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The role of small-scale convective instabilities at oceanic intra-plate volcanism

English title The role of small-scale convective instabilities at oceanic intra-plate volcanism
Applicant Tackley Paul
Number 119922
Funding scheme Project funding
Research institution Institut für Geophysik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geophysics
Start/End 01.07.2008 - 30.06.2009
Approved amount 55'584.00
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Keywords (7)

convection; lithophere-mantle interaction; rheology; intra-plate volcanism; volcanic islands; seamounts; small-scale convection

Lay Summary (English)

Lead
Lay summary
Oceanic plates are covered with numerous volcanic islands and seamounts. One cause of these volcanic islands is believed to be hot plumes, which upwell from deep in the mantle and cause volcanic island chains such as the Hawaii-Emperor chain. Such island chains, or hotspot tracks, are recognized by a volcanic age progression that define the absolute motion and direction of the oceanic plate. Other linear volcanic features do not share the characteristics of hotspot tracks, and different mechanisms have to be invoked to explain those lineations. In this project we study an alternative mechanism for the formation of volcanic islands or volcanic island chains. This alternative mechanism is small-scale convection beneath the oceanic lithosphere.

Small scale convection has been proposed as a possible mechanism to explain these lineations, but up to date this mechanism has not been tested quantitatively. We are investigating this mechanism with a 3-D numerical model that combines realistic rheologies in an oceanic setting with buoyant decompression melting. The driving and resistive forces we are exploring include thermal boundary layer instability and density and viscosity changes associated with melting. Latent heat loss due to melting reduces temperature and thus reduces thermal buoyancy, and increases viscosity. On the other hand, melting also changes the composition of the residue and impregnates the mantle with partial melt, both of which enhance the buoyancy of the mantle. Furthermore we are studying the influence of rheology and melting models on the planform and propagation of such volcanic chains.

To test the models, predictions are being compared with observations: e.g. the size, rate of lengthening, and ages of the volcanic chains, the timing of hotspot-related secondary volcanism and lithospheric thinning, and gravity, topography and volumes of volcanism.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
107995 The role of small-skale convective instabilities at oceanic intra-plate volcanism 01.07.2005 Project funding

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