開聞岳 - Kaimondake - 3/12/2025

Morning photo from Family Mart Parking Lot

My Experience - Kaimondake can be seen from several points across the region. My first views of Kaimondake were when I was hiking Kirishimayama in Miyazaki and seeing the conical shape in the far distance.

I arrived the evening of March 11th, 2025 and took an initial test hike, walking the first 10-15 minutes on the trail.

Trailhead is here by the way: Mt. Kaimon North Trailhead 開聞岳北登山口. As hotel accomodations in the area appeared pricey for the evening, I decided to stay in the Family Mart Parking Lot (or next to it) by some buildings that appeared years from usage: Family Mart; Kaimon-senta ファミリーマート開聞仙田店.

Next morning woke up early, drove the short 5 minutes to the starting point. Thought I was the only person but turns out about 3 people hiking ahead of me. The hike was not as difficult as it is made out to be on AllTrails.

The trail spirals up the mountain a bit later during the hike. Here is my (the) hike route: https://www.alltrails.com/explore/recording/morning-hike-at-mount-kaimondake-dbb4229

Demographics

Volcano No. - K27

Volcano name - Kaimon Dake

Geologic code **Q3b

Main activity period - Holocene

Activity period / recent activity ***From 4,500 yBP.

Latest eruption: AD 885

Volcano type - Composite (compound) volcano, Lava dome

Representative rock type - Mafic

Main rock type ****Basalt, Andesite

Height above sea level - 922 m

Location (Prefecture)KAGOSHIMA - Latitude (WGS84)31.1800E. Longitude (WGS84)130.5283

Active volcano name by JMA Kaimondake

Record of eruption & disaster

- Ca. 2 Ka: Subplinian eruption: Scoria fallout.

- 7th century: Subplinian and phreatomagmatic eruptions: Scoria fallout.

- 29 Mar 874: Subplinian eruption: Scoria fall and lahar.

- Aug, Sep 885: Subplinian eruptions: Scoria fallout; lava dome. 

Additional comments 

Source: GSJ

About

Kaimondake (開聞岳, Kaimon-dake), or Mount Kaimon, is an undissected volcano – consisting of a basal stratovolcano and a small complex central lava dome – which rises to a height of 924 metres above sea level near the city of Ibusuki in southern Kyūshū, Japan. The last eruption occurred in the year 885 CE. Because of its conic shape, Mt. Kaimon is sometimes referred to as "the Fuji of Satsuma". It is one of the 100 Famous Japanese Mountains.

Geography - Mt. Kaimon is located in the south of Kagoshima prefecture, Kyushu and is an important reference point for marine traffic because it is the southernmost prominence of the Satsuma Peninsula. This is one entrance marker to Kinko Bay (Kagoshima Bay) complimentary to the Ōsumi Peninsula. Together with Mt. Noma and Mt. Kinpo, it is used by marine traffic.

Geology - Part of the Ibusuki volcanic field, Mt. Kaimon defines the eastern margin of the old Ata Caldera. The total eruptive volume of tephra has been 3.1 km3 (0.74 cu mi) and 2.3 km3 (0.55 cu mi) of lava.

There is a sea scarp which is 7.8 km wide and 9.3 km long, the shape is similar to a horseshoe in the seabed at the southern foot of the mountain. There is a lot of sediment at the foot of the mountain due to submarine landslides. It was found that there is a sea scarp underground on the south side of the mountain and it was caused by pressure from a submarine landslide before Mt. Kaimon was formed.

The sedimentary layer of ejecta from the eruption at the end of the 7th century is called ao-kora (ao means blue and kora is soil consisting of volcanic ash found in the southern part of the Satsuma Peninsula). The sedimentary layer of ejecta by the eruption at the end of the 7th century is called murasaki-kora (Murasaki means purple). These layers are a clue to know the changes in life in this era. It has become clear that a village was isolated by a large eruption with change in life style in the latter part of the 9th century. 

Eruptive history - Mount Kaimon began volcanic activity about 4,000 years ago. From 3,000 years up to 885 years ago, large eruptions occurred 9 times and eruptions resulting in large amounts of lava occurred 10 times making twelve major eruptions to date.

The two large eruptions in the historic written record are in 874 CE (Jogan era) and 885 CE (Nin-na era) The complex layered central dome consists of a scoria cone topped by lava flows and ultimately a lava dome which was penetrated by a plug. However the explosion crater at the top was last enlarged by the 885 CE eruption.

Transition of height - In 1895, the official height of Mt. Kaimon was 922.23 m (3,025.7 ft) from a second triangulation point which was at the summit of the mountain, but this was updated to 924 m (3,031 ft) by the Geospatial Information Authority of Japan in July 2001, because climbers pointed out that the height of the rocks on the top of the mountain were higher than the triangulation point.

Climbing - The spiral-shaped hiking trail climb of Mt. Kaimon takes about 3 hours. Mt. Kaimon is considerably lower than most of the mountains on the 100 famous Japanese Mountains list but as climbing starts from close to sea level there is an ascent of 900 metres (3,000 ft). Mt. Kaimon is a single peak but with summit rocky outcrops that allow views on all sides, such as Lake Ikeda to the north and the Pacific Ocean to the south. Source: Wikipedia

Geological Summary

The submerged 15 x 25 km Ata caldera under Kagoshima Bay is one of several large calderas in southern Kyushu and the source of major pyroclastic flows associated with its formation more than 40,000 years ago. The National Catalogue of the Active Volcanoes of Japan (JMA, 2013) included features of the Ibusuki field as part of the Ata post-caldera system. That area consists of numerous central cones and maars, the 4.5-km-wide Ikeda caldera, and Kaimondake stratovolcano. The symmetrical andesitic Kaimondake is the most prominent feature, and is capped by a lava dome. Ibusuki has been very active during the Holocene, forming the Ikeda caldera about 4,600 years ago, numerous maars and lava domes. Kaimondake formed during the last 4,000 years, from which all eruptive activity has occurred after about 2,650 years ago. Its last eruption took place in the 9th century. While listed as features of the Ata caldera, JMA (2013) simultaneously listed Kaimondake and the combination of Ikeda and Yamagawa as distinct volcanoes.

Source: Global Volcanism Program