The ocean province ranges from shallow coastal areas to the deepest ocean environments. Many of the ocean features have been named and the particular provinces described. The major features are discussed in the following sections.
The rift valley along the center of the rise is a zone of shallow earthquakes. The system is not restricted to the oceans -- it emerges in continental areas in Africa, California, and in Iceland . Numerous open fissures have been observed and mapped in the rift valleys, which is evidence that the crust is being pulled apart along the ridge. The eruption of lava from these fractures parallels the rift valley and creates long narrow ridges.
The oceanic ridge is cut by faults normal to the ridge. Although these are strike-slip faults, vertical displacement may form abrupt cliffs that can be traced for many kilometers . Horizontal movement on these transform faults is on the order of 1-2 cm/yr and the faults are marked by earthquake activity and vulcanism. The magnitude of the system and its nature indicates that it is related to major events and sources of energy in the Earth's interior.
A flat featureless surface known as an abyssal plain occurs when the hilly sea floor has been covered by a thick fill of sediments, which were deposited by turbidity currents. These river-like flows of a sediment water mix are carried along the sea floor. They receive sediments from continental margin submarine canyons which act as conduits for turbidity current transport. The original irregular surface of a volcanic province remains under the turbidite fill. These plains, which may slope less than 1:8000, are found adjacent to land masses -- extending from the continental rise to the abyssal hills. On prominences that rise above the plain, only sediments settling in the water column (pelagic deep-sea sediments) occur. On the surface of the plain, the pelagic sediments are interbedded with a dominating sequence of sands, silts, and clays of terrigenous origin that can be identified as turbidites by displaced benthic fauna and sediment patterns characteristic of turbidites.
Guyots and seamounts are geomorphic forms developed from submarine volcanoes. Seamounts and guyots are isolated, but they do lie in chains or provinces of volcanic activity. They are found in all oceans, but more have been recorded in the Pacific Ocean. The distribution that has been mapped may represent a small percent of the total number since they are only noted where crossed during bathymetric profiling. The seamount is a relatively isolated elevation of the seafloor of more than 1000 meters height, with a small rounded top -- a volcano that did not reach the sea surface. Guyots are drowned volcanic islands that did not become coral atolls. They were planed flat by wave action when at shallow depths, after which subsidence occurred so that they are like seamounts but with a flattened top that lie more than 200 meters below the surface. Although some coral rubble may be found on guyots, they are abrasional platforms that have subsided as a result of isostatic adjustment, with some contributing effect from sea level change.