The mid-ocean ridge system is the longest continuous feature of the Earth's surface and is where all of the ocean floor is created with volumes of seafloor volcanism vastly exceeding that of any type of volcano on land. It provides the means for much of the heat loss from the interior of the Earth, a large part of which is carried by flowing sea water that moves through the rocks of the seafloor. Chemicals as well as heat are extracted by this process leading to spectacular areas of hydrothermal venting on the seabed at the ridge axis with seafloor sulphide deposits and biological communities. The process affects (some say controls) ocean chemistry and global climate.

In recent years, the recognition that a major coordinated effort was needed in order to understand the fundamental dynamical processes operating at mid-ocean ridges led the scientific community to mount a series of major national and international programmes. The major UK component of this effort has been the British Mid-Ocean Ridge Initiative (BRIDGE) which was established as a NERC Community Research Project, and many other countries have active programmes in this area of science. For this reason a Royal Society Discussion Meeting was organized by the editors and this was held in London on 6 and 7 March 1996. Much of the work presented at the Discussion Meeting has been the product of these initiatives. In addition, a poster session held concurrently with the meeting highlighted achievements of the BRIDGE programme.