The island itself, which consists of volcanic rocks (mainly Anzangan rock (andesite)), is mostly surrounded by a vertical cliff and is covered by a virgin forest of evergreen broad-leaved trees such as Machilus thunbergii.
島自体は、安山岩を主に火山性の岩石で、周囲のほとんどが切り立った崖になっており、タブノキなどの常緑広葉樹の原生林で覆われている。