The Mid-Cayman Rise or Mid-Cayman Spreading Center is a relatively short (110 km long)

divergent plate boundary In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent b ...

in the middle of the

Cayman Trough __NOTOC__ The Cayman Trough (also known as the Cayman Trench, Bartlett Deep and Bartlett Trough) is a complex transform fault zone pull-apart basin which contains a small spreading ridge, the Mid-Cayman Rise, on the floor of the western Caribbea ...

. It forms part of a dominantly

transform boundary A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...

that is part of the southern margin to the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...

. It is an ultra-slow spreading center with an opening rate of 15–17 mm per year.

Formation

The Mid-Cayman Rise developed during the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

when the northern part of the

Caribbean Plate The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America. Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders ...

collided with the Bahamas Platform, forcing the southern boundary to propagate southwards. This boundary initially formed as two strike-slip faults with a large left-stepping offset between them, generating a pull-apart basin. Continuing movement on the boundary and extension within the pull-apart led to the formation of an area of

oceanic crust Oceanic 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 ultramafic cumu ...

containing a north-south trending

spreading center A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a diver ...

that remains active to the present day. When the spreading center formed, all the displacement on the Swan Islands Transform Fault was transferred by the Mid-Cayman Rise to the

Septentrional-Oriente fault zone The Septentrional-Orient fault zone (SOFZ) is a system of active coaxial left lateral-moving strike slip faults that runs along the northern side of the island of Hispaniola where Haiti and the Dominican Republic are located and continues along ...

. During the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

, the leading edge of the Caribbean Plate began to collide with the Bahamas Platform. This led to the development of a new fault system, formed of the

Walton fault zone The Walton fault zone is a major active left lateral (sinistral) strike-slip fault, forming part of the southern boundary to the Cayman Trough. It extends from the Mid-Cayman Rise spreading center in the west to Jamaica in the east. It has a total ...

and the

Enriquillo–Plantain Garden fault zone The Enriquillo–Plantain Garden fault zone (EPGFZ or EPGZ) is a system of active coaxial left lateral-moving strike slip faults which runs along the southern side of the island of Hispaniola, where Haiti and the Dominican Republic are located ...

, carrying some of the plate boundary displacement and creating the

Gonâve Microplate Gonave may refer to: *Gulf of Gonâve *Gonâve Island * Gonâve Microplate See also *Gonaïves Gonaïves (; ht, Gonayiv, ) is a List of communes of Haiti, commune in northern Haiti, and the capital of the Artibonite (department), Artibonite Depa ...

. Eventually all the displacement on the plate boundary is expected to move onto the southern fault system as the microplate becomes accreted to the North American Plate, at which point the Mid-Cayman Rise will become extinct.

Hydrothermal Vents

The Mid-Cayman Rise is a particularly unique location as there are two confirmed

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

fields in close proximity of each other. The Von Damm vent field, named after geological oceanographer Karen Von Damm, is located on the ocean core complex Mount Dent, and features unique chimney structures of

talc Talc, or talcum, is a Clay minerals, clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thi ...

. The Beebe Vent field, after

William Beebe Charles William Beebe ( ; July 29, 1877 – June 4, 1962) was an American naturalist, ornithologist, marine biologist, entomologist, explorer, and author. He is remembered for the numerous expeditions he conducted for the New York Zoological ...

, is the world's deepest hydrothermal system with extremely hot vent fluids. There is activity in the water column to suggest a third vent field, though it has not yet been identified.

References

{{Reflist Geology of the Caribbean