...

Université de Fribourg

A model based two-stage classifier for airborne particles analyzed with Computer Controlled Scanning Electron Microscopy

Meier, Mario Federico ; Mildenberger, Thoralf ; Locher, René ; Rausch, Juanita ; Zünd, Thomas ; Neururer, Christoph ; Ruckstuhl, Andreas ; Grobéty, Bernard

In: Journal of Aerosol Science, 2018, vol. 123, p. 1–16

Computer controlled scanning electron microscopy (CCSEM) is a widely-used method for single airborne particle analysis. It produces extensive chemical and morphological data sets, whose processing and interpretation can be very time consuming. We propose an automated two-stage particle classification procedure based on elemental compositions of individual particles. A rule-based classifier is...

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

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

Nejapa Tephra: The youngest (c. 1 ka BP) highly explosive hydroclastic eruption in western Managua (Nicaragua)

Rausch, Juanita ; Schmincke, Hans-Ulrich

In: Journal of Volcanology and Geothermal Research, 2010, vol. 192, no. 3-4, p. 159-177

Nejapa Maar (2.5 × 1.4 km, c. 120 m deep), the largest maar along the 15-km-long Holocene Nejapa–Miraflores Lineament (NML), is the source vent of the youngest relatively widespread basaltic tholeiitic tephra blanket (Nejapa Tephra: NT) in western central Nicaragua, as shown by isopachs and isopleths (Rausch and Schmincke, 2008). The NT covers an area of > 10 km² in W/NW Managua. The...