The underground of Ogata Village is the same stratum as the Oga Peninsula
The rock layers that make up the Oga Peninsula are as old as 90 million years, with the oldest datingback to that period.
These layers can be divided into two main types: one consists of volcanic ashand materials that accumulated on land before about 20 million years ago, while the other is made up of sediments like sand and mud that settled on the sea floor after that time.
Until around 20 million years ago, the Oga area was land, but it became submerged after that.
The same geological layers found in Oga also extend into Ogata Village, showing that the geological history of the Oga Peninsula is shared with Ogata.
However, in Ogata, these layers are not visible at the surface.
This is because they are covered by more recent deposits, formed around 10,000 years ago, when Lake Hachirogata was created.
These newer layers are typically found about 100 meters below the surface.
The fact that the older layers of Oga are buried deep underground in Ogata suggests that the Oga Peninsula has been uplifted, while the Ogata area has subsided.
This subsidence allowed water to accumulate in the region, creating the conditions for new layers to continue forming at the bottom of the lake.
In the northeastern part of Ogata Village (on the mainland side), the same geological layers that are found in Oga can be seen at the surface.
