
[Mount Chokai-Tobishima Geopark: Yuza and Sakata] The Shonai Plain is blessed with the bounty of Mount Chokai
table of contents
- 1 Mount Chokai was formed into its current shape by a major eruption during the Edo period
- 2 The Shonai Plain Eastern Edge Fault Zone stretches in a straight line for 35 km
- 3 The abundant waters of Mt. Chokai that nourish the Shonai Plain
- 4 "Miko no Mizu" - a blessing from the sacred mountain that is essential to life
- 5 Ushiwatari River and Maruike Pond, formed by spring water
- 6 Chokaisan Omonokimi Shrine, which enshrines the sacred mountain of Mt. Chokai
- 7 Sixteen Rakan Rocks carved into lava as a memorial for those who died in a maritime accident
- 8 Articles related to Mt. Chokai and Tobishima Geopark
Mount Chokaiis a rare mountain with two peaks (East Chokaisan Shinzan and West Chokaisan Nabemori) that extend straight from sea level (0m) on the Sea of Japan to its summit at 2,236m. Due to its beautiful appearance, it"Dewa Fuji."is called
It is an active volcano, and the people living at its foot, such as Yuza, Sakata, Kisakata (Nikaho City, Akita Prefecture), and Yuri (Yurihonjo City, Akita Prefecture), fear Mount Chokai, which sometimes spews fire as if in anger and shakes the earth, but they also worship it as a mountain where gods dwell, and as a source of abundant water
Mount Chokai was formed into its current shape by a major eruption during the Edo period
Mount Chokaibegan its activity about 550,000 years ago, and it is believed that lava covered the surface of West Mount Chokai (Nabemori Lava Dome/elevation 1,652m) around 160,000 to 20,000 years ago.
From about 20,000 years ago onwards, Mt. Higashi-Chokai, located in the eastern part of the mountain, was formed. About 2,600 years ago, the summit of Mt. Higashi-Chokai collapsed, and the resulting lava formed a crater floor (caldera), and the resulting deposits created the topography of the foothills
Of the two central cones of Mount Higashi-Chokai, Mount Shinzan (2,236m) is a lava dome formed in an eruption in 1801 (the first year of the Kyowa era), and is also known as Mount Kyowa
Mount Chokai erupted frequently until the late Heian period (900s). After that, there were no records of eruptions until the mid-1600s, but activity began to resume around 1659. Then, in 1801, a major eruption occurred that remains in historical records

Traces of the great eruption remain on the mountain and in the Shonai Plain
Phreatic eruptions that began in 1800 gradually became more intense, and in late August 1801 a major explosion occurred, killing eight climbers. In 1804 (the first year of the Bunka era), a major earthquake (Kisakata earthquake) occurred, causing extensive damage to the foothills of the mountain
There have been no large-scale eruptions since then. The most recent eruption was a small phreatic eruption near Shinzan in 1974 (Showa 49), which resulted in mudflows and ash fall. A swarm of earthquakes also occurred in 1987 (Showa 62)
The active volcano Mount Chokai has repeatedly altered the landscape with each eruption and earthquake, threatening people along the way. Traces of these events remain today in the unique topography of the Shonai region, including faults and lava flows. This distinctive landscape"Chokai-Tobishima Geopark,"has been designated the
Mt. Chokai-Tobishima Geopark <Information>
- Phone number: 0184-62-9777 (Mount Chokai-Tobishima Geopark Promotion Council Secretariat)
- URL:Chokaisan-Tobishima Geopark
Lava dome Shinzan, the site of a violent explosion

Shinzan is a lava dome formed during a massive eruption of Higashi-Chokai-yama in 1801, and it stands 70 meters above the crater floor.
It is possible to climb up to Shinzan, and it takes about 5 hours and 30 minutes from the Ohira entrance (Yuza Town, Yamagata Prefecture) or the Hokodate entrance (Nikaho City, Akita Prefecture) of the hiking trail, or about 20 minutes from Omuro Hut (Omuro Sanrojo/accommodation facility) next to the main shrine at the summit of Chokaisan Omonoimi Shrine
A large rock near the main shrine at the summit weighs 300 tons and is a volcanic bomb that was dropped when the new mountain was born. It tells us how violent the eruption was
Lake Chokai, a crater lake filled with meltwater

