Oceanic islands are landforms that rise from the ocean floor, typically formed by volcanic activity or coral reef development. They are surrounded by water and can vary in size, from small islets to large landmasses. These islands are often characterized by unique ecosystems and biodiversity, as they can host species that are not found anywhere else in the world. There are two main types of oceanic islands: volcanic islands, which are created by eruptions from underwater volcanoes, and coral islands, formed from the accumulation of coral debris. Examples of oceanic islands include the Hawaiian Islands and the Galápagos Islands, both known for their distinct wildlife and geological features.