Pacific Ocean

Prehistory

Across the continents of Asia, Australia and the Americas, more than 25,000 islands, large and small, rise above the surface of the Pacific Ocean. Multiple islands are the shells of former active volcanoes that have lain dormant for thousands of years (see also Ring of Fire). Close to the equator, without vast areas of blue ocean, are a dot of atolls that have over intervals of time been formed by seamounts as a result of tiny coral islands strung in a ring within surroundings of a central lagoon.

Early migrations

Important human migrations occurred in the Pacific in prehistoric times. Modern humans first reached the western Pacific in the Paleolithic, at around 60,000 to 70,000 years ago. Originating from a southern coastal human migration out of Africa, they reached East Asia, Mainland Southeast Asia, the Philippines, New Guinea, and then Australia by making the sea crossing of at least 80 kilometres (50 mi) between Sundaland and Sahul. It is not known with any certainty what level of maritime technology was used by these groups – the presumption is that they used large bamboo rafts which may have been equipped with some sort of sail. The reduction in favourable winds for a crossing to Sahul after 80,000 B.P. fits with the dating of the settlement of Australia, with no later migrations in the prehistoric period. The seafaring abilities of pre-Austronesian residents of Island South-east Asia are confirmed by the settlement of Buka by 32,000 B.P. and Manus by 25,000 B.P. Journeys of 180 kilometres (110 mi) and 230 kilometres (140 mi) are involved, respectively.^[8]

The descendants of these migrations today are the Negritos, Melanesians, and Indigenous Australians. Their populations in maritime Southeast Asia, coastal New Guinea, and Island Melanesia later intermarried with the incoming Austronesian settlers from Taiwan and the northern Philippines, but also earlier groups associated with Austroasiatic-speakers, resulting in the modern peoples of Island Southeast Asia and Oceania.^[9][10]

A later seaborne migration is the Neolithic Austronesian expansion of the Austronesian peoples. Austronesians originated from the island of Taiwan c. 3000–1500 BCE. They are associated with distinctive maritime sailing technologies (notably outrigger boats, catamarans, lashed-lug boats, and the crab claw sail) – it is likely that the progressive development of these technologies were related to the later steps of settlement into Near and Remote Oceania. Starting at around 2200 BCE, Austronesians sailed southwards to settle the Philippines. They crossed the western Pacific from the Bismarck Archipelago to reach the Marianas Islands by 1500 BCE,^[11] as well as Palau and Yap by 1000 BCE. They were the first humans to reach Remote Oceania, and the first to cross vast distances of open water. They also continued spreading southwards and settling the rest of Maritime Southeast Asia, reaching Indonesia and Malaysia by 1500 BCE, and further west to Madagascar and the Comoros in the Indian Ocean by around 500 CE.^[12][13][14] More recently, it is suggested that Austronesians expanded already earlier, arriving in the Philippines already in 7000 BCE. Additional earlier migrations into Insular Southeast Asia, associated with Austroasiatic-speakers from Mainland Southeast Asia, are estimated to have taken place already in 15000 BCE.^[15]

At around 1300 to 1200 BCE, a branch of the Austronesian migrations known as the Lapita culture reached the Bismarck Archipelago, the Solomon Islands, Vanuatu, Fiji, and New Caledonia. From there, they settled Tonga and Samoa by 900 to 800 BCE. Some also back-migrated northwards in 200 BCE to settle the islands of eastern Micronesia (including the Carolines, the Marshall Islands, and Kiribati), mixing with earlier Austronesian migrations in the region. This remained the furthest extent of the Austronesian expansion into Polynesia until around 700 CE when there was another surge of island exploration. They reached the Cook Islands, Tahiti, and the Marquesas by 700 CE; Hawaiʻi by 900 CE; Rapa Nui by 1000 CE; and finally New Zealand by 1200 CE.^[13][16][17] Austronesians may have also reached as far as the Americas, although evidence for this remains inconclusive.^[18][19]

European exploration

The first contact of European navigators with the western edge of the Pacific Ocean was made by the Portuguese expeditions of António de Abreu and Francisco Serrão, via the Lesser Sunda Islands, to the Maluku Islands, in 1512,^[20][21] and with Jorge Álvares's expedition to southern China in 1513,^[22] both ordered by Afonso de Albuquerque from Malacca.

The eastern side of the ocean was encountered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and reached a new ocean.^[23] He named it Mar del Sur ("Sea of the South" or "South Sea") because the ocean was to the south of the coast of the isthmus where he first observed the Pacific.

