Oceanic islands in the context of "Atoll"

Mainland is defined as "relating to or forming the main part of a country or continent, not including the islands around it [regardless of status under territorial jurisdiction by an entity]." The term is often politically, economically and/or demographically more significant than politically associated remote territories, such as exclaves or oceanic islands situated outside the continental shelf.

In geography, "mainland" can denote the continental part of any polity or the main island within an island nation. In geopolitics, "mainland" is sometimes used interchangeably with terms like metropole as an antonym to overseas territories. In the sense of "heartland", mainland is the opposite of periphery. In some language a separate concept of "mainland" is missing and is replaced with a "continental portion".

This is a list of islands in the Atlantic Ocean, the largest of which is Greenland. Note that the definition of the ocean used by the International Hydrographic Organization (IHO) excludes the seas, gulfs, bays, etc., bordering the ocean itself. Thus, for instance, not all of the islands of the United Kingdom are actually in or bordering on the Atlantic. For reference, islands in gulfs and seas are included in a separate section. Oceanic islands are formed by seamounts rising from the ocean floor with peaks above the surface of the ocean and are not parts of continental tectonic plates.

Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt is characterized by relatively high alkali (Na₂O and K₂O) content relative to other basalts and by the presence of olivine and titanium-rich augite in its groundmass and phenocrysts, and nepheline in its CIPW norm.