Mount Aso, near the middle of the island, had one of the largest eruptions ever known 300,000 years ago, and remains a threat.
Japan is one of the most volcanically active locations on Earth
Japan has four main islands and many more which are smaller. The main islands are Hokkaido to the north, Honshu in the center, and Shikoku and Kyushu to the south.
Japan is very volcanically active, and is located where four tectonic plates meet. Besides volcanic activity, the islands are also very prone to earthquakes and tsunamis.
The islands combined are roughly the same size as the state of California in the USA, but have more than triple the population. Over a dozen cities have a million or more residents, and Tokyo - located in the approximate center of Honshu on the Pacific side - is the largest metropolitan area in the world, with about the same population as all of California.
Of the four main islands, three have active volcanoes. Shikoku does not. Below I will give details about those which are found on the island of Kyushu.
For anyone not familiar with basic terms relating to volcanology, the science of volcanoes, I created a separate article with information such as the difference between a crater and a caldera, what shield volcanoes and a stratovolcanoes are, and more.
The 37th largest island in the world, and 3rd largest in Japan, Kyushu has a population of over 13 million. The largest city is Fukuoka, with a metro area of about 5.6 million. Most of the population is located in the northwest part of the island.
The island is mountainous, and includes eight active volcanoes. Mount Aso is Japan’s largest volcano, and has one of the world’s largest calderas. It is responsible for the third most massive volcanic eruption of the past 250,000 years. Interestingly, within the caldera are several towns and a population of about 50,000.
Another volcano discussed below, Mount Unzen, is responsible for the worst-ever volcanic disaster in the history of Japan. The disaster occurred in 1792 and worldwide there are only five volcanic eruption disasters that are known to have been worse.
Mount Unzen and another on this list, Sakura-jima, are on the official list created by the United Nations of the world’s most dangerous volcanoes.
Although Kyushu is less seismically active than the rest of Japan, earthquakes are still fairly common. In 2005 a magnitude 6.6 quake struck near Fukuoka causing a lot of damage and injuring hundreds of people.
Typhoons are a threat every summer and autumn, and heavy rains are frequent during this part of the year. The island’s climate is subtropical and humid.
Kyushu volcano #1 - Fukue-jima
The word “jima” is Japanese for island. Fukue Island is located about 50 miles (80 km) west of the main island of Kyushu.
This shield volcano last erupted in what is estimated to be between 550 BC and 400 BC, and is considered active and likely to erupt again someday. The island has at least five cinder cones associated with the main shield volcano.
Fukue-jima is part of a group of closely packed islands called the Goto Islands. In total there are 140 islands, and Fukue-jima is the largest. All of the islands combined have a population of about 40,000.
Kyushu volcano #2 - Ibusuki Volcanic Field
The Ibusuki Volcanic Field, with Mount Kaimondake visible.
Located at the southern tip of Kyushu, this volcanic field has a caldera, multiple cinder cones and lava domes, and a stratovolcano, and they are all related to one another. Lots of activity has occurred over the past few thousand years, and the most recent eruption is dated at 885 AD.
Evidence suggests that there were numerous eruptions over the centuries prior to this last eruption, and then they suddenly came to a halt. Currently there are hundreds of hot springs in the area, heated by the magma underneath the surface.
The two main features of the Ibusuki Volcanic Field are the Ata Caldera, of which the western half is located underwater and is part of Kagoshima Bay, and Mount Kaimondake, which is the stratovolcano that was mentioned. Occasional earthquake swarms show that this volcano will erupt again at some point.
Kyushu volcano #3 - Mount Aso
Crater lake located within one of the peaks in the Mount Aso caldera.
This is the largest volcano in Japan. Not the tallest, but the largest in physical size with a caldera that measures about 75 miles (120 km) across.
About 90,000 years ago the main caldera was formed in a massive eruption that was so large that only two eruptions since then have been larger worldwide. The two that beat it are eruptions by Indonesia’s Toba Supervolcano 70,000 years ago, and by New Zealand’s Taupo Supervolcano 26,500 years ago.
