Can You Visit the Aso Crater Now? Alert Level 2, Gas and the Mountain Road

Published 2026-10-04 · Sources checked 2026-10-04 · Treasure Hunting Co., Ltd.

This guide is for visitors who want to see the crater of Mount Aso, and need to know whether they can on the day they travel. On 2026-10-04, the Japan Meteorological Agency listed Aso at eruption alert level 2, and the city of Aso said that crater viewing was not possible. This guide explains what that means and how to check.

We used the Aso city website, the Japan Meteorological Agency (JMA) volcano page, the Aso Volcano Disaster Prevention Council and the Japan National Tourism Organization (JNTO). All pages were read on 2026-10-04. The situation can change quickly, so check the official pages on the day.

What the alert level says today

The JMA page for volcano climbers lists the volcanoes with a current eruption warning. On the day we read it, Aso appeared with a crater-area warning at eruption alert level 2, described there as "crater area restrictions". The same page showed an explanatory bulletin for Aso issued on October 2 at 4:00 PM.

JNTO explains that the JMA issues volcanic warnings and forecasts for about 110 active volcanoes in Japan. It also issues eruption notices, which announce right away that a volcano has erupted, so that people can protect themselves.

What is closed at level 2

The Aso city page on climbing Mount Aso states the rules in plain terms:

• While the crater-area warning at level 2 is in force, crater viewing and entry to Sunasenrigahama are not possible.
• Climbing Takadake and Nakadake is still possible by using a detour route.
• When the level rises to 2, entry is banned within a radius of 1 kilometer of the Nakadake crater. The city names two detour routes, the Sarayama detour and the Suzumeiwa detour.

The city's front page also carried a notice titled "Regarding the ban on entering the area around the crater". It was dated June 12, 2026. We did not find an end date.

Gas is a danger even when the level is low

The Aso Volcano Disaster Prevention Council says the crater is alive, and that eruptions have occurred repeatedly throughout recorded history. It warns that toxic volcanic gases circulate near the crater.

The council says people with asthma, bronchitis or heart problems should avoid the crater area. In its stronger wording, those people are forbidden from climbing at all, because exposure to the gas could result in death.

The council adds that entry zones are restricted depending on how much gas comes out. It asks visitors to pay attention to announcements and to follow the instructions of the crater monitors in an emergency. If gas makes you unwell, tell a crater monitor straight away.

Before you hike on Mount Aso

The Aso city page lists these points:

• Some climbing routes are impassable, or not recommended, because of landslides and cracks from the 2016 Kumamoto earthquakes and from heavy rain.
• Check the latest information from the Aso mountain accident prevention council, which sits inside the Kumamoto prefectural regional office, before you climb.
• Always submit a climbing plan.
• Take great care where volcanic gas is present, and on stretches of poor footing.

The Aso Volcano Disaster Prevention Council also lists the hours of the mountain park road. See our guide to getting to Aso and the crater road for those and the driving directions.

Emergency numbers

• 119, fire and ambulance. JNTO says to call 119 for a fire, and when someone is seriously sick or injured.
• 110, the police. For a traffic accident or a crime.
• Japan Visitor Hotline. JNTO runs this line in English, Chinese and Korean, 24 hours a day, 365 days a year, at 050-3816-2787.

The Fire and Disaster Management Agency says to have your passport, cash or a credit card, and any medicine you take ready when you call for an ambulance. This guide is not an emergency plan. In an emergency, follow the instructions of the authorities.

What we could not verify, and therefore left out

• Whether the alert level is still 2 on the day you read this. Check the JMA page and the city page.
• The current gas readings at the crater.
• Which climbing routes are open today.
• Whether 110 and 119 calls are answered in English.

Related guides

• How do you get to Aso and the crater road?
• What is the Aso caldera? The five peaks and four giant eruptions

Sources

All URLs retrieved 2026-10-04.

1. Mount Aso climbing (Aso City, in Japanese) — (level 2 restrictions; detour routes; climbing notes)
2. Aso City official site, front page (in Japanese) — (notice dated 2026-06-12)
3. Information for volcano climbers (Japan Meteorological Agency, in Japanese) — (alert level list)
4. Precautions when climbing the mountain (Aso Volcano Disaster Prevention Council) — (toxic gas; people who must not climb)
5. Safety tips for travelers (Japan National Tourism Organization) — (volcanic warnings and eruption notices)
6. For safe travels in Japan - Guide for when you are feeling ill (Japan National Tourism Organization) — (119 and 110; Japan Visitor Hotline)
7. Guide for Ambulance Services (Fire and Disaster Management Agency) — (what to prepare)