Astrid Ridge is an

undersea ridge 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 diverge ...

on the continental margin of

Dronning Maud Land Queen Maud Land ( no, Dronning Maud Land) is a roughly region of Antarctica claimed by Norway as a dependent territory. It borders the claimed British Antarctic Territory 20° west and the Australian Antarctic Territory 45° east. In addit ...

East Antarctica East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains. It lies almost ...

. It is present on the

GEBCO The General Bathymetric Chart of the Oceans (GEBCO) is a publicly available bathymetric chart of the world's oceans. The project was conceived with the aim of preparing a global series of charts showing the general shape of the seafloor. Over the ...

5th edition charts. The name was approved by the

Advisory Committee for Undersea Features The United States Board on Geographic Names (BGN) is a federal body operating under the United States Secretary of the Interior. The purpose of the board is to establish and maintain uniform usage of geographic names throughout the federal governm ...

in June 1987. The ocean along the continental margin of Dronning Maud Land, the Riiser-Larsen and Lazarev seas, are dominated by three topographic features: Astrid Ridge,

Maud Rise Maud Rise () is an oceanic plateau, which rises, at its shallowest, to depths of about a 1,000 meters. It is located in the Weddell Sea in the Southern Ocean. Its name was approved by the Advisory Committee for Undersea Features in June 1987. Geo ...

, a large volcanic plateau in the Lazarev Sea (3°E, 65°S), and

Gunnerus Ridge Johan Ernst Gunnerus (26 February 1718 – 25 September 1773) was a Norwegian bishop and botanist. Gunnerus was born at Christiania. He was bishop of the Diocese of Nidaros from 1758 until his death and also a professor of theology at the Unive ...

(33.5°E), probably underlain by

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' be ...

. Astrid Ridge, extending from 65°S to the Antarctic margin and located between 9°E and 17°E, forms the eastern border of the Lazarev Sea and the western border of the Riiser-Larsen Sea. It is divided into two parts by the Astrid Fracture Zone: south of 67°S Astrid Ridge stretches N-S while the northern part follows the SW—NE direction of the fracture zone. The geological evolution of the Astrid Ridge remains enigmatic. The Riiser-Larsen Sea is a conjugate basin to the

Mozambique Basin Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

(in the ocean east of southern Africa) and the two once formed the first ocean to open during the break-up of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

. Astrid Ridge is a large volcanic features closely related to this 160 Ma break-up during which

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 ...

began to form in the Riiser-Larsen Sea. West of Astrid Ridge, however, neither oceanic crust nor

magnetic anomalies In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying ...

have been found and this area is therefore interpreted as stretched continental crust and Astrid Ridge as a former continental margin created by volcanism during the break-up.

References

; Notes ; Sources * * Ridges of Queen Maud Land Princess Astrid Coast {{PrincessAstridCoast-geo-stub