Ikeda Caldera & Yamagawa 池田・山川 - Kagoshima - 3/10 & 3/11/2025

My Experience - The experience over this region lasted a couple of days visiting several points around the Ikeda Caldera and Lake, additionally visiting and staying the night in the van at Unagiike (Lake) and Onsen area, as well as visiting the town of Yamagawa and several points in an around Ibusuki area. Detailed blog post here: https://volcanicjapan.com/my-experien...

This overall region is in Kagoshima however geologically, volcanically, is also named according to the Ikeda Caldera, Ibusuki Volcanic Fields, and/or Ata Caldera with more details provided below.

There was not any hiking for this area specifically other than Mount Kaimondake which I hike on 3/12/2025. Most of my travels and observations in this area were largely being in the presence of specific volcanic sites and points of "my" interest. To the unsuspecting traveler or even to most inhabitants that live through the Kagoshima region, although they are familiar with the reality of living in a volcanically active region, many don't often realize the significance of the specific locations they live.

Overall, amazing trip to Kagoshima and this entire area. The people were incredibly friendly, more engaging in southern Japan. I found many if them to have some of the biggest, welcoming smiles and interactions.

The food of this region is also quite amazing, lots of coffee, brown cane sugar from many of the southern islands administered by and included in Kagoshima prefecture. Additionally black pork Kurobuta is well known in this area.

Demographics
Volcano No.- K26
Volcano name- Ikeda
Geologic code - Q3a
Main activity period - Holocene
Activity period / recent activity - From 6,500 yBP.
Latest eruption - 4,900 yBP (Nabeshima Dake)
Volcano type - Caldera, Lava dome, Pyroclastic cone（maar）
Representative rock type - Felsic
Main rock type - Rhyolite, Dacite, Andesite
Height above sea level - 256 m (Nabeshimadake)
Active volcano name by JMA - Ikeda and Yamagawa
Record of eruption & disaster - See below history...
Source: Geological Survey of Japan (GSJ)

About
Ikeda Caldera (池田カルデラ, Ikeda karudera), is a volcanic caldera filled now with Lake Ikeda and associated with the older Ata Caldera on the Satsuma Peninsula.

The Ikeda volcano produced about 20,000 years before present the Iwamoto tephra layer found right around the region of Kagoshima Bay but not further. It later erupted Senta lava before about 7300 years ago erupting the Kikai-Akahoya tephra. The caldera-forming eruptions began 6400 years ago involving by the time they had finished about 5 km3 (1.2 cu mi) of magma and produced local pyroclastic deposits and the Ikezaki tephra. In subsequent magmatic eruptions fall deposits were created of Osagari and Mizusako scoria and Ikeda pumice. The present caldera was formed 4800 years ago when the Ikeda ignimbrite erupted that reached the eastern and western sides and southern tip of the Satsuma Peninsula. This was followed by later eruptions including the Ikedako tephra and those from a fissure vent line southeast of the caldera that produced the pumiceous Yamagawa base surge. A central lava dome was formed within the caldera during the late stage of these eruptions. About 2,800 years ago on part of the margin of the caldera rim the andesitic Nabeshimadake lava dome was formed. During the caldera forming events, and after, about 2.5 km3 (0.60 cu mi) of ignimbrite and 7 km3 (1.7 cu mi) of tephra was erupted with each of the tephra deposits reaching into the Ōsumi Peninsula due to the prevailing winds.

Ata Caldera (阿多カルデラ, Ata karudera), containing the Ata North Caldera, Mount Kaimon and Ikeda Caldera amongst other volcanoes, is a massive, ill defined, mostly submerged volcanic caldera associated with the southern portions of Kagoshima Bay.

Ibusuki Volcanic Field - The Ibusuki volcanic field, also known as the Ibusuki Volcano or Ibusuki Volcanic Group (指宿火山群), is an area of current volcanic and geothermal activity at the tip of the Satsuma Peninsula, Kagoshima prefecture, Kyushu, Japan. It is administered as part of Ibusuki City and Kirishima-Kinkowan National Park.

Geothermal - There are about 800 hot springs within 5 km (3.1 mi) of the sea at the southeastern tip of the Satsuma Peninsula. The relatively recently commissioned Yamagawa Binary Power Station uses local geothermal power to generate up to 4990 kW.

Geological Summary
"Ikeda and Yamagawa" is located at the southeast edge of Kagoshima Prefecture's Satsuma Peninsula. The name is used to refer to the Ikeda caldera, with a diameter of approximately 4 km, the Matsugakubo, Ikezoko, Unagiike, and Yamagawa maar group, and the Nabeshimadake lava domes at the southern rim of the Ikeda caldera. The active volcano, Kaimondake, is located to the southwest of the Ikeda caldera. The SiO2 contents of the erupted materials from those vents are ranging from 56.3 to 72.7 wt %