5th International UNESCO
Conference on Geoparks

Short Introduction of the Geopark Information

Unzen Global Geopark occupies the entire region of the Shimabara Peninsula in the western part of Kyushu Island, Japan. The gentle slopes of Mount Unzen, an active volcano situated at the center of the peninsula, extend radially from the summit area to the coastlines. This mountainous terrain and slopes are cut by multiple faults that roughly trend east to west. The combination of an active volcano and faults suggest dynamic shifting of the Earth on this peninsula. The word Shimabara means island and field in Japanese, which likely refers to the landscape of this peninsula. Unzen or Unzendake are interpreted as clouds and immortals on a mountain and were renamed in 1934 when it was designated as the first National Park of Japan. The region's original name was Onsen-dake, which means a mountain with hot springs.

About 4.3 million years ago, a submarine volcanic eruption formed the basement of Shimabara Peninsula, the main structure of which was formed by successive volcanic activity. Faults visible on the surface were active at least 200,000 years ago. Such dynamic geological phenomena created the beautiful landscapes of the present Shimabara Peninsula.

Volcanic sediments deposited over hundreds of millions of years created the peninsula's relatively smooth topography and gentle slopes. Soil developed from sediment provides excellent drainage for local farming, and the sea surrounding the peninsula offers numerous prospects for fishermen. Residents of the Shimabara Peninsula have taken advantage of these environments for about 30,000 years to foster the industries of agriculture and fishery.

Although society was adversely affected by the eruptions of Mount Unzen, recovery from the devastation was remarkable through the culture and history of peninsula's residents. On the Shimabara Peninsula, one can experience "coexistence of volcano and people," which is the main theme of the Geopark Information .

 

 

Main Geosites in the Geopark Information

Chijiwa fault - the largest active fault in Shimabara Peninsula. This fault was formed by north and south tearing of the peninsula's basement. The maximum displacement, accumulated for 300,000 years, reaches 450 m; displacement has occurred at a rate of 1.5 mm/y.
Unzen Jigoku - geothermal area of the mountain. Unzen Spa offers a sulfur spring composed of acidic volcanic gases released from magma mixed with rainwater and groundwater. The presence of hydrogen sulfide gas odors combined with the hot water burbling out of the ground is a powerful presentation, earning comparisons to a Jigoku (hell).
Obama Spa - one of the hottest springs in Japan. This chloride spring is composed of volcanic chlorine gas released from magma mixed with seawater and groundwater. The source of this hot spring lies nearest to the magma reservoir of Unzen Volcano. In some areas, the springs reach 100 degrees Celsius with the production rate of more than 8,000 ton/day.
Hayasaki basalt - the oldest rock on Shimabara Peninsula. About 4.3 million years ago, submarine volcanic eruption began here. Interaction of basaltic magma with seawater caused successive violent explosions, which resulted in the formation of a small mountain above sea level upon which lava flowed repeatedly.
Basement of Hara Castle - pyroclastic-flow deposits from Aso Volcano. A caldera-forming eruption of Mount Aso in central Kyushu about 90,000 years ago produced large-scale pyroclastic flows traveling as far as 150 km. One such flow formed a plateau upon which Hara Castle stands. This region provided a stage for the Shimabara Rebellion, a ferocious battle in 1637, in which mainly Christian peasants rose to revolt against their brutal feudal load.
Shimabara Springs - water springs around which culture has developed. Since the city of Shimabara is located at the foot of Mount Unzen, abundant water flows from the ground. These springs originated as rainfall on the mountain area that traveled inside the volcano for a long time. The residents of Shimabara take advantage of this precious gift for daily activities such as drinking, cooling, cooking, washing, and sightseeing.
Mayuyama - collapsed mountain, Shimabara Taihen Higo Meiwaku (Shimabara catastrophe). The eastern part of Mount Mayuyam, located west of the Shimabara castle town, collapsed on May 21, 1792, triggered by heavy shaking from a shallow earthquake that occurred soon after an eruption of Mount Unzen. When the mountain collapsed, debris of mountain swept part of the ancient town and rushed into the Ariake Sea. Its entrance into the sea generated tsunamis bout 10 m high that engulfed the opposite shore of the Ariake Sea at the present Higo District of Kumamoto, and the ebbing waves attacked the shores of the peninsula. Small pieces of the collapsed mountain body left by the tsunami created the unique landscape of small hills and islets, called Nagare-yama or hummocky surface.
Heisei Shinzan - the youngest mountain in Japan. This mountain, a huge dome created by sticky dacite lava that heaped on a crater during the eruption in 1991-95, was designated as a Special Natural Monument in April 2004. Its highest peak is 1,483 m. Because the surface of Heisei Shinzan is covered with unstable lava blocks, the area is off limits, and climbing is prohibited.
Mount Unzen Disaster Memorial Hall, "Gamadas Dome" This hall houses the most unique museum in Japan and allows visitors to witness the dangers of volcanic phenomena and to learn lessons from the natural disaster. This museum is the core facility of the Geopark Information .
Tatsuishi Coast - the beginning and growth of Unzen Volcano. Unzen Volcano's activity began around 500,000 years ago. Geologic formations found at Tatsuishi Coast reveal Unzen Volcano's behavior and growth. Eruption in the beginning stage of the volcano was violent as characterized by the products of frothy magma. The activity became less violent with time, as evidenced by the region's dominant lava flows and domes. Most of the mountain peaks in the Shimabara Peninsula are composed of thick lava flows or domes.
Nita pass - Lookout for Heisei Shinzan, a new mountain of lava formed in the last eruption. Nita Pass Observatory and Nita Pass Daini Observatory offer panoramic views of a landscape created as a result of the eruptions of Unzen Volcano. They are the best viewing points on the Shimabara Peninsula where the landscapes of Aso Volcano and Sakurajima Volcano can also be enjoyed.
Ruin of Former Onokoba elementary school - where buildings were burnt during the last eruption. The Onokoba Elementary school building was consumed by a strong, hot ash cloud (pyroclastic surge) that was accompanied by a large pyloclastic flow and was burned out. To pass down the memory of the violence of the pyroclastic surge, this school building is preserved and exhibited intact. A surviving ginkgo tree still grows in the playground area though.
Mizunashi River Memorial Park - a park of houses destroyed by Debris Flow. Many houses and fields around Mizunashi River were buried due to large scale debris flows during the Heisei eruption. In this park, 11 buried houses are preserved and exhibited covered with a large tent.
Senbongi Observatory - outcrops and pyroclastic flows. There were three towns and over 180 houses in Senbongi region. The area, however, was devastated by the large pyroclastic flows that intermittently occurred on June 23 and 24, 1993. From the Observatory, we can see the plain caused by deposition of pyroclastic flows and destroyed houses in the forest.
Taruki Height - a nature restoration area. The area around Heisei Shinzan Nature Center was deserted completely by Heisei eruption. Now, it is a valuable place where the state of subsequent vegetation restoration can be observed. In addition, a walking trail has been built. Visitors can see the strata of pyroclastic flows produced by the Heisei eruption at the side of the trail. The eruption time of each straum has been identified.

 

For further information on Unzen Volcanic Area Global Geopark, please visit the website below.

http://www.unzen-geopark.jp/en-top