2,436 articles
Malheur
Malheur refers to a freshwater lake in Harney Basin, Oregon, and surrounding features like the wildlife refuge. It is the northernmost internally draining basin in the Great Basin.
Malili Lakes
The Malili Lakes are five interconnected ancient lakes in central Sulawesi, Indonesia, comprising Matano, Mahalona, Towuti, Lontoa, and Masapi, holding endemic species flocks of fishes, snails, shrimps, and crabs.
Mamoré
Mamoré River (Río Mamoré), Bolivian-Brazilian white-water river, about 1,930 km long, formed by the Chaparé and Ichilo rivers; joins the Beni to form the Madeira, a major Amazon tributary.
Mamore - Madre de Dios Piedmont
Mamore - Madre de Dios Piedmont, FEOW freshwater ecoregion 318, upper Madeira headwaters in Bolivia, Peru, and Brazil; whitewater Beni, Mamoré, and Madre de Dios rivers, about 80 endemic fish, and mercury contamination from gold mining.
Man Drowned Himself Lake
Man Drowned Himself Lake is an official lake in the Mackenzie district, Sahtu region, Northwest Territories, Canada, at 65.6932° N, 123.2143° W, about 9 km long, named for a recorded drowning.
Manawatū River mouth and estuary
Manawatū River mouth and estuary (Manawatū Estuary), a 200-plus-hectare bar-built estuary at Foxton Beach, New Zealand; Ramsar site no. 1491 (2005), famed for 95 bird species, migratory bar-tailed godwits, and wrybills.
Mangrove
Mangroves are about 80 species of salt-tolerant trees and shrubs of the tropical and subtropical intertidal zone, forming forests that store over 6.23 gigatonnes of carbon, protect coastlines, and support fisheries; global extent was 147,283.64 km² in 2025.
Mangrove swamp
Mangrove swamp: a tropical and subtropical intertidal coastal wetland dominated by salt-tolerant mangrove trees, about 80 species, 14.8 million hectares globally, defined by tidal flooding, salt adaptations, blue carbon storage, and coastal protection.
Manicouagan Reservoir
Manicouagan Reservoir (Réservoir Manicouagan, Innu Manikuakan), the 'Eye of Québec', is a 1,940 km² ring-shaped hydroelectric reservoir in Québec filling the annular moat of a ~214-million-year-old impact crater, dammed by Hydro-Québec's Daniel-Johnson Dam in the 1960s.
Manihiki Plateau
The Manihiki Plateau is a large oceanic plateau in the central Pacific Ocean east of the Ontong Java Plateau, formed by massive Early Cretaceous volcanism about 120 million years ago.
Manikaran
Manikaran: pilgrimage village in Parvati Valley, Kullu district, Himachal Pradesh, India, famed for hot springs up to 97 °C, Gurudwara Manikaran Sahib where langar cooks in spring water, and a 5 kW pilot geothermal plant.
Manila Bay
Manila Bay (Look at the bay, Look at Manila) is a semi-enclosed estuary and natural harbor on Luzon, Philippines, site of Dewey's 1898 defeat of the Spanish fleet, 1944 fighting, and modern reclamation and rehabilitation programs.
Manoa Falls Trail
Mānoa Falls Trail is a 1.6-mile easy rainforest hike in Honolulu Watershed Forest Reserve, Oʻahu, ending at a 150-foot waterfall; managed by Nā Ala Hele, free entry, $7 Paradise Park parking, no swimming, reopened 2021 after refurbishment.
Manus Basin
Manus Basin: actively spreading back-arc basin in the eastern Bismarck Sea, Papua New Guinea, between fossil Manus Trench and active New Britain Trench; opens ~10 cm/yr, hosts Pacmanus, Vienna Woods, Solwara 1 hydrothermal sulfide deposits.
Maquan
Maquan (Maquan Tsangpo, Maquan River, Tachog Khabab), the ~270 km Tibetan headwater branch of the Yarlung Tsangpo (upper Brahmaputra) in Burang and Saga counties, rising from Himalayan glaciers at over 5,200 m.
