Atlantis Massif
Encyclopedia
The Atlantis Massif is a prominent undersea massif
, a dome-shaped region approximately 10 mi. (16 km) across and rising about 14,000 ft. (4250 m) from the sea floor, in the North Atlantic Ocean
. It is located at approximately 30°8'N latitude 42°8'W longitude; just east of the intersection of the Mid-Atlantic Ridge
with the Atlantis Transform Fault. The highest point of the massif is approximately 700 m beneath the surface.
The massif was formed approximately 1.5-2.0 million years ago. Geologic studies of the massif have indicated that it is not composed of the black basalt
typical of the ocean floor, but rather of dense green peridotite
usually found in the mantle. The central dome is corrugated and striated in a way that is representative of an exposed ultramafic oceanic core complex. It is believed that the massif was formed underneath the nearby Mid-Atlantic Ridge but was pulled underneath the ridge during the movement of the plates
.
The Lost City hydrothermal field
, discovered in 2000, is near the summit of the ridge.
An expedition to the area in 1996 made an important advance in the study of the ocean floor. It found that a steeply sloping detachment fault
is associated with the oceanic core complex structure. The dome was caused by mantle material being extruded to the surface.
Massif
In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...
, a dome-shaped region approximately 10 mi. (16 km) across and rising about 14,000 ft. (4250 m) from the sea floor, in the North Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. It is located at approximately 30°8'N latitude 42°8'W longitude; just east of the intersection of the Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...
with the Atlantis Transform Fault. The highest point of the massif is approximately 700 m beneath the surface.
The massif was formed approximately 1.5-2.0 million years ago. Geologic studies of the massif have indicated that it is not composed of the black basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
typical of the ocean floor, but rather of dense green peridotite
Peridotite
A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...
usually found in the mantle. The central dome is corrugated and striated in a way that is representative of an exposed ultramafic oceanic core complex. It is believed that the massif was formed underneath the nearby Mid-Atlantic Ridge but was pulled underneath the ridge during the movement of the plates
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
.
The Lost City hydrothermal field
Lost City (hydrothermal field)
Lost City is a field of hydrothermal vents in the mid-Atlantic ocean that differ significantly from the black smoker vents found in the late 1970s. The vents were discovered in December 2000 during a National Science Foundation expedition to the mid-Atlantic. A second expedition mounted in 2003...
, discovered in 2000, is near the summit of the ridge.
An expedition to the area in 1996 made an important advance in the study of the ocean floor. It found that a steeply sloping detachment fault
Detachment fault
Detachment faulting is associated with large-scale extensional tectonics. Detachment faults often have very large displacements and juxtapose unmetamorphosed hanging walls against medium to high-grade metamorphic footwalls that are called metamorphic core complexes...
is associated with the oceanic core complex structure. The dome was caused by mantle material being extruded to the surface.