Mount Aso is one of the largest volcanoes on Earth. Supervolcanic eruptions by definition expel 1,000 cubic kilometers of material, and Mount Aso erupted 600 cubic km, which is 60% of the way there. By comparison, the largest eruption of the past century was Mount Pinatubo in the Philippines in 1991, which erupted 10 cubic km of material.
Located near the center of the island, the volcano is more correctly called a volcanic field or volcanic complex, like Ibusuki discussed above. There are multiple craters, cinder cones, stratovolcanoes, vents, and a lava dome within the large caldera. Five main peaks are located near the center of the caldera, and one crater furthest to the north has been the most active over the past century, with numerous eruptions.
The caldera features a national park and hundreds of hot springs, and is a popular tourist destination.
Kyushu volcano #4 - Mount Kirishima
Stratovolcano located within the Mount Kirishima volcano complex.
Once again, as with Ibusuki and Mount Aso discussed above, this volcano is a complex of multiple volcanoes that are all related to one another. There are over twenty volcanoes total at this location, including stratovolcanoes, cinder cones, and craters.
One of the stratovolcanoes, Shinmoe-dake, has erupted at least six times in the past century, and erupted twice in 2011. Other volcanoes within the complex are also active. For many centuries now, eruptions have occurred regularly and they have all been small to moderate in size. Kirishima is located in the southern part of the island.
Kyushu volcano #5 - Mount Kuju
This complex of volcanoes features a stratovolcano, some cinder cones and craters, and sixteen lava domes. The most recent eruption, which occurred over several months between 1995 and 1996, was the first to occur at this location in 200 to 300 years. Mount Kuju has typically erupted every few hundred years over at least the past 10,000 years.
The most recent eruption was minor in size, and no large eruptions are known to have occurred in the past 2,000 years. Currently two geothermal power plants are located here, northeast of Mount Aso and the center of the island.
Kyushu volcano #6 - Mount Tsurumi
This is a group of lava domes, which sit above the city of Beppu on the northeast coast of Kyushu. The city is known for hot springs resorts, and the hot springs are heated by the magma source for this volcano complex.
The last known eruption was moderate in size and occurred in 867 AD, and historical records indicate that another smaller eruption took place in 771 AD. Other than these, the only other known eruption at this location was moderate in size and occurred about 2,200 years ago.
Kyushu volcano #7 - Mount Unzen
This is a group of several overlapping stratovolcanoes, and is the site of Japan's worst ever volcanic disaster. The disaster occurred in 1792 when one of the stratovolcanoes collapsed after an earthquake, and a giant landslide into Ariake Bay created a wave 330 feet (100 meters) tall.
The wave went across the bay and slammed into Higo Province, then bounced back and added to the damage done by the landslide to the city of Shimabara. Even the returning wave was between 33 and 187 feet (10 and 56 meters) tall depending on where it hit. In total 15,000 lives are estimated to have been lost, with about 10,000 in Shimabara and 5,000 in Higo Province on the other side of the bay.
In 1991 an eruption took the lives of 43 scientists and journalists who were studying the volcano, and overall this volcano is considered one of the most dangerous in the world. Eruptions in the 1990s destroyed about 2,000 homes, and in the area warning systems and evacuation plans are in use.
Kyushu volcano #8 - Sakura-jima
Along with Mount Unzen, this is recognized as one of the world’s most dangerous volcanoes. It is located in the southern part of Kyushu, north of the Ibusuki Volcanic Field discussed above.
Sakura-jima used to be an island in a bay, but is now connected to the rest of Kyushu as a result of frequent ongoing volcanic activity. Just a few miles (kilometers) away the city of Kagoshima hosts over 650,000 residents.
Sakura-jima is what is left of the Aira Caldera, a large volcano that had a massive eruption 22,000 years ago. The stratovolcano sits within this caldera. Ongoing lava flows are a major tourist attraction.
Most of this volcano’s eruptions are smaller and affect the summit mostly, and will spill some lava and possibly deposit thin layers of ash on Kagoshima. However, in the past eruptions as large as what occurred with Mount Saint Helens in Washington, USA in 1980 – or larger – have occurred. It just hasn’t happened in a few hundred years.