Mid-ocean Ridges

Abstract

Mid-ocean ridges illustrate well how volcanic, tectonic, hydrothermal and sedimentary processes sculpt geomorphology in the deep ocean. Because of their poor accessibility (lying 2700 m below sea level on average) and remote locations, the development and deployment of new technology has been important for the discovery and investigation of new features. In contrast with continental environments, erosion has only modestly affected these areas, so features can be well preserved, in particular, volcanic landforms. The eruption of lavas creates volcanic cones, ridges of hummocky flows, widespread low-relief flows and drain-back features in lava lakes. Plate-tectonic extension creates faults, many with moderate dips, as inferred from the earthquakes they produce. However, other faults with presently shallower dips are suggested by corrugated slip surfaces exposed at the seabed on slow-spreading ridges. Steep scarps, comprising fractured rock and in places weak lithologies such as serpentinite, are easily destabilized, producing landslides, talus cones and talus ramps. Seawaters penetrating the crust and heated by it produce hydrothermal springs, such as spectacular “black smokers”. Precipitation of sulphides from those exhaling fluids and their deposition produces smooth mats of sediment and chimneys that can collapse to contribute to the sedimentary deposits as talus. This combination of processes makes mid-ocean ridges fascinating environments to work on, representing how >60% of Earth’s solid (oceanic) crust has been created. Despite poor accessibility of such areas, researchers will likely continue to deploy new instruments as they are developed to reveal more details of mid-ocean ridge geomorphology and understanding of how it develops.