Aogashima is a volcano inside a volcano, 360 kilometres south of Tokyo and still part of the city. The outer crater is a kilometre and a half across, and the 223-metre cone of Maruyama stands on its floor. About 160 people live up on the outer rim, farm the crater floor and cook on its steam vents. The climb to Otonbu, the 423-metre high point of the rim, is where the island finally explains itself to you. The green bowl is complete from up there, the cone rising out of the middle of it, and open ocean runs in every direction, with Hachijojima on the horizon on a clear day.
There is no bay here and no breakwater. Cargo swings ashore at a short pier under the cliff, and a crane plucks the fishing boats out of the sea onto a concrete shelf. The coast is a wall of dark rock hundreds of metres high, and the ferry from Hachijojima sails about half the days it is scheduled. Everyone lives in two hamlets on the rim, Yasundogo and Nishigo — a school, a couple of small shops, and roads that switchback down the slope. The whole settlement takes you minutes to cross. On the crater floor, at the Hingya vents, the islanders have set cooking pots straight over the steam for anyone to use. You put in eggs or sweet potatoes, open the tap, and twenty minutes does it. The same heat runs a mist sauna next door and a saltworks that burns nothing, warming seawater so gently that the crystals take weeks. After dark nothing is lit, and the stars come down to the crater walls all the way round you. The island has been empty once. The eruption of 1785 killed a third of the people and drove the rest to Hachijojima, and the first attempts to return failed. The headman pushed the crossings through one boat at a time, and by 1835 the community was whole again on the volcano that had nearly finished it. They have a word for what they did: kanju, to live here again.