3,546 articles
Oahu
Oahu (Oʻahu), Hawaii's third largest island and "The Gathering Place," formed by the Waianae and Koolau shield volcanoes; holds Honolulu, about 69% of the state's population, Pearl Harbor, and six traditional moku districts.
Oak Island
Oak Island (Nova Scotia) is a privately owned Mahone Bay island tied to the Money Pit treasure legend dating to 1795; no treasure has been proven, early accounts lack contemporary evidence, and the story is now popularized by The Curse of Oak Island.
Oakhurst Rock Shelter
Oakhurst Rock Shelter is a Later Stone Age archaeological site in a sandstone cliff on the Klein Keurbooms River in South Africa's southern Cape, with about 12,000 years of deposits and 46 burials.
Oceana Nunatak
Oceana Nunatak, one of the sixteen Seal Nunataks, is a volcanic peak at the NW corner of Robertson Island off the east Antarctic Peninsula (65°08'S 59°48'W), discovered by C.A. Larsen in December 1893 and named for the Hamburg Oceana Co.
October Revolution Island
October Revolution Island (Ostrov Oktyabrskoy Revolyutsii), largest island of Severnaya Zemlya, Krasnoyarsk Krai, Russia; 14,200 km², 965 m Mount Karpinsky, over half glaciated, charted 1930–32 by Ushakov and Urvantsev.
Ogilvie Mountains
Ogilvie Mountains (Ogilvie Range): mountain range in Yukon, Canada, extending into Alaska, crossed by the Dempster Highway; named for surveyor William Ogilvie; Proterozoic-Triassic sedimentary rocks, restricted Pleistocene ice caps, endemic collared lemming.
Ogo Mountains
Ogo Mountains (Buuraha Oogo, Oogo), highland belt and dissected plateau in northern Somalia and Somaliland, middle of three topographic zones between the Guban coastal plain and Haud plateau; summits near Erigavo reach about 2,400 m.
Ohlin Island
Ohlin Island, also called Bailys Island, is a 170 m high uninhabited island in the Palmer Archipelago, Antarctica, about 11 km west of Tower Island, discovered by the Swedish Antarctic Expedition 1901–04 and named by Nordenskjöld for zoologist Axel Ohlin.
Ojos del Salado
Nevados Ojos del Salado, on the Chile-Argentina border in the Puna de Atacama, is the world's highest volcano above sea level (6,879-6,893 m), Chile's highest mountain, fumarolically active, last erupting around 750 CE, first climbed in 1937.
Okinawa Island (沖縄)
Okinawa Island (沖縄島, Okinawa-jima), also Okinawa Main Island, is the largest Ryukyu island, Japan: about 1,207 km², 1.35 million people, Naha capital, Ryukyu Kingdom heritage, 1945 battle, US bases.
Okinotorishima (沖ノ鳥島)
Okinotorishima (沖ノ鳥島), also called Parece Vela, is a coral reef about 1,700 km south of Tokyo that is Japan's southernmost island, with only two small islets above sea level.
Oksskolten
Oksskolten (Southern Sami: Uktsiesnjurhtjien åejjie) is a 1,916-meter mountain in Hemnes Municipality, Nordland, Norway, the highest point in Nordland county and in all of Northern Norway.
Ōkunoshima (大久野島)
Ōkunoshima (大久野島), "Rabbit Island," is a small Hiroshima Prefecture island in the Seto Inland Sea, formerly a secret Imperial Japanese Army poison gas plant (1929–1945, ~6,500 tons) and now a tourist site with introduced feral European rabbits.
Öland
Öland (Ölandsbron link) is a 140-km-long Swedish limestone island in the Baltic Sea, home to Stora Alvaret, Europe's largest alvar, and the UNESCO Agricultural Landscape of Southern Öland inscribed in 2000.
Old Harry Rocks
Old Harry Rocks: chalk stacks, arches, and stumps at Handfast Point, Ballard Down, Dorset, eastern end of the Jurassic Coast World Heritage Site; Upper Cretaceous chalk once continuous with the Isle of Wight's Needles.
Old Man of Coniston
Old Man of Coniston, or Coniston Old Man, an 803 m Wainwright fell in the Lake District rising behind Coniston village, known for its copper mines, slate quarries worked since the 13th century, and the popular Low Water and Goat's Water circular walk.
Old Man of the Mountain
The Old Man of the Mountain was a 40-foot granite face profile on Cannon Mountain in Franconia Notch, New Hampshire, the state emblem until its collapse in 2003.
Oldman Formation
The Oldman Formation is a Late Cretaceous sandstone and shale formation in southern Alberta, Canada, named in 1940 and known for its rich dinosaur fossils, including complete skeletons.
Olkaria
Olkaria is a volcanic complex and high-temperature geothermal field south of Lake Naivasha in the Kenya Rift; Africa's leading geothermal field, producing power since 1981 and exceeding 670 MWe.
Olympic Peninsula
The Olympic Peninsula is a roughly triangular peninsula in northwestern Washington, bordered by the Pacific Ocean and the Strait of Juan de Fuca, home to Mount Olympus (7,980 ft), temperate rain forests, Olympic National Park, and eight tribes.
Olympos Oros (Mytikas)
Mytikas (Μύτικας, "nose"), also Pantheon, is the highest peak of Mount Olympus and of Greece at about 2,918 m. First climbed in 1913 by Kakkalos, Boissonnas, and Baud-Bovy; final section is an exposed Class III limestone scramble.
Oman Mountains
Oman Mountains: the mountain system of southeastern Arabia, chiefly the 650 km Al Hajar arc (Jebel Shams, about 3,000 m) plus the monsoon-fed Dhofar ranges, a WWF freshwater ecoregion with wadis and aflaj.
Ometepe
Ometepe (Isla de Ometepe), Nicaragua's 276 km² volcanic island in Lake Cocibolca, formed by active Concepción (1,610 m) and dormant Maderas (1,394 m), a UNESCO biosphere reserve since 2010.
Ontakesan
Ontakesan (御嶽山), or Mount Ontake, is Japan's second highest volcano at 3,067 m on the Nagano-Gifu border, a stratovolcano with phreatic eruptions in 1979, 1991, 2007, and the deadly 2014 eruption that killed about 57 hikers.
Opala
Opala (Опала, Opalskaya Sopka) is an active stratovolcano-caldera complex in southern Kamchatka, Russia, 2,439-2,475 m high, known for its 40,000-year-old caldera, the 1400 cal BP rhyolite eruption, and OP marker tephra.
Orcas Island
Orcas Island, the largest of Washington's San Juan Islands at about 57 square miles, lies in the Salish Sea; its Mount Constitution rises 2,409 feet, and Eastsound is its main village.
Ordos Desert
The Ordos Desert (鄂尔多斯沙漠) is the collective name for the sandy deserts of the Ordos Plateau in Inner Mongolia, China, in the great bend of the Yellow River.
Ore Mountains
The Ore Mountains (Erzgebirge, Krušné hory) are a mountain range on the German-Czech border, mined for silver and other metals from the Middle Ages into the 20th century.
Oregon High Desert Grotto
Oregon High Desert Grotto (OHDG) is a National Speleological Society caving chapter based in Bend, Oregon, publishing the Oregon Underground newsletter and running cave cleanups, graffiti removal, and Glacier Cave Explorers.
Orinoco Llanos
Orinoco Llanos (Llanos del Orinoco), tropical savanna floodplains of Venezuela and Colombia in the Orinoco Basin; second-largest Neotropical savanna over 500,000 km2, seasonally flooded, with 60 endemic fish species and only 5% protected.