Lake Chokai (also known as Tori no Umi or Torinoumi) is a crater lake located about 3km west of Shinzan (East Chokai) and at an altitude of about 1,600m on West Chokai
It has a diameter of about 200m and is oval-shaped, elongated from north to south. The water comes from melted snow, and in the harsh winter it is a rare lake where the lake freezes all the way down to its bottom, which is 4.7m deep. Nearby is Tori-no-umi Mihama Shrine, and the Mihamagoya (Mihama Sanrosho) accommodation facility
Normal faults running down the mountainside of Mt. Chokai

The slopes of Mt. Chokai are home to a group of active faults typical of volcanoes. Many of these faults are found from the horseshoe-shaped caldera of Nishi-Chokai to the middle of the western slope, and in the area called Gassan-Mori (1,650m)
The active faults on Mount Chokai are normal faults, which are commonly found in Kyushu, Japan, and are rare in northern Japan.The fault on the western slope is called the Araizawa Fault, and a cliff with a maximum drop of approximately 30m continues for 2.5km. The Gassanmori Fault has a maximum drop of approximately 50m and is 1.5km long.
The Shonai Plain Eastern Edge Fault Zone stretches in a straight line for 35 km

A network of active faults runs along the edge of the Shonai Plain.the Shonai Plain Eastern Edge Fault Zone, it extends about 35 km south from Yuza Town at the foot of Mount Chokai to Sakata City, Shonai Town, and Tsuruoka City.
As of 2022, the probability of an earthquake occurring within the next 100 years on the Shonai Plain Eastern Edge Fault Zone is 0% in the north and less than 20% in the south (Announced on October 19, 2009 by the Earthquake Headquarters, Earthquake and Disaster Prevention Research Division, Research and Development Bureau, Ministry of Education, Culture, Sports, Science and Technology). However, it is said to have caused the Shonai earthquake of 1894 (Meiji 27) in the past, so it is still an active fault and requires careful vigilance
The abundant waters of Mt. Chokai that nourish the Shonai Plain

The Motomachi district in the center of Yuza Town is located on an alluvial fan of the Gekko River, which originates from Mt. Chokai, and is extremely rich in groundwater. As a result, water gushes out when a well is dug, with about 300 wells in total, and the amount of water that gushes out is 4,200 tons per day
a walking course along the Gekko River starting from Yuza Station The Yuza Motomachi Spring Water Group (Town Walking Park), allows you to freely sample 14 artesian wells, courtesy of their owners. However, while the water has been tested and approved, it is not sterilized, so drinking it is at your own risk.
Yusa Motomachi Springs <Information>
- Facility name: Yuza Motomachi Springs (Machi Meguri Park)
- Location: Yuza Town, Yamagata Prefecture, near JR Yuza Station
- Phone number: 0234-72-5666 (Yusa Chokai Tourism Association)
- URL:Machimeguri Park
"Miko no Mizu" - a blessing from the sacred mountain that is essential to life

no Mizuis a washing area that utilizes spring water located in the Mega settlement of Yuza Town.
Mega is a coastal village where the foot of the sacred mountain, Mt. Chokai, sinks into the Sea of Japan, and the spring water is named "Shinsen no Mizu" (Water of the Divine Spring) because it is drawn from the sacred mountain. The spring water is divided into six tanks and separated according to its use
Miko no Mizu <Information>
- Facility name: Miko no Mizu
- Address: 64 Mega, Fukiura, Yuza-machi, Akumi-gun, Yamagata Prefecture
- Phone number: 0184-62-9777 (Mount Chokai-Tobishima Geopark Promotion Council Secretariat)
- access
- By car: Take the Yamagata Expressway to Sakata Minato IC and head towards Akita on National Route 7 for approximately 25 minutes
- Train: About a 5-minute walk from Mega Station on the JR Uetsu Main Line
- Toilets: None
- Parking: None
- URL:Miko's Water
Google Map
Ushiwatari River and Maruike Pond, formed by spring water

