阿蘇山 - Aso - 10/27/2023

My Experience: The previous day I had hiked Mount Unzen in Nagasaki and had stay the evening in Ozu (CANDEO HOTELS Ozu Kumamoto Airport (カンデオホテルズ 大津熊本空港). I love these "business hotels" especially this one as the top floor has a public bath that includes an outdoor bath as well. That evening prior to hiking Aso, I enjoyed dinner at Hamakatsu Kumamoto Ozu とんかつ濵かつ 熊本大津店, a tonkatsu restaurant a short walk from the hotel.

The next morning (morning of 10/27/2023) I departed the hotel at about 7 AM to Aso Sanjo Public Square 阿蘇 山上広場 which is about a 40 minute drive from Ozu. This is the parking lot you are required to park and the start of the trailhead loop called the Sunasenri route Furubochi Trailhead.

You can find my route on #alltrails here: https://www.alltrails.com/explore/recording/morning-hike-at-kusasenri-ga-hama-mount-aso-loop-fc452d0

I skipped the short off shoot Nakadake to Takadake due to lightning (which I have outline below in red). This will add another 2KM to your hike. I would highly suggest doing this in good weather. I unfortunately had to skip for this trip :(

Next Trip: here will be to park at Otonokuchitogetozanguchi Parking Lot (大戸ノ口峠登山口駐車場) and to hike Nekodake across to Taka-dake Touhou (Mt. Taka-dake East Peak) 高岳東峰, the down to Aso which by itself is about 7.25 KM (or about 4.5M) 

About: Mount Aso (阿蘇山, Aso-san), is also known as Aso Volcano and in this sense is the largest active volcano in Japan, and is among the largest in the world. Common use relates often only to the somma volcano in the centre of the Aso Caldera. It stands in Aso Kujū National Park in Kumamoto Prefecture, on the island of Kyushu. Its tallest peak, Takadake, is 1,592 meters (5,223 ft) above sea level. Mount Aso is in a fairly large caldera (25 kilometers (16 miles) north-south and 18 km (11 mi) east-west) with a circumference of around 120 km (75 mi), although sources vary on the exact distance.

The central cone group of Aso consists of five peaks, often called the "Five Mountains of Aso" (阿蘇五岳): Mt. Neko, Mt. Taka (also called Takadake or Taka-Dake), Mt. Naka (also called Nakadake or Naka-Dake), Mt. Eboshi, and Mt. Kishima (also called Kishimadake or Kishima-Dake ). The highest point is the summit of Mt. Taka, at 1592 m above sea level. The crater of Mt. Naka, the west side of which is accessible by road, contains an active volcano which continuously emits smoke and has occasional eruptions. Only the northernmost crater (the first crater) has been active for the last 70 years—1974, 1979, 1984–1985, 1989–1991, 2009, 2011, 2015, 2016 and 2021.

The present Aso Caldera formed as a result of four huge caldera eruptions occurring over a range of 90,000–300,000 years ago. The caldera, one of the largest in the world, contains the city of Aso as well as Takamori and Minamiaso enclosing the caldera extends about 18 km east to west and about 25 km north to south. Viewpoints from the somma overlooking the caldera are perched upon lava formed before the volcanic activity which created the present caldera. Ejecta from the huge caldera eruption 90,800 years ago covers more than 600 km3 and roughly equals the volume of Mount Fuji; with a pyroclastic flow plateau that covered a significant part of Kyushu.

Volcanic ash from Mount Aso and Mount Kujū plays a crucial role in maintaining and replenishing the tidal flats of the Ariake Sea, which are among the largest in Japan. Several of the flats have been designated as Ramsar sites. The ash is carried from the volcanoes to the coastline by the Chikugo River, which has its source located on Aso as well. (Source: Wikipedia)

Geological Summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations. This volcano is located within the Aso, a UNESCO Global Geopark property. (Source: Global Volcanism Program)