Spectacular Volcanic Caldera in Mount Aso in Kumamoto

As the largest active volcano in Japan and one of the largest in the world, Mount Aso in Kumamoto Prefecture (on Japan’s southern island of Kyushu) is an awesome feat of nature that is definitely worth a trip for any visitor to Japan. A little bit thrilling and overwhelmingly beautiful, visiting Mount Aso is definitely one of the best things to do in Kyushu! The rugged beauty of its landscape will make you feel as if you are walking on the moon!

Mount Aso’s Geographical Features

Mount Aso is famous for its huge caldera. A caldera is a large bowl-shaped depression which results from the emptying of a volcano’s magma chamber during a volcanic eruption and the surrounding land subsides to fill this gap. Mount Aso’s caldera is over 16 miles (25 km) north to south and 11 miles (18 km) east to west and has a circumference of around 75 miles (120 km). Did you know the word caldera is actually derived from the Portuguese word for cauldron? The caldera at Mount Aso formed during caldera eruptions 90,000 to 270,000 years ago, the final and largest of which reached as far away as Yamaguchi Prefecture which is 167 miles (270 km) away.

More interestingly, the pyroclastic flow deposits, the stuff that comes out of the volcano when it erupts, from Mount Aso were used for bridge construction. There are approximately 320 arched stone bridges all across Kumamoto Prefecture, including the Tsujun-kyo and Reitai-kyo bridges on the Midorikawa River. These bridges are important national cultural properties.

Walk Around the Volcanic Crater

Make sure to check the volcano's current state before your visit. During times of heightened volcanic activity, the crater can be off-limits, the ropeway not operating, and the road and walking trail to the crater would be closed. Following the eruption in 2016, the no-entry zone around Mount Aso's crater was lifted on April 24, 2018, so it is now possible to view the crater again (permitting that the gas levels are low enough to be deemed safe). Unfortunately, the cable car ropeway to the crater still remains out of service due to earthquake damage. However, a shuttle bus operates between the ropeway's lower station and the crater so visitor may view the crater. This is 1,200 yen for a round trip. The toll road to the crater is also open to regular cars (compact cars: 600 yen, normal cars: 800 yen) so you can drive up to the crater (as of Spring 2018) or use the loop shuttle bus services.

If you can get to the crater it is well worth it! The views are amazing, and looking into the emerald lake of one of the world’s most active volcanoes is pretty special. Also, if you have time take a walk around the other craters and take in the black sand you’ll have an opportunity to see, what I can only imagine, Mars must look like! The peaks of Mount Aso at night are said to resemble a reclining Buddha so if you do go hiking keep an eye out for the reclining Buddha! This is truly a unique experience you can only do in Japan, the land of volcanoes!

Try the Incredibly Clear Water From the Caldera

Water of Shirakawa river, the class A river that runs through Kumamoto City, comes almost entirely from the rain that fell in the caldera and the spring water in the upstream area. Rain in the middle basin soaks into the ground and does not flow into the river so much, therefore it is said that Shirakawa River has the water from the caldera of Mount Aso. In its upper stream lies the famous Shirakawa water source – rated as one of the clearest waters in Japan in 1985 by the Ministry of the Environment. Every minute 60 tons of water well up and immediately become a river 5-meter wide, running down to Kumamoto City!

The mineral content of the water is around 72 - 97mg per liter, which is a little higher than the average water hardness in Japan. Due to its rich water supply, the Shirakawa water source has been appreciated by local people as a non-depleting water source for many years. This can be seen at the Shirakawa-yoshimi Shrine, a shrine located next to the water source. From a long time ago, people in Kumamoto has worshiped the “God of water” and appreciated the endless supply of clear water. Even today, you can actually taste the water and enjoy the blessing of the fertile nature in Kumamoto. If you have a container, you can also take some water back to enjoy at home. The water tastes amazing especially after seeing the Mount Aso’s caldera in person!

Exercise, Eat and Relax at Aso Farm Land – the World’s First “Health Theme Park”

After spending time enjoying Mount Aso’s caldera and the water source, why not plan a fun day trip to Aso Farm Land? It is a large theme park developed in cooperation with health experts with the purpose of providing a healthy lifestyle. The park consists of the following elements: