Geology & Geophysics Group
The Axial Volcanic Ridges Programme
Contact: Dr Bramley Murton
Mid-ocean ridges (MORs) are the loci of the most voluminous volcanism on our planet, the products of which have generated 60% of the Earth’s surface crust. Unlike its sub-aerial counterpart, MOR volcanism is hidden from view beneath several kilometres of water, leaving the processes largely unknown. For many MORs, this volcanism forms axial volcanic ridges (AVRs Figure 1), a few kilometres wide and tens of kilometres long, which appear episodic or cyclic in their evolution (Figure 2). Although the processes that generate AVRs, their episodicity, effusion rates and links to melt extraction from the Earth’s mantle are the focus of much speculation, little is known in sufficient detail to unravel their evolution. This is largely because we have not had the tools capable of studying volcanic architecture, sampling volcanic stratigraphy or determining age relationships between erupted units at the fine scale required.
Above right: Part of AVR at MAR 45°N. Bathymetry, 2300 m (green) to 3600 m (purple), contour interval 50 m, illuminated from NW. AVR runs NNE through centre of figure. Features, marked by letter to their immediate left, are: F, flat-topped volcano; H, hummocky volcano; R, fissure ridges; S, lateral spurs; T, lava terraces. Flat-lying areas L are probable sites of smooth lava flows.
In recent years a new generation of submersible instruments has been developed that now allow us to address AVR genesis directly. Recent developments in dating techniques, coupled with improvements in the precision of geochemical analyses, now provide the means to test many of the models describing MOR volcanism.
Left: Model of AVR evolution
During 2008, we will make a detailed study from our new research vessel, the James Cook. We will make extensive use og the UK’s deep-ocean ROV, ISIS, to deploy new high-resolution imaging and sampling tools. From a combination of geophysics, geochemistry and with high-precision uranium series dating, we will unravel the complex evolution of MOR volcanism.
This study will yield new insights into the transient processes of melt genesis, migration, storage, extraction and eruption, and will enable the relationship of MOR volcanism to hydrothermal activity, chemosynthetic biodiversity and ocean chemical cycles to be quantitatively assessed. These insights are essential if we are to understand this key component of the Earth System – and hence its relationship to Earth evolution as a whole.
Right: The new RV James Cook and the ROV ISIS.
Download the Axial Volcanic Ridges Study Programme outline (Adobe PDF, 0.6MB)
