The principle objective of the cruise is to investigate the geology of the Marion Rise, a major rise in the sea floor topography associated with an ocean mantle hot spot and compare it to the better known Icelandic Rise on the Atlantic Ridge (fig 1b below). Whereas the latter Rise is commonly believed to be pushed upward by enhanced upward flow from a large mantle plume, and exhibits extensive volcanism, existing data suggest that the Marion Rise is a region of limited volcanism with thin or missing volcanic crust. If this is the case, then mantle flow from the Marion Island mantle hotspot must be limited and cannot support the Marion Rise, which is 1,000 m deeper in water depth, but a thousand kilometers longer than the Icelandic Rise, bringing into question the hypothesis that ocean rises are pushed upwards by rising mantle plumes.

Additional objectives include investigating the tectonics and morphology of adjacent sections of the SW Indian Ridge which show contrasting symmetric and oblique spreading (fig b below). The latter is believed to be associated with amagmatic spreading with very little volcanism.