Mar Chiquita
Mar Chiquita (Mar de Ansenuza), Córdoba, Argentina: South America's largest saline lake, a closed endorheic basin fed by the Dulce, Suquía, and Xanaes rivers; salinity 28–360 g/L, Ramsar site, Ansenuza National Park. Distinct from the Buenos Aires coastal lagoon of the same name.
Mar Chiquita - Salinas Grandes
Mar Chiquita (Mar de Ansenuza) is Argentina's largest saline lake, a closed-basin lake in Córdoba fed mainly by the Dulce River; Salinas Grandes and Salinas de Ambargasta are its neighboring dried salt flats.
Marais poitevin
Marais poitevin is a man-made wetland in western France, reclaimed from the former Gulf of Pictons; at about 100,000 hectares it is France's second largest wetland.
Marajó Bay
Marajó Bay (Baía de Marajó), a roughly 4,500 km2 tide-dominated estuary in Pará, Brazil, southwest of Marajó Island near Belém, fed mainly by the Pará and Tocantins rivers, muddy year-round, shallow, and a key artisanal fishing ground.
Marañón River
The Marañón River (Río Marañón) is a ~1,400 km Peruvian river whose confluence with the Ucayali forms the Amazon; it supplies about 10% of the Amazon's discharge, was long considered its source, and faces major dam proposals.
Mare Nostrum
Mare Nostrum, Latin for 'our sea', was the Roman name for the Mediterranean Sea, revived by Fascist Italy as imperial rhetoric and reused for Italy's 2013-2014 migrant search-and-rescue naval operation.
Marguerite Bay (landform)
Marguerite Bay, a large bay on the western Antarctic Peninsula at 68°30′S 68°30′W, discovered and named by Charcot in January 1909; known for raised beaches, a 1,600 m deep trough, Rothera Research Station, and the Wordie Ice Shelf.
Marine Atlantic
Marine Atlantic Inc. (Marine Atlantique), Canadian federal Crown corporation since 1986 (formerly CN Marine) operating the constitutionally required North Sydney–Port aux Basques ferry and seasonal Argentia route with four ice-class vessels.
Marine channel
Marine channel: a waterway deep enough for navigation through otherwise shallow or obstructed water, either a natural sea passage like the English Channel or a dredged lane such as the Ambrose and Savannah shipping channels; also submarine channels carved by turbidity currents.
Marine life of the Indian Ocean
The marine life of the Indian Ocean is the fish, corals, mammals, and other fauna of the 70 million km² basin between Africa, Asia, and Australia.
Marine life of the Mediterranean Sea
The marine life of the Mediterranean Sea comprises about 17,000 recorded species, with the small, nutrient-poor sea supporting 4–18% of the world's marine biodiversity, including bluefin tuna spawning grounds and the threatened Mediterranean monk seal.
Marismas Nacionales
Marismas Nacionales: Mexican Pacific wetland complex in Sinaloa and Nayarit; Ramsar site 732 (1995, 200,000 ha) and Nayarit Biosphere Reserve (2010); seven rivers, vast mangroves, and hundreds of thousands of migratory birds.
Maritime chokepoint
A maritime chokepoint is a narrow sea channel critical to international trade and energy security, such as Hormuz and Malacca, whose closure forces ships onto much longer, costlier detours.
Maritsa (Марица)
Maritsa (Марица; Evros, Meriç; ancient Hebros), 537 km Balkan river rising in the Rila Mountains, flowing through Bulgaria, Greece, and Turkey to the Aegean, a flood-prone transboundary border river.
Markermeer & IJmeer
Markermeer & IJmeer: shallow freshwater lakes in the central Netherlands, created in 1976 by the 26 km Houtribdijk; IJmeer is the southern part. Natura 2000 and Ramsar site 1245, 68,463 ha, turbid silt bed, Marker Wadden restoration.