Umi Jigoku — Sea Hell

Umi Jigoku, que significa Mar del Infierno, es el mas fotografiado de los jigoku de Beppu. El extraordinario color azul cobalto de la piscina resulta del sulfato ferrico disuelto, que dispersa la luz de la misma manera que el agua del oceano. A pesar de alcanzar los 98°C, la piscina tiene un pH casi neutro.

Umi Jigoku, meaning Sea Hell, is the most photographed of Beppu's jigoku — a series of geothermal pools that have been tourist landmarks in Oita Prefecture since the early 20th century. The pool's remarkable cobalt blue colour results from dissolved ferric sulphate, which scatters light in the same way that ocean water does. Despite reaching 98°C, the pool has a near-neutral pH, making it compositionally different from the acidic springs found elsewhere in Japan. A volcanic eruption over 1,200 years ago created the underground hydrothermal system that still feeds the pool today.

Umi Jigoku — Sea Hellは日本・Oitaに位置する含鉄泉・塩化物泉。源泉温度は98℃の豊かな温泉水が湧き出る。泉水は中性に近い（pH約6.8）の泉質、塩化物泉・硫酸第二鉄を豊富に含む、総溶解固形物890 mg/Lが特徴だ。1200年頃に発見された。リラクゼーション・足のケアなど多様な温浴療法が行われる。施設では観賞・足湯・蒸気調理などが体験できる。