Participants were given the lecture by Mr. