What Is Izu Oshima, and How Do You See Mt. Mihara and Ura-Sabaku?
This guide is for visitors who want to know what makes Izu Oshima worth the boat trip, and how to walk up Mt. Mihara and across the black "desert" safely. It explains the volcano, the main sights and the safety advice the geopark gives to walkers.
We used the Oshima Tourism Association, the Izu Oshima Geopark site, the Tokyo Metropolitan Government's tourism pages and the island information site Oshima Navi. All pages were read on 2026-10-04. Times and fees can change, so check on the day. We name no hotels or restaurants and left out phone numbers.
What Izu Oshima is
The tourism association says Izu Oshima is the largest island in the Izu Islands, floating about 120 km south of central Tokyo. In its centre stands Mt. Mihara, 758 metres high, which is still volcanically active. The island is in Fuji-Hakone-Izu National Park, and about 97 percent of it is regulated under the Natural Parks Act, so the landscape and ecosystem are well protected. It is certified as a Japan Geopark.
The association says people are said to have lived here for about 8,000 years. Islanders feared and revered Mt. Mihara's repeated eruptions as "Gojinka", the sacred fire. Until the middle of the Edo period it was a place of exile, mainly for political prisoners, and the warrior Minamoto no Tametomo was sent here after losing in the Hogen Rebellion.
Mt. Mihara and the crater
The Tokyo government's course page says Mt. Mihara is a central cone inside the summit caldera, created by the An'ei eruption of 1777. It has a steep, shaft-like crater 300 metres wide and more than 200 metres deep. The page says it has been quiet since the 1986 eruption and that from the top you can see the Izu Islands, the Izu Peninsula and Mt. Fuji. Oshima Navi gives the crater as about 300 to 350 metres wide and about 200 metres deep.
The geopark's summit-area course page suggests two walks:
- Crater rim course: about 2 hours 45 minutes, or 3 hours 30 minutes to 4 hours with a guide. It starts at the Mihara-yama Summit Entrance car park and passes the tip of the 1986 lava flow and the central crater.
- Mt. Mihara and Ura-Sabaku full course: about 3 hours 30 minutes, or 5 to 6 hours with a guide, from the summit entrance to the car park of a hot spring hotel. The start and finish are different places, and route buses serve both.
Oshima Navi's guided trek, on a similar route, quotes the signboard figure of 7.9 km and 155 minutes. At the summit entrance, a geopark exhibition is open on weekends and public holidays, according to the geopark page.
Ura-Sabaku, the black desert
The tourism association says Ura-Sabaku is the only place in Japan marked as a desert on the map. Its barren black ground is said to look like the moon. It is reached by bus from Motomachi Port in about 36 minutes to the stop called Mihara-yama Sancho-guchi.
Other sights the sources point to
- Striped strata: the association describes a striped layer more than 600 metres long beside the ring road, made of about 100 eruptions over the past 20,000 years. The Tokyo government says it stands about 30 metres tall and is nicknamed after a layered cake, while Oshima Navi says about 24 metres high and 630 metres long. We could not tell which figure is more accurate, so treat them as approximate.
- Fude-jima: a hard rock left in the sea from an ancient volcanic vent, once revered as a place where a god lives.
- Habu Port: in the south, a former crater lake that a large tsunami linked to the sea. It was later widened into a port.
- The Oshima cherry tree: the oldest and largest on the island, over 800 years old and a special natural monument since 1952.
- Volcano Museum: it records the 1986 eruption and explains volcano science. The association's page gave 9:00 to 17:00 and 500 yen for adults, but check before you go.
- Camellia garden at Oshima Park: 7 hectares, about 1,000 varieties and 3,200 garden plants plus 5,000 wild camellias, about 35 minutes by bus from Motomachi Port.
Safety on the volcano
This is the most important part. The geopark's volcano page, last updated in March 2026, says the current eruption alert level is 1, "active volcano, be aware". It says there are no signs of an eruption now, but warns that sudden ash eruptions are possible and that magma has built up deep underground. It asks walkers on Mt. Mihara to do the following:
- Check the current volcano information first. The page links to the Japan Meteorological Agency's pages and live cameras.
- Wear hiking shoes, because the promenade has rough footing. A helmet is advised, and the summit entrance rest house lends helmets free of charge.
- Know what to do in a sudden eruption. Fist-sized rocks can fly more than a kilometre from the crater. Shelter in an evacuation shelter on the path, or behind rocks on the opposite side of the crater, and protect your head.
- Cover your mouth with a wet towel or mask against volcanic ash and gas, and do not enter hollows where gas gathers.
What we could not verify, and therefore left out
- Today's alert level, which the Japan Meteorological Agency publishes.
- Bus timetables to the summit entrance.
- The condition of the paths after this autumn's storms.
Related guides
- How to get to Izu Oshima by jet ferry, large ship and plane
- How do you get around Izu Oshima by bus, bike and car?
Sources
All URLs retrieved 2026-10-04.
- About Izu Oshima (Oshima Tourism Association, in Japanese) — (island, history, facilities)
- Play (Oshima Tourism Association, in Japanese) — (Ura-Sabaku, strata, Fude-jima)
- Information on Izu Oshima volcano (Izu Oshima Geopark, in Japanese) — (alert level, safety advice)
- Recommended model courses, summit area (Izu Oshima Geopark, in Japanese) — (courses)
- Izu Oshima special course (Tokyo Metropolitan Government) — (Mt. Mihara, strata, Habu Port)
- Mt. Mihara trekking (Oshima Navi, in Japanese) — (route figures)