877 articles
Mascarene Basin
Mascarene Basin, ocean basin of the western Indian Ocean east of Madagascar; extinct spreading ridge active about 84–60 Ma between India and Madagascar, succeeded by the Carlsberg Ridge.
Mascarene Plateau
The Mascarene Plateau is an arcuate submerged seafloor high in the southwestern Indian Ocean, extending over 2,300 km from the Seychelles to Mauritius, with shallow banks hosting the world's largest contiguous seagrass beds.
Mason Inlet
Mason Inlet is an Antarctic inlet on the Black Coast, Palmer Land, between Cape Herdman and Cape Mackintosh at 72°53'S 60°15'W, named for FIDS surveyor Douglas Percy Mason and fed by Clowes and Watkins glaciers.
Massachusetts Bay
Massachusetts Bay is an Atlantic bay at the southern end of the Gulf of Maine between Cape Ann and Cape Cod, namesake of the 1628 Massachusetts Bay Company and Colony, with semidiurnal tides, Stellwagen Bank, and 12,000 years of Native habitation.
Matagorda Bay
Matagorda Bay is a large estuary on the central Texas Gulf coast, fed by the Lavaca and Colorado Rivers and sheltered from the Gulf by Matagorda Peninsula.
Matha Strait
Matha Strait (Estrecho Matha) is a deep, navigable NW-SE strait between Adelaide Island and the Biscoe Islands off the Antarctic Peninsula, named for André Matha of Charcot's expedition and renamed from Matha Bay by Rymill's 1934-37 BGLE survey.
Matochkin Strait
Matochkin Strait (Маточкин Шар, Matochkin Shar) is a 2–3 km wide strait separating Severny and Yuzhny islands of Novaya Zemlya, formed along a transverse fault, with Proterozoic basement slices, ca. 700 Ma granites, and nearby underground nuclear testing at Mt. Lasareff.
Maud Rise
Maud Rise, a large volcanic undersea plateau in the eastern Weddell Sea near 66°S 3°E, marked by a Taylor cap circulation, a warm-water Halo, and recurring open-ocean polynyas in the 1970s and 2016–2017.
Maxwell Bay
Maxwell Bay (Fildes Bay), a U-shaped fjord between King George and Nelson Islands, South Shetland Islands, Antarctica; named by Weddell after Francis Maxwell; hosts Chilean, Russian, Korean, and other research stations.
McFarlane Strait
McFarlane Strait: strait between Greenwich and Livingston Islands, South Shetland Islands, Antarctica, near 62°32′S 59°55′W; also called Yankee Sound; named for Captain Andrew McFarlane of the brig Dragon; strong tidal currents make passage hazardous.
McLeod Bay
McLeod Bay names several bays: an official bay on the British Columbia coast (CGNDB key JBKQU), a deep East Arm basin of Great Slave Lake, NWT, a bay on Dall Island, Alaska, and a bay on Gauer Lake, Manitoba.
McMurdo Sound
McMurdo Sound is the Antarctic sound between Ross Island and the mainland, discovered by James Clark Ross in 1841 and named for Lt. Archibald McMurdo. It hosts McMurdo Station and Scott Base, stable fast ice south of 77.6°S, polynyas to the north, and near-freezing waters around -2°C.
Mediterranean Ridge
Mediterranean Ridge: submarine accretionary wedge of the Hellenic subduction zone, where Africa subducts beneath the Aegean at about 40 mm/yr; over 300 km wide, 2,000 km long, fastest growing accretionary complex on Earth, with abundant mud volcanoes and Messinian salt diapirs.
Melville Bay
Melville Bay is a bay on the northwest Greenland coast, named by Sir John Ross in 1818 and protected since 1977 as a nature reserve for narwhal and polar bear habitat, with only quota-regulated traditional narwhal hunting permitted.
Menai Bay Conservation Area
Menai Bay Conservation Area is a 470 km² marine protected area off southwest Unguja, Zanzibar, established in 1997 and the island's largest, home to endangered humpback dolphins.
Messinian salinity crisis
Messinian salinity crisis: late Miocene (5.97–5.33 Ma) isolation of the Mediterranean from the Atlantic, up to 2.5 km drawdown, Mediterranean Salt Giant deposition, Lago-Mare phase, and Zanclean megaflood refilling.
Mexico Basin
Mexico Basin, formerly Sigsbee Deep, is a GEBCO-registered undersea basin in the deep Gulf of Mexico between 22°30′N 95°00′W and 25°00′N 90°00′W; distinct from the landlocked Basin of Mexico.
Mid-Atlantic Ridge
Mid-Atlantic Ridge (MAR): slow-spreading divergent plate boundary down the center of the Atlantic, 87°N to 54°S, 2–5 cm/yr, Grand Canyon-scale rift valley, discovered 1950s, explored by submersible in Project FAMOUS 1974.
Mid-ocean ridge
Mid-ocean ridge: the global chain of underwater volcanic mountains at divergent plate boundaries, about 65,000 km long; new oceanic crust forms by seafloor spreading, with slow ridges like the Mid-Atlantic Ridge showing rift valleys and fast ridges like the East Pacific Rise smooth axial highs.
Middle America Trench
The Middle America Trench is a Pacific Ocean trench off Mexico and Central America where the Cocos and Rivera plates subduct beneath the North American and Caribbean plates.
Middle Passage
The Middle Passage was the middle leg of the triangular Atlantic slave trade, carrying enslaved Africans to the Americas, 1526-1866; about 12.5 million embarked, 10.7 million survived, with roughly 15 percent average voyage mortality.
Mikkelsen Bay
Mikkelsen Bay, Antarctica; also Zaliv Mikkel'sen, Bahía Mikkelsen. A bay 15 mi wide between Bertrand Ice Piedmont and Cape Berteaux, Fallières Coast, Graham Land, named for Danish Arctic explorer Ejnar Mikkelsen, distinct from Mikkelsen Harbour.
Milford Sound
Milford Sound (Piopiotahi) is a 16 km glacial fiord in Fiordland National Park on New Zealand's South Island west coast, within Te Wahipounamu World Heritage area; named by John Grono in 1823, it receives over a million visitors yearly via the Milford Road and Homer Tunnel.
Mill Inlet
Mill Inlet: ice-filled inlet on the east coast of Graham Land, Antarctica, at 67°00'S 064°20'W, receding 8 mi NW between Cape Robinson and Monnier Point; its glaciers feed the Larsen Ice Shelf.
Milne Bay
Milne Bay is a bay and province at the eastern tip of Papua New Guinea, with about 160 islands, 210,000 people, PNG's largest coral reef area, Alotau as capital, and major diving and fisheries economies.
Mindelo
Mindelo is the port city and capital of the island of São Vicente in Cape Verde, an Atlantic archipelago off West Africa, often called the country's cultural capital.
Minto Inlet
Minto Inlet (Kangiryuaqtihuk) is an inlet on western Victoria Island, Northwest Territories, Canada; type locality of the Neoproterozoic Minto Inlet Formation evaporites of the Shaler Supergroup, within the Minto Inlier.
Mobile Bay
Mobile Bay is a shallow estuary on Alabama's Gulf coast, the sixth largest estuary in the continental United States, with the city of Mobile at its head.
Mobiloil Inlet
Mobiloil Inlet, formerly Mobiloil Bay, is an ice-filled inlet on the east coast of Graham Land, Antarctic Peninsula, named by Hubert Wilkins in 1928 after a Vacuum Oil Company lubricant; its head holds the Mercator Ice Piedmont.
Mohns Ridge
Mohns Ridge is an ultraslow-spreading segment of the mid-ocean ridge in the Norwegian-Greenland Sea, extending about 550 km from the Jan Mayen Transform Fault to the Knipovich Ridge.