Island

Island describes land entirely encircled by water. Islands vary in size from small cays only a few meters wide to large landmasses such as greenland or Australia. They form through volcanic eruptions, coral reef growth, tectonic uplift, or sea-level rise that floods lowlands around existing hills.

Volcanic islands, like Hawaii, rise when magma from hot spots reaches the surface and cools. Over time, erosion carves cliffs, beaches, and valleys. coral islands and atolls grow as reefs accumulate limestone skeletons; if a volcano sinks, the reef may remain as a ring around a central lagoon. Continental islands, such as Great Britain, separated from mainland areas when glacial melt raised sea levels.

Islands host unique ecosystems because water barriers limit which species arrive. Many evolve into endemic species found nowhere else—think of Madagascar's lemurs or the Galápagos finches. Isolation also makes island wildlife vulnerable to invasive predators, diseases, and habitat loss.

Humans value islands for culture, tourism, and strategic location. Ports on islands handle shipping lanes, while resorts draw visitors to beaches and reefs. However, limited land and freshwater make sustainable development challenging. Islanders often depend on imported goods and must carefully manage waste and energy.

Rising sea levels and stronger storms threaten low-lying islands. Some governments build sea walls, restore mangroves, or relocate communities to higher ground. Studying island geology and ecology helps scientists understand plate tectonics, evolution, and the impacts of climate change.