Dr. Ben Ellis

Dr.  Ben Ellis

Dr. Ben Ellis

Lecturer at the Department of Earth Sciences

ETH Zürich

Inst. für Geochemie und Petrologie

NW E 76.2

Clausiusstrasse 25

8092 Zürich

Switzerland

Additional information

Research area

I am a volcanologist interested in combining physical volcanology, geochemistry and geochronology to better understand how volcanoes work.  My research interests span, but are not limited to, the following fields:

 

Physical Volcanology: During explosive eruptions the processes occurring from vent to deposit are extremely complex and vary hugely in four dimensions.  You may wonder how we can ever deduce anything about the processes ongoing in explosive eruptions and pyroclastic density currents, but with detailed field observations coupled to precise sampling and geochemical analyses it is possible to understand (at least in part) the behaviour of the parent current.  My current interests involve coupling the classic field-based lithofacies analyses of pyroclastic rocks with novel geochemical and isotopic techniques.

 

Super-eruptions: Super-eruptions are one of the largest geological hazards to mankind, with the largest eruptions being devastating on scales from regional to global.  The interesting nature of these deposits proves a magnet to modellers of many descriptions.  Unfortunately, in many cases the input (field-based) data for such models has not been revisited since the 1950-60s.  I am interested in constraining the simplest, first order facts about these events, such as how much material erupts, how often it erupts and what happens to it once it has erupted.  To do this requires the ability to ‘fingerprint’ magma batches, commonly via a variety of geochemical means (trace elements in glasses, mineral compositions, isotopic compositions).  Constraining the temporal aspects of ‘super-eruptions’ requires high-precision geochronology via ID-TIMS, SIMS or Ar/Ar as appropriate.  This data is generated via collaborations with some top labs (SUERC, Boise State, ETH).

 

Groundmass crystallisation: Most petrological studies are interested in reconstructing the conditions in the magmatic plumbing systems.  To be able to do this requires the ability to ‘see through’ any post-eruption modification of compositions.  This is where understanding groundmass crystallisation of volcanic products comes in.  In basaltic systems, cooling rate is a first order control on the bulk crystallinity of the deposit (think pillow lavas).  In large rhyolitic ignimbrites and lavas, a small proportion of the material is glassy, but the vast majority is crystallised.  The crystallisation of a rhyolitic liquid under surficial conditions has implications for the compositions of both the bulk and phenocrysts within a deposit.  We are using a variety of micro-analytical and bulk techniques to address the question of how crystalline a given sample is, and how these changes reflect variations in cooling history.

 

Magmatic systems: I am interested in how magmas (particularly silicic magmas) are generated, stored and erupted and how these conditions may change in the lead up to a big eruption.  In recent times this has involved investigating the Sr isotopic homogeneity of rhyolitic systems, the nature of cumulates in volcanic deposits and the major and trace elemental compositions of melt inclusions.  To understand the petrological evolution of volcanic systems, high quality micro-analytical data is required to constrain conditions such as temperature and pressure.  Fortunately at ETH a world-class array of analytical facilities exist to support such investigations.

 

 

Publications

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