In 1520, navigator Ferdinand Magellan and his crew were the first to cross the Pacific in recorded history. They were part of a Spanish expedition to the Spice Islands that would eventually result in the first world circumnavigation. Magellan called the ocean Pacífico (or "Pacific" meaning, "peaceful") because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century.^[24] Magellan stopped at one uninhabited Pacific island before stopping at Guam in March 1521.^[25] Magellan himself died in the Philippines in 1521. Spanish navigator Juan Sebastián Elcano led the remains of the expedition back to Spain across the Indian Ocean and round the Cape of Good Hope, completing the first world circumnavigation in 1522.^[26] Sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions encountered the Caroline Islands,^[27] the Aru Islands,^[28] and Papua New Guinea.^[29] In 1542–43 the Portuguese also reached Japan.^[30]

In 1564, five Spanish ships carrying 379 soldiers crossed the Pacific from Mexico led by Miguel López de Legazpi, and colonized the Philippines and Mariana Islands.^[31] For the remainder of the 16th century, Spain maintained military and mercantile control, with ships sailing from Mexico and Peru across the Pacific Ocean to the Philippines via Guam, and establishing the Spanish East Indies. The Manila galleons operated for two and a half centuries, linking Manila and Acapulco, in one of the longest trade routes in history. Spanish expeditions also arrived at Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, Vanuatu, the Marshalls and the Admiralty Islands in the South Pacific.^[32]

Later, in the quest for Terra Australis ("the [great] Southern Land"), Spanish explorations in the 17th century, such as the expedition led by the Portuguese navigator Pedro Fernandes de Queirós, arrived at the Pitcairn and Vanuatu archipelagos, and sailed the Torres Strait between Australia and New Guinea, named after navigator Luís Vaz de Torres. Dutch explorers, sailing around southern Africa, also engaged in exploration and trade; Willem Janszoon, made the first completely documented European landing in Australia (1606), in Cape York Peninsula,^[33] and Abel Janszoon Tasman circumnavigated and landed on parts of the Australian continental coast and arrived at Tasmania and New Zealand in 1642.^[34]

In the 16th and 17th centuries, Spain considered the Pacific Ocean a mare clausum – a sea closed to other naval powers. As the only known entrance from the Atlantic, the Strait of Magellan was at times patrolled by fleets sent to prevent the entrance of non-Spanish ships. On the western side of the Pacific Ocean the Dutch threatened the Spanish Philippines.^[35]

The 18th century marked the beginning of major exploration by Russians in Alaska and the Aleutian Islands, such as the First Kamchatka expedition and the Great Northern Expedition, led by the Danish-born Russian navy officer Vitus Bering. Spain also sent expeditions to the Pacific Northwest, reaching Vancouver Island in southern Canada, and Alaska. The French explored and colonized Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii, and the North American Pacific Northwest. In 1768, Pierre-Antoine Véron, a young astronomer accompanying Louis Antoine de Bougainville on his voyage of exploration, established the width of the Pacific with precision for the first time in history.^[36]

One of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific.^[32]

• 
  Made in 1529, the Diogo Ribeiro map was the first to show the Pacific at about its proper size
• 
  Map of the Pacific Ocean during European Exploration, circa 1754.
• 
  Maris Pacifici by Ortelius (1589). One of the first printed maps to show the Pacific Ocean^[37]
• 
  Map of the Pacific Ocean during European Exploration, circa 1702–1707

New Imperialism

Growing imperialism during the 19th century resulted in the occupation of much of Oceania by European powers, and later by Japan and the by United States. Significant contributions to oceanographic knowledge were made by the voyages of HMS Beagle in the 1830s, with Charles Darwin aboard;^[38] HMS Challenger during the 1870s;^[39] the USS Tuscarora (1873–76);^[40] and the German Gazelle (1874–76).^[41]

In Oceania, France obtained a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853, respectively.^[42] After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro negotiated the incorporation of the island into Chile with native Rapanui in 1888. By occupying Easter Island, Chile joined the imperial nations.^[43]: 53 By 1900 nearly all Pacific islands were in control of Britain, France, United States, Germany, Japan, and Chile.^[42]

In 1898 (Spanish–American War), the United States gained control of Guam and the Philippines from Spain.^[44]

20th century

This section needs expansion. You can help by adding missing information. (March 2026)

Prior to World War I United States attempted to purchase or at least establish a naval base in Galápagos Islands. Ecuador's staunch resistance to a US purchase or bases in the islands can be credited to Chilean diplomacy, which in turn was informally backed on this issue by Great Britain and Germany.^[45]

The end of World War I strengthened Japan and the United States in the Pacific, Japan in East Asia and United States mostly so in Latin America. Pacific rim countries like Colombia, Ecuador and Peru started to treat the United States as a hegemon, often seeking its mediation in international disputes.^[46] Chile on the other hand attempted to resist United States influence.^[47]

The Washington Naval Treaty of 1921 is associated with various geopolitical effects in the Pacific Ocean, including the end of the Anglo-Japanese Alliance. Although it was not part of the Washington Treaty in any way, the American delegates had made it clear that they would not agree to the treaty unless the British ended their alliance with the Japanese.^[48] The 1921 Imperial Conference earlier in the year had already decided not to renew the Alliance.^[49] The regrouping the Royal Navy in 1921 also meant that it left the South Pacific that year.^[50] This weakened the position of Britain's old-time ally Chile and increased the influence of the United States in the Americas. Indirectly, the withdrawal emboldened Peruvian and Bolivian claims against Chile as these two states were often supported diplomatically by the United States.^[50][51]

Japan occupied many Pacific islands during the Pacific War (1941–1945); however, by the end of that war, Japan was defeated and the U.S. Pacific Fleet was the virtual master of the ocean. The Japanese-ruled Northern Mariana Islands came under the control of the United States.^[52]

Since the end of World War II, many former colonies in the Pacific have become independent states (→ Decolonisation of Asia).