The Ushiwatari Riveris a short river, about 4 km long, located at the foot of Mount Chokai on the Sea of Japan side, and almost 100% of its flow comes from springs. The water temperature remains around 11°C throughout the year, and salmon swim upstream in the autumn.
Maruike-sama is a spring-fed pond located near the Ushiwatari River, approximately 20 meters in diameter and 3.5 meters deep. It is one of the sources of the Ushiwatari River, and on its banks stands Maruike Shrine, which enshrines Maruike-sama as its sacred object
Ushiwatari River and Maruike Pond <Information>
- Facility name: Ushiwatari River and Maruike Pond
- Phone number: 0234-72-5666 (Yusa Chokai Tourism Association)
- access
- By car: Take the Yamagata Expressway to Sakata Minato IC and head towards Akita on National Route 7 for approximately 25 minutes
- Train: Approximately 5 minutes by car from Fukiura Station on the JR Uetsu Main Line
- Toilets: Available (temporary)
- Parking: Available (free)
Google Map
Chokaisan Omonokimi Shrine, which enshrines the sacred mountain of Mt. Chokai

Chokaisan Omokimi Shrineis a shrine where prayers were offered to appease the wrath of Mount Chokai, and it is said to have been founded in 564 (the 25th year of Emperor Kinmei's reign), during the late Kofun period. The main shrine, Chokaisan Omokimi Shrine, is located on the summit of Mount Chokai near Shinzan, and there are two lower shrines called "Kuchinomiya" at the foot of the mountain: Fukura (Chokaisan Omokimi Shrine Fukura-guchi no Miya) and Warabioka (Chokaisan Omokimi Shrine Warabioka-guchi no Miya).
During the late Heian period, it was ranked as the Ichinomiya of Dewa Province and is the highest ranking shrine in the country. The main hall on the summit is rebuilt every 20 years, just like Ise Grand Shrine
Mount Chokai Omonokimi Shrine Summit Main Hall <Information>
- Facility name: Mount Chokai Omonokimi Shrine, main shrine at the summit
- Location: Mount Chokai summit
- Phone number: 0234-77-2301
- Official URL:Chokaisan Omokimi Shrine
Google Map

Mount Chokai Omonoki Shrine Fukiuraguchinomiya <Information>
- Facility name: Mount Chokai Omonoki Shrine Fukiuraguchinomiya
- Address: 1 Fukiura Nunokura, Yuza-machi, Akumi-gun, Yamagata Prefecture
- Phone number: 0234-77-2301
- Official URL:Chokaisan Omokimi Shrine
Google Map

Chokaisan Omonoki Shrine Warabiokaguchinomiya <Information>
- Facility name: Chokaisan Omonoki Shrine Warabiokaguchinomiya
- Address: 51 Matsugaoka, Kamiwarabioka, Yuza-machi, Akumi-gun, Yamagata Prefecture
- Phone number: 0234-77-2301
- Official URL:Chokaisan Omokimi Shrine
Google Map
Sixteen Rakan Rocks carved into lava as a memorial for those who died in a maritime accident

The Sixteen Arhat Rocksare rock-carved Buddhist images carved into lava flows from Mount Chokai, located on the coast near Fukiura Fishing Port on the Sea of Japan. A total of 22 Buddhist figures are carved into the rock, including 16 Arhat statues (saints who have reached the highest level of spiritual training), as well as Manjushri Bodhisattva and Samantabhadra Bodhisattva.
The rock-carved Buddha was carved mainly by the priest Kankai of Fukiura Kaizenji Temple as a memorial for fishermen who died in shipwrecks and to pray for safety at sea, and was completed in 1868
16 Rakan Rocks<Information>
- Facility name: Sixteen Rakan Rocks
- Location: Nishidate, Fukiura, Yuza-machi, Akumi-gun, Yamagata Prefecture
- Phone number: 0234-72-5666 (Yusa Chokai Tourism Association)
- Free admission
- access
- By car: Approximately 15 minutes from Yusahiko IC on the Nihonkai Tohoku Expressway
- Train: Approximately 15 minutes on foot from Fukiura Station on the JR Uetsu Main Line
- URL:16 Rakan Rocks








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