A low island is, in geology (and sometimes in archaeology), an island of coral origin. The term applies whether the island was formed as a result of sedimentation upon a coral reef or of the uplifting of such islands. The term is used to distinguish such islands from high islands, whose origins are volcanic.
This distinction is important to understand, as there are some low islands, such as Makatea, Nauru, Niue and Banaba, which rise several hundred feet above sea level, while a number of high islands rise no more than a few feet above sea level, often classified as "rocks".
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 high islands.
Low islands have poor, sandy soil and little fresh water, which makes them difficult to farm. They don't support human inhabitation as well as high islands. The people that do live on low islands survive by mostly fishing.