Bordering countries

(Inhabited dependent territories are denoted by the asterisk (*), with names of the corresponding sovereign states in round brackets. Associated states in the Realm of New Zealand are denoted by the hash sign (#).)

Uninhabited territories

Territories with no permanent civilian population.

Landmasses and islands

The Pacific Ocean has most of the islands in the world. There are about 25,000 islands in the Pacific Ocean.^[64][65][66] The islands entirely within the Pacific Ocean can be divided into three main groups known as Micronesia, Melanesia and Polynesia. Micronesia, which lies north of the equator and west of the International Date Line, includes the Mariana Islands in the northwest, the Caroline Islands in the center, the Marshall Islands to the east and the islands of Kiribati in the southeast.^[67][68]

Melanesia, to the southwest, includes New Guinea, the world's second largest island after Greenland and by far the largest of the Pacific islands. The other main Melanesian groups from north to south are the Bismarck Archipelago, the Solomon Islands, Santa Cruz, Vanuatu, Fiji and New Caledonia.^[69]

The largest area, Polynesia, stretching from Hawaii in the north to New Zealand in the south, also encompasses Tuvalu, Tokelau, Samoa, Tonga and the Kermadec Islands to the west, the Cook Islands, Society Islands and Austral Islands in the center, and the Marquesas Islands, Tuamotu, Mangareva Islands, and Easter Island to the east.^[70]

Islands in the Pacific Ocean are of four basic types: continental islands, high islands, coral reefs and uplifted coral platforms. Continental islands lie outside the andesite line and include New Guinea, the islands of New Zealand, and the Philippines. Some of these islands are structurally associated with nearby continents. High islands are of volcanic origin, and many contain active volcanoes. Among these are Bougainville, Hawaii, and the Solomon Islands.^[71]

The coral reefs of the South Pacific are low-lying structures that have built up on basaltic lava flows under the ocean's surface. One of the most dramatic is the Great Barrier Reef off northeastern Australia with chains of reef patches. A second island type formed of coral is the uplifted coral platform, which is usually slightly larger than the low coral islands. Examples include Banaba (formerly Ocean Island) and Makatea in the Tuamotu group of French Polynesia.^[72][73]

• 
  Ladrilleros Beach in Colombia on the coast of Chocó natural region
• 
  Tahuna maru islet, French Polynesia
• 
  Los Molinos on the coast of Southern Chile

Geological history

The Pacific Ocean was born 750 million years ago at the breakup of Rodinia, although it is generally called the Panthalassa until the breakup of Pangea, about 200 million years ago.^[94] The oldest Pacific Ocean floor is only around 180 Ma old, with older crust subducted by now.^[95]

Seamount chains

The Pacific Ocean contains several long seamount chains, formed by hotspot volcanism. These include the Hawaiian–Emperor seamount chain and the Louisville Ridge.

Fishing

Fish are an important economic asset in the Pacific. The shallower shoreline waters of the continents and the more temperate islands yield herring, salmon, sardines, snapper, swordfish, and tuna, as well as shellfish.^[97] Overfishing has become a serious problem in some areas. Overfishing leads to depleted fish populations and closed fisheries, causing both economic and ecologic consequences.^[98] For example, catches in the rich fishing grounds of the Okhotsk Sea off the Russian coast have been reduced by at least half since the 1990s as a result of overfishing.^[99]

Nuclear waste

From 1946 to 1958, Marshall Islands served as the Pacific Proving Grounds, designated by the United States, and played host to a total of 67 nuclear tests conducted across various atolls.^[108][109] Several nuclear weapons were lost in the Pacific Ocean,^[110] including one-megaton bomb that was lost during the 1965 Philippine Sea A-4 incident.^[111]

In 2021, the discharge of radioactive water from the Fukushima nuclear plant into the Pacific Ocean over a course of 30 years was approved by the Japanese Cabinet. The Cabinet concluded the radioactive water would have been diluted to drinkable standard.^[112] Apart from dumping, leakage of tritium into the Pacific was estimated to be between 20 and 40 trillion Bqs from 2011 to 2013, according to the Fukushima plant.^[113]

Deep sea mining

An emerging threat for the Pacific Ocean is the development of deep-sea mining. Deep-sea mining is aimed at extracting manganese nodules that contain minerals such as magnesium, nickel, copper, zinc and cobalt. The largest deposits of these are found in the Pacific Ocean between Mexico and Hawaii in the Clarion Clipperton fracture zone.

Deep-sea mining for manganese nodules appears to have drastic consequences for the ocean. It disrupts deep-sea ecosystems and may cause irreversible damage to fragile marine habitats.^[114] Sediment stirring and chemical pollution threaten various marine animals. In addition, the mining process can lead to greenhouse gas emissions and promote further climate change. Preventing deep-sea mining is therefore important to ensure the long-term health of the ocean.^[115]

List of major ports