Coral island in the context of "Niue"

The Ryukyu Islands (Japanese: 琉球列島, Hepburn: Ryūkyū Rettō), also known as the Nansei Islands (南西諸島, Nansei Shotō; lit. 'Southwest Islands') or the Ryukyu Arc (琉球弧, Ryūkyū-ko), are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ryukyu Islands are divided into the Satsunan Islands (Ōsumi, Tokara and Amami) and Okinawa Prefecture (Daitō, Miyako, Yaeyama, Senkaku, Okinawa, Sakishima Islands (further divided into the Miyako and Yaeyama Islands), and Yonaguni as the westernmost). The larger ones are mostly volcanic islands and the smaller mostly coral. The largest is Okinawa Island.

The climate of the islands ranges from humid subtropical climate (Köppen climate classification Cfa) in the north to tropical rainforest climate (Köppen climate classification Af) in the south. Precipitation is very high and is affected by the rainy season and typhoons. Except the outlying Daitō Islands, the island chain has two major geologic boundaries, the Tokara Strait (between the Tokara and Amami Islands) and the Kerama Gap (between the Okinawa and Miyako Islands). The islands beyond the Tokara Strait are characterized by their coral reefs.

An atoll (/ˈæt.ɒl, -ɔːl, -oʊl, əˈtɒl, -ˈtɔːl, -ˈtoʊl/) is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical parts of the oceans and seas where corals can develop. Most of the approximately 440 atolls in the world are in the Pacific Ocean.

Two different, well-cited models, the subsidence model and the antecedent karst model, have been used to explain the development of atolls. According to Charles Darwin's subsidence model, the formation of an atoll is explained by the sinking of a volcanic island around which a coral fringing reef has formed. Over geologic time, the volcanic island becomes extinct and eroded as it subsides completely beneath the surface of the ocean. As the volcanic island subsides, the coral fringing reef becomes a barrier reef that is detached from the island. Eventually, the reef and the small coral islets on top of it are all that is left of the original island, and a lagoon has taken the place of the former volcano. The lagoon is not the former volcanic crater. For the atoll to persist, the coral reef must be maintained at the sea surface, with coral growth matching any relative change in sea level (sinking of the island or rising oceans).

Geologically, a volcanic island is an island of volcanic origin. The term high island can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed on sunken volcanoes).

Pratas Island, also known as the Tungsha Islands or the Dongsha Islands (Chinese: 東沙群島; pinyin: Dōngshā Qúndǎo; Pe̍h-ōe-jī: Tang-soa Kûn-tó; lit. 'East Sand Islands'), is a coral island situated in the northern part of the South China Sea administered as part of Cijin District, Kaohsiung, Taiwan. It is located about 170 nautical miles (310 km; 200 mi) southeast of Hong Kong. It has an area of about 240 hectares (590 acres), including 64 hectares (160 acres) of lagoon, and is the largest of the South China Sea Islands. It is the location of the Dongsha Airport.

There are three undersea features in the waters associated with Pratas Island: Pratas Atoll, North Vereker Bank and South Vereker Bank. The atoll is circular, and the crescent-shaped Pratas Island occupies its western part. Below the ocean's surface to the northwest (21°N 116°E / 21°N 116°E / 21; 116) of Pratas Island, North Vereker Bank rises to 11 metres (36 ft) below sea level and South Vereker Bank to 58 metres (190 ft) below sea level.

The Florida Keys are a coral cay archipelago off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about 15 miles (24 km) south of Miami and extend in an arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry Tortugas. The islands lie along the Florida Straits, dividing the Atlantic Ocean to the east from the Gulf of Mexico to the northwest, and defining one edge of Florida Bay. The southern part of Key West is 93 miles (150 km) from Cuba. The Keys are located between about 24.3 and 25.5 degrees north latitude.

More than 95% of the land area lies in Monroe County, but a small portion extends northeast into Miami-Dade County, such as Totten Key. The total land area is 137.3 square miles (356 km). At the 2010 census the population was 73,090, with an average density of 532.34 per square mile (205.54/km), although much of the population is concentrated in a few areas of much higher density, such as the city of Key West, which has 32% of the Keys' total population. The 2014 Census population estimate was 77,136. The 2020 Census population estimate was 82,874.

The Cocos (Keeling) Islands (Cocos Islands Malay: Pulu Kokos [Keeling]), officially the Territory of Cocos (Keeling) Islands (/ˈkoʊkəs/; Cocos Islands Malay: Pulu Kokos [Keeling]), are an Australian external territory in the Indian Ocean, comprising a small archipelago approximately midway between Australia and Sri Lanka and relatively close to the Indonesian island of Sumatra. The territory's dual name (official since the islands' incorporation into Australia in 1955) reflects that the islands have historically been known as either the Cocos Islands or the Keeling Islands.

The territory consists of two atolls made up of 27 coral islands, of which only two – West Island and Home Island – are inhabited. The population of around 600 people consists mainly of Cocos Malays, who mostly practise Sunni Islam and speak a dialect of Malay as their first language. The territory is administered by the Australian federal government's Department of Infrastructure, Transport, Regional Development, Communications and the Arts as an Australian external territory and together with Christmas Island (which is about 960 kilometres (600 mi) to the east) forms the Australian Indian Ocean Territories administrative grouping. However, the islanders do have a degree of self-government through the local shire council. Many public services – including health, education, and policing – are provided by the state of Western Australia, and Western Australian law applies except where the federal government has determined otherwise. The territory also uses Western Australian postcodes.

Howland Island (/ˈhaʊlənd/) is a coral island and strict nature reserve located just north of the equator in the central Pacific Ocean, about 1,700 nautical miles (3,100 km) southwest of Honolulu. The island lies almost halfway between Hawaii and Australia and is an unincorporated, unorganized territory of the United States. Together with Baker Island, it forms part of the Phoenix Islands. For statistical purposes, Howland is grouped as one of the United States Minor Outlying Islands. The island has an elongated cucumber-shape on a north–south axis, 1.40 by 0.55 miles (2.25 km × 0.89 km), and covers 1 square mile (640 acres; 2.6 km).

Howland Island National Wildlife Refuge consists of the entire island and the surrounding 32,074 acres (129.80 km) of submerged land. The island is managed by the U.S. Fish and Wildlife Service as an insular area under the U.S. Department of the Interior. It is part of the Pacific Islands Heritage Marine National Monument.

Jarvis Island (/ˈdʒɑːrvɪs/; formerly known as Bunker Island or Bunker's Shoal) is an uninhabited 4.5 km (1.7 sq mi) coral island located in the South Pacific Ocean, about halfway between Hawaii and the Cook Islands. It is an unincorporated, unorganized territory of the United States, administered by the United States Fish and Wildlife Service of the United States Department of the Interior as part of the National Wildlife Refuge system. Unlike most coral atolls, the lagoon on Jarvis is wholly dry.

Jarvis is one of the Line Islands and, for statistical purposes, is also grouped as one of the United States Minor Outlying Islands. Jarvis Island is the largest of three U.S. equatorial possessions, which include Baker Island and Howland Island.