This chapter discusses the origins of islands by appearance and composition, beginning with nascent ocean-floor islands – from which all oceanic islands develop – through mature above-sea oceanic islands and older sunken islands. All oceanic islands form as a result of volcanic activity on the deep ocean floor. Islands made from newly-erupted volcaniclastic material may disappear through wave erosion once the eruption ends. Like other landscapes, island landscapes vary in character primarily because of geology and climate. The nature of landscapes of active volcanoes varies, depending on that of the eruptive materials. The island environments that people see today manifest the subtle interplay of nature and humans and it is consequently difficult to generalise about their long-term evolution. The four critical controls on long-term environmental evolution of most islands are geology, climate, and extreme or rapid events. The key element in understanding the evolution of island environments is time, specifically how much has elapsed since that island appeared.