Nauru Nauru ( or ; na, Naoero), officially the Republic of Nauru ( na, Repubrikin Naoero) and formerly known as Pleasant Island, is an island country and microstate in Oceania, in the Central Pacific. Its nearest neighbour is Banaba Island in Ki ...

is positioned in the Nauru Basin of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

, on a part of the

Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

that formed at a

mid oceanic 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 ...

at 132 Ma. From mid

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

(35 Ma) to

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

times a

submarine volcano Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. The volcanoes at mid-ocean ridges ...

built up over a hotspot, and formed a

seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

composed of

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

. The seamount rises over 4300 m above the ocean floor. This hotspot developed simultaneously with a major Pacific Plate reorganisation. The volcano was eroded to sealevel and a

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

atoll An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gr ...

grew on top to a thickness of about 500 m. Coral near the surface has been dated from 5 to 0.3 Ma. The original limestone has been

dolomitised Dolomitization is a geological process by which the carbonate mineral dolomite is formed when magnesium ions replace calcium ions in another carbonate mineral, calcite. It is common for this mineral alteration into dolomite to take place due to ev ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

from

sea water Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approx ...

. The coral was raised above sea level about 30 m, and is now a dolomite limestone outcrop which was eroded in classic

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

style into

pinnacle A pinnacle is an architectural element originally forming the cap or crown of a buttress or small turret, but afterwards used on parapets at the corners of towers and in many other situations. The pinnacle looks like a small spire. It was mainly ...

s up to 20 m high. To at least a depth of 55 m below sea level, the limestone has been dissolved forming cavities, sinkholes and caves. The island was a

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...

rookery A rookery is a colony of breeding animals, generally gregarious birds. Coming from the nesting habits of rooks, the term is used for corvids and the breeding grounds of colony-forming seabirds, marine mammals (true seals and sea lions), and ev ...

and depressions on the surface of the island were filled by a

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...

rich

guano Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant growth. G ...

layer up to several metres thick.

Anibare Bay Anibare Bay is a large bay located in the Anibare District of eastern Nauru island. Physical features It is bordered by capes to the north and south, in Ijuw and Meneng districts respectively. Its Anibare Beach is in excess of two kilometers ...

was formed by the underwater collapse of the east side of the volcano. The collapse formed an amphitheatre shape with the arc shaped block rotating outwards at its base from about 900 to 1100 m below sea level. Below 1100 m the slip bulges out down to 2000 m deep. In

Ijuw District Ijuw is a district in the country of Nauru, located in the northeast of the island. The area covers 1.1 km2 and has a population of 180, making Ijuw the least populated district in the country. Geography Ijuw borders Anabar District to the ...

to the north of the bay there are

lineament ''See also Line (geometry)'' A lineament is a linear feature in a landscape which is an expression of an underlying geological structure such as a fault. Typically a lineament will appear as a fault-aligned valley, a series of fault or fold-aligne ...

s trending inland to the north west.

Buada Lagoon Buada Lagoon is a landlocked, slightly brackish, freshwater lake of Buada District in the island nation of Nauru. It occupies about . The lagoon is classified as an endorheic lake, meaning there is no outflow to other bodies of water such as ...

was formed by solution of the limestone when the sea level was lower, followed by collapse. Nauru is moving at 104 mm per year to the north west along with the underlying Pacific Plate. Streams and rivers don't exist in Nauru. Water is gathered from roof catchment systems. Water is brought to Nauru as ballast on ships returning for loads of

. Fresh water can be found in Buada Lagoon, and also in some brackish ponds at the escarpment base in Ijuw and

Anabar Anabar may refer to: * Anabar Bay, Laptev Sea * Anabar Constituency, Nauru * Anabar District, Nauru * Anabar District, Russia, Sakha, Russia * Anabar Highway, Russia * Anabar Plateau, Russia * Anabar (river), Sakha, Russia * Anabar Shield Anabar ...

in the northeast. There is an underground lake called

Moqua Well The Moqua Well is a small underground lake, in Nauru. History During World War II, Moqua Well was the primary source of drinking water for inhabitants of Nauru.Moqua Caves The Moqua Well is a small underground lake, in Nauru. History During World War II, Moqua Well was the primary source of drinking water for inhabitants of Nauru.Phosphate mining in Nauru The economy of Nauru and Banaba has been almost wholly dependent on phosphate, which has led to environmental catastrophe on these islands, with 80% of the islands’ surface having been strip-mined. The phosphate deposits were virtually exhaust ...

Notes

{{Nauru topics Geography of Nauru