[2] The island is a stratovolcano with a granitic composite cone, dating from the late Pleistocene period, between 10,000 and 2,000 years ago.

The highest elevation Mount Oyama (雄山, Oyama-san) is an active volcano with a height of 759 meters.

[3] On July 14, 2000, Mount Oyama began another series of eruptions, and by September, the island was completely evacuated.

Miyake-jima is home to an unusually rich flora and fauna with several rare species of birds and animals, although its natural habitats are constantly under threat from human and volcanic activity.

Underwater, the island is valued by divers for its coral reefs and marine fauna (including the dolphin population outside nearby Mikura-jima).

Miyake Village (三宅村, Miyake-mura) serves as the local government of the island, and also includes nearby tiny uninhabited Ōnoharajima west south-west of Miyake-jima.

The island is accessible by an over-night ferry called the Tachibana Maru (橘丸), which is operated by Tōkai Kisen.

A second large passenger ship named Salvia Maru (さるびあ丸) also started servicing Miyake-jima on June 25, 2020.

The area is prone to high volume of sulfuric gas and flights were suspended for almost eight years after the July 14, 2000 volcano eruption.