山陰海岸ジオパーク





Although Japanese islands used to be a part of the Asian continent, they began to separate from the mainland about 20 million years ago and formed the Sea of Japan. At the San'in Kaigan Geopark, you can find lots of geological assets from the period of the Sea of Japan formation.


Part of the Asian continent

50 million years ago
from 60 million years
The oldest rocks in San'in Kaigan Geopark area were formed approximately 100 million to 60 million years ago, when the Japanese Islands were part of the Asian continent. They remain at Kimonzaki and the granite of the period appears at Uradome Coast, Tainohama Coast, and Ooura Coast.



Uradome Coast
(Iwami, Tottori)
Kimonzaki
(Shin'Onsen, Hyogo)



Beginning of Separation from the Asian continent

19 million years ago
from 23 million years
Approximately 25 million years ago, the eastern margin of the Asian continent started to split due to large-scale crustal movement and volcanic activity. About 25 million years ago a trough was formed and there were freshwater lakes. Andesites erupted from fissures. Andesites of Shishinokuchi were formed during this period.
The Tsuji Conglomerate, composing of the Yodo Sea Cave and Hasakariiwa Rock, was the first to be created and then clastic and pyloclastic rocks of Tajima Sekiheki and Shiraishi Island were formed. Matsugasaki Hyakusogai (hundred-layer cliff) is made of strata with many layers of conglomerate, sandstone, and tuff.



Matsugasaki Hyakusogai(hundred-layer cliff)
(Kami, Hyogo)
Tajima Sekiheki
(Kami, Hyogo)



Shishinokuchi
(Shin'Onsen, Hyogo)



Spreading of the Sea of Japan
About 17 million to 15 million years ago was a period when the Sea of Japan was expanding rapidly.



Tateiwa Rock
(Kyotango, Kyoto)
Taiza Kaigan
(Kyotango, Kyoto)


15 million years ago
from 17 million years



After the Spreading of the Sea of Japan
About 3 million years ago when the expansion of the Sea of Japan was almost over, the eruptions that formed the rhyolites began. At the Ui Rhyolites, you can see the beautiful spiral flow pattern characteristic of rhyolite.
Yoroinosode, which at a height of 65m is one of the best views in San'in Kaigan, was also formed in this period. The sheet of Mio Oshima at Tajima Mihonoura, a scenic spot and natural monument, also originated from the same magma.



Yoroinosode(Kami,Hyogo)
Ui Rhyolites
(Toyooka, Hyogo)

about 3 million
years ago


San'in Kaigan Geopark Promotion Council
    376-14 Nakakage, Toyooka City,
Hyogo Prefecture, Japan
TEL:+81-796-26-3783 FAX:+81-796-26-3785
E-mail:geopark@pref.hyogo.lg.jp


Copyright@2008 San'in Kaigan Geopark Promotion Council. All rights reserved