Detection of hydrothermal plumes on the northern Mid-Atlantic Ridge: results from optical measurements

Several water column surveys conducted on the northern Mid-Atlantic Ridge have been instrumental in the discovery of three new hydrothermal venting sites, and seven other active segments. Hydrothermal sources have yet to be pinpointed in six of these segments. In this study, the observed frequency of high-temperature venting from 23°N to 41°N on the Mid-Atlantic Ridge (MAR), a distance of approximately 1900 km, is one venting system per 150 km of ridge. Combining these data with those of other investigators for the region from 12°N to 41°N leads to an approximate venting frequency of one site per 90 km of ridge, although venting frequencies on sections of the MAR within this region are as high as one site per 25 km. To support this frequency of venting, and considering the larger dimensions of the MAR rift valley, the ratio of axial to off-axis heat loss must be higher on the MAR than on faster spreading ridges.