Volcanic island
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 volcanos). Definition and origin
There are a number of volcanic islands that rise no more than  above sea level, often classified as "islets or rocks", while some low islands, such as Banaba, Henderson Island, Makatea, Nauru, and Niue, as uplifted coral islands, rise over  above sea level. The two types of islands are often found in proximity to each other, especially among the islands of the South Pacific Ocean, where low islands are found on the fringing reefs that surround most volcanic islands. Volcanic islands normally arise above a hotspot. Habitability
Volcanic islands above a certain size usually have fresh groundwater, while low islands often do not, so volcanic islands are more likely to be habitable. See also

References

External links 
 Micronesian culture: High island and low island cultures at Britannica.com. Retrieved 2011-09-22. Islands by type