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Unzen Volcanic Area Geopark
Unzen Volcanic Area Geopark[1]
Location
Unzen Volcanic Area Geopark is located in the southern region of Kyushu’s Nagasaki Prefecture on the western end of Japan. The Geopark is limited by the administrative district of the three cities (Shimabara, Unzen and Minamishimabara), almost the same area as the Shimabara Peninsula. The area is located approximately 900km, or four hours by air and bus, from Tokyo, and approximately 100km, or three hours by car, from Kyushu’s largest city, Fukuoka.
Earth Sciences of the Shimabara Peninsula
Before the Unzen Volcano developed, the Shimabara Peninsula area was shallow sea. The strata deposited in this shallow sea is know as the “Kuchinotsu Group”. Visitors can view them in the south of the peninsula. While the “Kuchinotsu Group” was forming, volcanic activities were also occurred in situ. Now a gentle slope remains in the southern area formed by these eruptions,e.g. mainly low-viscous basaltic lava flows. Unzen volcano is located in the center of the peninsula and many lava domes have been formed by viscous dacite magma.
Human History
Shimabara Peninsula is known for a number archaeological sites, such as Unzen City’s Hyakkadai remains from the Paleolithic Age, and Shimabara City’s Onobaru and Obarushimo remains, and Minamishimabara City’s Harayama and Gongenwaki remains from the Jomon Period (10,000 BC – 400 BC). In particular, remains from the latter part of the Jomon period, such as Yamanotera remains and Gongenwaki remains of Minamishimabara City, clearly point to an advanced cultural life, suggesting the emergence of rice farming before the Yayoi period (400 BC – 300AD).
Tectonics around Shimabara PeninsulaThe narrow region extending from near Beppu City to Shimabara Peninsula is characterized by abundant normal and strike slip faults roughly extending EW to NE-SW. This region in known as the Beppu-Shimabara Graben. Unzen is a volcano that has developed within one of these active basins (Unzen Graben).
Special features of the Unzen Volcanic Area Geopark [2]
The foremost feature of the Unzen Volcanic Area Geopark is the opportunity it affords for learning about the coexistence of people and volcanoes, based on the damage caused by the two major eruptions of the past, and how the local people subsequently rebuilt the region. In terms of geological characteristics, the oldest part of the Shimabara Peninsula is the 40 million-year-old stratum of which a very small portion is exposed in the southern part. A layer of magma and pyroclastic material dating back around 4.3 million years, and a stratum built up from the seas to the land covers this. On top of this is a thick coating of ejecta from Mount Unzen that began to emerge in the center of the peninsula around 500,000 years ago. Moreover, not only does the Shimabara Peninsula enjoy geodiversity with its volcanic topography and its fault topography, as typified by the Chijiwa fault, it has also experienced two major volcanic disasters. The first was the 1792 Shimabara Disaster, in which 15,000 people throughout the Ariake region died in a single night, Japan’s worst single volcano catastrophe. The second was the Unzen Fugendake Disaster of 1990 to 1995, the pyroclastic flow of which resulted in 44 dead and missing persons and considerable damage to the region. However, few people moved away from the region as a result of the disaster, and there are still around 150,000 residents living in tandem with the volcano. Furthermore, Mount Unzen Fugendake is also famed as one of the most thoroughly studied volcanoes of recent years, as the formation of the magma dome following the Heisei eruption in the 1990s, and part of the beginning and end of the eruption were observed with scientific precision. The Shimabara Peninsula is sprinkled with sites of geological interest including an active volcano and active faults so that we can make a field trip around such various noteworthy places. Geodiversity Geodiversity describes a state in which there is a wide diversity in the geological characteristics of an area (rocks, minerals and fossils etc.), its topography (surface shape, topographical processes) and the natural distribution patterns of its soil quality and features.
Geological map of Mount Unzen and estimates of geological age (based on Watanabe and Hoshizumi 1995 and Hoshizumi et al. 1999)
List of the main geosites in Unzen Volcanic Area Geopark
| Theme | Sub-theme | Geosites |
| Origins of Shimabara Peninsula |
Beginnings of Shimabara Peninsula | Hayasaki Basalt |
| Kunisaki Andesite | ||
| Major eruptions in Kyushu | Hara Castle | |
| Origin of Unzen volcano | Tatsuishi | |
| The Sinking Unzen volcano | Chijiwa Fault | |
| Suwanoike Pond | ||
| People and Volcanic Eruptions |
Pyroclastic flows of the Jomon Period | The Gongenwaki remains |
| Shimabara Taihen (Catastrophe) | Shin’yake lava | |
| Mayuyama Collapse | ||
| Lake Shirachi | ||
| Heisei eruption | Heisei Shinzan (lava dome) | |
| Nita Pass | ||
| Disaster and Restoration | Damage from pyroclastic flows | Remains of Kamikoba |
| Remains of Oonokoba | ||
| Remains of Senbongi | ||
| Damage from debris flows | Memorial park of Houses destroyed by Debris Flows |
|
| Restoration of nature | Taruki Daichi nature restoration area | |
| The Gift from Nature | Hot Springs | Obama Spa |
| Unzen Spa | ||
| Shimabara Spa | ||
| Hot Springs of organic origin | ||
| Groundwater | Abundant springs of groundwater | |
| Vegetation | Maple, Azalea, Enkianthus cemuus, etc. |
[1] http://www.unzen-geopark.jp/image/master-plan-final.pdf