The Izu Islands occupy the northern portion of the Izu-Bonin-Mariana Arc, the same tectonic structure that extends south to Mount Fuji and the Izu Peninsula on the Honshu mainland, ending at a tectonic triple junction. Volcanic activity is not occasional here -- it is the defining fact of existence. In 1952, the research vessel Kaiyo Maru No. 5 was destroyed by a submarine eruption at Myojin-sho, killing 31 people. The islands sit within the Fuji-Hakone-Izu National Park, but the designation does not diminish their volatility. Tokyo's metropolitan government has developed extensive disaster preparedness systems including hazard maps, evacuation guidance, radio networks, and emergency supply transport. The four southernmost uninhabited islands -- Bayonnaise Rocks, Smith Island, Torishima, and the dramatic sea stack called Sofu-iwa (Lot's Wife) -- remain unincorporated, claimed by both Hachijo Town and Aogashima Village, administered by neither.

The practice dates to the 12th century, possibly earlier. During the Edo period, the Tokugawa Shogunate formalized the system, designating Nii-jima, Miyake-jima, and Hachijo-jima as places of criminal exile. Convicts were shipped south from the mainland and left on these remote volcanic islands with little hope of return. The practice gave the archipelago a dark reputation that persisted long after the Meiji government ended it. Today the legacy survives in physical traces: exile cemeteries, execution grounds, and museum exhibits on Nii-jima document the lives of the 118 convicts banished there. But the islands' isolation produced another, more surprising inheritance. On Hachijo-jima, the centuries of separation fostered the Hachijo language -- a divergent tongue so different from standard Japanese that mainland speakers cannot understand it. Linguists classify it separately, a living artifact of the islands' long isolation.

The Izu Islands formed relatively recently in geological terms -- within the past few million years -- as oceanic islands with no land bridge to the mainland. Unlike truly remote archipelagos such as Hawaii or the Galapagos, the Izu chain sits close enough to Honshu that species have repeatedly colonized it by overseas dispersal. This combination of proximity and isolation has made the islands a natural laboratory for studying ecological and evolutionary processes. Campanula bellflowers colonized the entire archipelago in a single dispersal event. Euhadra snails, endemic to Japan, arrived the same way -- all individuals on the inhabited islands share an identical haplotype. The Apodemus field mice took a different path, colonizing from the mainland in two separate, independent events. Each species tells a different story about how life crosses open water and establishes itself on volcanic ground.

Getting to the Izu Islands from Tokyo takes 30 minutes by air, about two hours by jetfoil hydrofoil, or seven to ten hours by conventional ferry. Five airports serve the chain, supplemented by 15 harbors and 19 fishing ports. Helicopter connections reach islands too small for runways. The infrastructure reflects a practical reality: the Tokyo metropolitan government considers reliable transportation essential to maintaining quality of life on islands that had no electricity before 1953. By 1962, 98 percent of the area had power. The primary industries are fisheries, agriculture, and tourism, with summer crowds filling the most scenic spots. Visitors come for swimming, scuba diving, surfing, fishing, bird watching, and trekking. The largest island, Izu Oshima, is the traditional gateway. In 1643, the Dutch explorer Maarten Gerritsz Vries arrived and named the whole group the De Vries Archipelago. The name did not stick, but the archipelago's appeal to outsiders has never faded.

The administrative structure of the Izu Islands reflects Japan's broader approach to remote territory. Three subprefectures -- Oshima, Miyake, and Hachijo -- organize the islands as branch offices of the Tokyo Metropolitan Government. Two towns (Oshima and Hachijojima) and six villages account for the inhabited islands. But the uninhabited southern reaches defy neat categorization. Torishima, once inhabited, now serves as an important bird refuge. The deserted islands between Aogashima and the subtropical Ogasawara chain to the south exist in administrative limbo, controlled directly by Hachijo Subprefecture because no municipality has settled competing claims. Further south still, the Ogasawara Islands -- also part of Tokyo -- extend the metropolis more than a thousand kilometers from Shinjuku. The Izu Islands are where that improbable reach begins, the first volcanic stepping stones on Tokyo's long chain into the Pacific.