is the largest active
volcano3. Conduit
4. Base
5. Sill
6. Dike
7. Layers of ash emitted by the volcano
8. Flank| 9. Layers of lava emitted by the volcano
10. Throat
11. Parasitic cone
12. Lava flow
13. Vent
14. Crater
15...
in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, and is among the largest in the world. It stands in
Kumamoto Prefectureis a prefecture of Japan located on Kyūshū Island. The capital is the city of Kumamoto.- History :Historically the area was called Higo Province and was renamed to Kumamoto Prefecture during the Meiji Restoration as part of the abolition of the feudal system...
, on the island of
Kyūshūor Kyushu is the 3rd-largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include Kyūkoku , Chinzei , and Tsukushi-no-shima...
. Its peak is 1592 m above
sea levelMean sea level is the average height of the ocean's surface ; used as a standard in reckoning land elevation.- Measurement :...
. Aso has one of the largest
calderaA caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption such as the ones at Yellowstone National Park in the US and Glen Coe in Scotland. They are sometimes confused with volcanic craters. The word comes from Portuguese caldeira, and this...
in the world (25 km north-south and 18 km east-west). The caldera has a circumference of around 120 km (75 miles), although sources vary on the exact distance.
The central cone group of Aso consists of five peaks: Mt.
is the largest active
volcano3. Conduit
4. Base
5. Sill
6. Dike
7. Layers of ash emitted by the volcano
8. Flank| 9. Layers of lava emitted by the volcano
10. Throat
11. Parasitic cone
12. Lava flow
13. Vent
14. Crater
15...
in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, and is among the largest in the world. It stands in
Kumamoto Prefectureis a prefecture of Japan located on Kyūshū Island. The capital is the city of Kumamoto.- History :Historically the area was called Higo Province and was renamed to Kumamoto Prefecture during the Meiji Restoration as part of the abolition of the feudal system...
, on the island of
Kyūshūor Kyushu is the 3rd-largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include Kyūkoku , Chinzei , and Tsukushi-no-shima...
. Its peak is 1592 m above
sea levelMean sea level is the average height of the ocean's surface ; used as a standard in reckoning land elevation.- Measurement :...
. Aso has one of the largest
calderaA caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption such as the ones at Yellowstone National Park in the US and Glen Coe in Scotland. They are sometimes confused with volcanic craters. The word comes from Portuguese caldeira, and this...
in the world (25 km north-south and 18 km east-west). The caldera has a circumference of around 120 km (75 miles), although sources vary on the exact distance.
Geology
The central cone group of Aso consists of five peaks: Mt. Neko, Mt. Taka, Mt. Naka, Mt. Eboshi, and Mt. Kishima. 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 and 1989-1991.
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
Asois a city located in Kumamoto Prefecture, Japan.The city was formed on February 11, 2005 from the merger of the former town of Aso with the municipalities of Ichinomiya and Namino from Aso District....
as well as Aso Takamori-cho and South Aso-mura. The
sommaA somma volcano is a volcanic caldera that has been partially filled by a new central cone. The name comes from Mount Somma , a stratovolcano in southern Italy with a summit caldera in which the cone of Mount Vesuvius has grown.A number of the world's best examples of somma volcanoes are found on...
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 90,000 years ago covers more than 600 km³ and roughly equals the volume of Mt. Fuji; it is presumed that the
pyroclastic flowA pyroclastic flow is a common and devastating result of certain explosive volcanic eruptions. The flows are fast-moving currents of hot gas and rock , which travel away from the volcano at speeds generally as great as 700 km/hr . The gas can reach temperatures of about...
plateau covered half of Kyūshū.
History
The eruption which formed the present somma occurred approximately 300,000 years ago.
Four large-scale eruptions (Aso 1 – 4) occurred during a period extending from 300,000 to 90,000 years ago. As large amounts of pyroclastic flow and
volcanic ashVolcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
were emitted from the volcanic chamber, a huge depression (caldera) was formed as the chamber collapsed. The fourth eruption (Aso 4) was the largest, with volcanic ash covering the entire Kyūshū region and even extending to Yamaguchi Prefecture.
Mt. Taka, Mt. Naka, Mt. Eboshi, and Mt. Kishima are cones formed following the fourth above-mentioned huge caldera eruption. Mt. Naka remains active today. It is presumed that Mt. Neko is older than the fourth huge caldera eruption.
Aso's pyroclastic flow deposits (welded tuff) were utilized for bridge construction in the region. There are approximately 320 arched stone bridges in
Kumamoto Prefectureis a prefecture of Japan located on Kyūshū Island. The capital is the city of Kumamoto.- History :Historically the area was called Higo Province and was renamed to Kumamoto Prefecture during the Meiji Restoration as part of the abolition of the feudal system...
, including the Tsujun-kyo and Reidai-kyo bridges on Midorikawa River, which are important national cultural properties.
External links