4. An island volcano, the residents of Miyake-Jima are forced to carry gas masks at all times due to the risk of toxic levels of sulfur dioxide in the surrounding air
An island in the Izu archipelago, situated approximately 180 kilometers southeast of Honshu, Japan, in the Philippine Sea, Miyake-Jima comprises an inhabited volcano: Mount Oyama. Formed during the late Pleistocene period, between ten to fifteen thousand years ago, Miyake-Jima, with a 38.3-kilometer coastline, is home to a variety of rich fauna that endures the constant threat of eruption. In fact, so does the local population, estimated to be 2,451 as of mid-2016. The volcano in the center of the small island has erupted at least 13 times in the last 500 years, including five times since the start of the Meiji period in 1868, and in 1940 was responsible for the deaths of at least 11 people.
These eruptions by Mount Oyama have inflicted lasting consequences for the island and its inhabitants. Following the start of a series of eruptions on July 14, 2000, the island was swiftly evacuated, with residents unable to return until February 1, 2005. However, during this four-year absence and sporadic activity, Mount Oyama had imparted a constant discharge of sulfur dioxide gas into the surrounding environment. Although not permanently inducing levels of dangerous toxicity, all residents of Miyake-Jima are now required to carry gas masks at all times, with alarms ready to alert inhabitants should the toxic gas reach critical levels.