Geology & Geophysics Group
Mid-Atlantic Ridge: Lucky Strike
Contact: Dr Bramley Murton
Evolution of explosive seamount volcanism: evidence from 37ºN on the Mid Atlantic Ridge
The Lucky Strike segment of the slow-spreading Mid-Atlantic Ridge is characterised by an unusually large central volcanic complex with a history of explosive eruption and hydrothermal activity. This ~65km long, second order ridge segment is centred on 37°17.5'N and 32°16.5'W. At its deepest ends, the segment is ~3200m deep.
Bathymetry and sidescan sonar imagery together reveal a slow-spreading ridge segment that has a large composite volcanic plateau at its centre (see figure below). The central volcanic complex that comprises up to seven constructional terraces with three conical edifices at its highest point in the centre. The three volcanic cones are relatively old and comprise late-stage fractionated and highly vesicular basalt. The presence of hyaloclastites associated with these cones indicates explosive submarine activity. Brittle tectonic deformation in the form of fault scarps has recently bifurcated the central volcanic plateau and post-dates the three central cones.
The central volcanic complex is a composite feature that is the result of an interplay between brittle tectonics and volcanic activity linked to magma evolution and changes in styles of eruption. From the evidence collected from the lucky Strike segment, a model is emerging for the eruptive style, based on mechanisms of magma buoyancy to control the maximum height of the central volcanic complex. The model also invokes magma stagnation, replenishment and assimilation of altered volcanic crust to enhance volatile concentrations in late stage activity, resulting in explosive hydroclastic eruption patterns.
Above left: multibeam bathymetry data (100m grid) for the Lucky Strike central volcanic complex (red colour = shallow). Above right: multibeam bathymetry enhanced by using TOBI sidescan sonar to interpolate depths (on a 6m grid) based on models that relate backscatter intensity to seafloor slope.
