Seafloor spreadingSeafloor spreading, or seafloor spread, is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. History of studyEarlier theories by Alfred Wegener and Alexander du Toit of continental drift postulated that continents in motion "plowed" through the fixed and immovable seafloor.
Mid-ocean ridgeA mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.Fracture zoneA fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on either side of an active transform fault move in opposite directions, resulting in strike-slip activity.
Mid-Atlantic RidgeThe Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates North America from the Eurasian plate and the African plate, north and south of the Azores triple junction. In the South Atlantic, it separates the African and South American plates.
Rift valleyA rift valley is a linear shaped lowland between several highlands or mountain ranges produced by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear depression may subsequently be further deepened by the forces of erosion. More generally the valley is likely to be filled with sedimentary deposits derived from the rift flanks and the surrounding areas. In many cases rift lakes are formed.
Plate tectonicsPlate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century.
Accretion (geology)In geology, accretion is a process by which material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses. The added material may be sediment, volcanic arcs, seamounts, oceanic crust or other igneous features. DescriptionAccretion involves the addition of material to a tectonic plate via subduction, the process by which one plate is forced under the other when two plates collide.
Oceanic crustOceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramaficcumulates. The crust lies above the rigid uppermost layer of the mantle. The crust and the rigid upper mantle layer together constitute oceanic lithosphere.
São Miguel IslandSão Miguel Island (pronounced; Portuguese for 'Saint Michael'), nicknamed "The Green Island" (Ilha Verde), is the largest and most populous island in the Portuguesearchipelago of the Azores. The island covers 760 km (290 sq mi) and has around 140,000 inhabitants, with 45,000 people residing in Ponta Delgada, the archipelago's largest city.
SubmersibleA submersible is an underwater vehicle which needs to be transported and supported by a larger watercraft or platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent operation at sea. There are many types of submersibles, including both human-occupied vehicles (HOVs) and uncrewed craft, variously known as remotely operated vehicles (ROVs) or unmanned underwater vehicles (UUVs).
Echo soundingEcho sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; the resulting time of flight, along with knowledge of the speed of sound in water, allows determining the distance between sonar and target.
AzoresPortuguese archipelago in the North AtlanticAutonomous Region of Portugal and outermost region of the European UnionThe Azores, officially the Autonomous Region of the Azores, is an archipelago of Portugal, in the Atlantic Ocean, about 1,400 km (870 miles) west of the Portuguese mainland. Politically and administratively, together with Madeira, it is one of the two autonomous regions of Portugal and a special territory of the European Union.*As an Amazon Associate I earn from qualifying purchases.