What are the geographical features of Oceania?

Oceania is characterized by a diverse range of geographical features, including numerous islands, archipelagos, and atolls scattered across the Pacific Ocean. The region comprises four main subregions: Melanesia, Micronesia, Polynesia, and Australasia. Notable features include the Great Barrier Reef off the coast of Australia, volcanic islands like those in Hawaii, and the rugged mountains of New Zealand. Additionally, Oceania encompasses vast oceanic expanses and a variety of ecosystems, from tropical rainforests to arid deserts.