Minerals Report - International Seabed Authority

East Pacific Ocean), Central Mid-Atlantic Ridge and South West Indian Ridge
(Figure 3).
Figure 3. Plot of incidence of hydrothermal plume activity (i.e. what proportion of any midocean
ridge section is overlain by a detectable neutrally-buoyant hydrothermal plume) versus
full spreading rate for all of: the central Mid-Atlantic Ridge (MAR); the Juan de Fuca Ridge
(JdF), the North East Pacific Rise (NEPR) and the South East Pacific Rise (SEPR). After
Baker et al. [4, 28].
3.2 Secondary effects: Ridge Segmentation and Hot Spots
Although spreading rate can account for much of the variability seen
in the abundance of hydrothermal venting worldwide, it cannot explain
everything. In recent work, we have studied the incidence of hydrothermal
activity along three different sections of the Mid-Atlantic Ridge between
Iceland and the equator, which exhibit markedly different abundances of
venting, all at the same spreading rate. The first section, between
approximately 15°N and 30°N exhibits approximately one vent site every 100-
150km along axis, consistent with the predictions from spreading rate alone
(Figure 4).
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