Mount Aso — Nakadake Crater

photo by そらみみ · CC BY-SA 3.0

400×900 m: in the crater's emerald-green lake the water is at 50–60°C, and strongly acidic.

You arrive at 阿蘇山上ターミナル, the plaza at the top of the volcano's toll road, with a free car park for 65 cars. The crater itself (a complex of about 400 by 900 metres, with an emerald-green acid lake at the bottom when activity is calm) lies beyond, within the one-kilometre radius that the alert level can close at any moment: from here, when the service is running, a 5-minute shuttle takes you near the rim.

Nakadake is one of the five central peaks (阿蘇五岳) inside the great Aso caldera, and its first crater is among the most closely monitored volcanoes in Japan: sulphurous gas, seismic tremor and the colour of the crater lake are measured every day. The area lies within Aso-Kuju National Park, established in 1934 (as 阿蘇国立公園, renamed in 1986), and within the Aso UNESCO Global Geopark, recognised in September 2014. 2026 was a year of high alert: the level rose to 3 (entry ban, 2 km radius) on 14 August, after an increase in sulphurous gas and volcanic tremor, and went back to 2 on 1 September at 16:00, with the restriction reduced to about 1 km from the crater from 9:00 the next day, when access up to the plaza also became possible again.

ℹ️ ⚠️ Access depends on the volcanic alert level and can close without notice: check on the day on https://www.aso-volcano.jp/ (the site of the volcano disaster prevention committee, with the current 1次/2次/3次 restriction regime kept up to date) and on 気象庁 (JMA) for the level. Today, 03/09/2026, level 2 is in force with 1次規制 (radius of ~1 km closed from 02/09 at 9:00): the plaza/terminal can be reached and is open 9:00–16:30, but the shuttle to the crater rim was SUSPENDED as of 02/09/2026 (source: the operator's official site); it is not guaranteed even when the level would allow it, because it also stops for wind and gas concentration. The park toll road has seasonal hours (summer 8:30–18:00, gate 17:30) and they can be shortened without notice. Night-time access always prohibited.

🚉 Aso Sanjo Terminal · 1 min walk

Sources: jma.go.jp · city.aso.kumamoto.jp · aso-volcano.jp · sankobus.jp · sankobus.jp · aso-geopark.jp · env.go.jp · city.aso.kumamoto.jp · aso-geopark.jp

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