Mount Omuro (大室山 Ōmuroyama) is a volcano south of Ito City on the eastern coast of the Izu Peninsula. Extinct for 3,700 years, the cone-shaped mountain is completely covered in grass and has a circular trail around its crater mound at an altitude of 580 meters. The trail is about one kilometre in length. The Ōmuroyama Volcano Geosite is part of the Fuji-Hakone-Izu National Park (富士箱根伊豆国立公園 Fuji-Hakone-Izu Kokuritsu Kōen) that spans Yamanashi, Shizuoka, Kanagawa and parts of Tokyo.
The summit of Mount Ōmuro can only be accessed by chairlift (about 5 minutes) and offers spectacular panoramic views of Izu and the Izu Islands. Along the trail, there are stone images of jizō (地蔵), guardians of children and patron deities of deceased infants in Japanese culture. A small Shinto shrine sits on the bank of the crater which measures 300 meters in diameter. At the bottom of the crater is an archery range where visitors can practice their skills with bow and arrow. Visitors with valid pilot licenses can para-glide from the trail.
Every year on the second Sunday of February, the dead grass on the slopes of the mountain is burned in a ceremony called yamayaki (山焼き, literally "mountain burning"). Visitors can participate in the 700-year old tradition.
Visitors can use the archery range right in the crater.
Jizō statues along the crater trail
View onto the southern part of the volcano field (Mount Yahazuyama and Ananoyama, twin lava-domes created by high-viscosity lava)
The crater with Ito Onsen visible in the background
The chairlift to the crater
Lake Ippekiko (一碧湖), 2.5 kilometres north of Mount Ōmuro, is a crater lake of about 600 meters in diameter and a result of an explosive eruption 100,000 years ago. About 4,000 years ago large amounts of lava from Ōmuroyama flowed into the lake forming the Junirento ("Twelve Islands"). The red torii gate pays tribute to the legend of the Red Bull, a monster that lived in the lake and attacked boats crossing over its head. One day a compassionate priest banned the bull in exchange for his life.
Geological history of Izu and Mount Ōmuro
The Izu Tobu Volcanic Field is an active terrestrial and submarine monogenetic* volcanic field located on and off the Izu coastline. It has a long history of eruptions from Mount Tōgasa (遠笠山) which erupted 150,000 years ago to the latest outbreak in 1989, a phreatic** eruption between the city of Ito and Hatsushima island. Mount Ōmuro is another representative of the Izu Tobu Group and was formed by low-viscosity ejecta about 4,000 years ago. Large amounts of lava shaped the gentle Izu-Kōgen (Izu Highland) and the Jōgasaki Coast (城ヶ崎海岸 Jōgasaki kaigan).
The Izu Peninsula is the only part of Honshū located on the Philippine Sea Plate. Initially, it consisted of a group of volcanic islands and submarine volcanoes in the South China Sea. These islands and volcanos drifted by the northward motion of the Philippine Sea Plate and eventually collided with Honshū, the main island of Japan, about 600,000 years ago, thereby forming a peninsula. Even now, volcanic and crustal activities under Izu continue, resulting in an abundance of volcanic hot springs.
* Monogenetic volcanoes erupt only once, while polygenetic volcanoes repeatedly erupt over a period (like Mount Fuji).
** Phreatic eruptions, also known as steam-blast eruptions, occur when magma heats ground or surface water, causing near-instantaneous evaporation to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs.
Admission and access:
Address: 1317-5 Sakibara Futo, Ito City, Shizuoka 〒413-0231; phone: 0557-51-0258
Admission: chairlift 500 JPY per person (return ticket); dogs allowed (max shoulder height 45cm, max weight of 15 kilograms), chairlift hours: daily from 9:00-17:15; paragliding: day pass 1,000 JPY, annual pass: 10,000 JPY; archery: 600 JPY (adults), 400 JPY for children (4 year-old to elementary school), 400 JPY for lease of equipment.
- by train from Itō Station (JR East and Izu Kyūkō Line), take a bus from there to "Shaboten Koen" (シャボテン公園, Cactus Park), 40 minutes, departs every 30 minutes, 710 JPY, or from Izu Kogen Station, 20 minutes, leaves every 30 minutes, 360 JPY
- by bus with 1-day passes from Tokai Bus (either 800 JPY to Izu Kogen Station or 1,300 JPY including Central Itō and the Jōgasaki Coast)
- by car: from Itō follow Route 135 southbound, turn right towards Ōmuro at the Gran-Pal traffic signal.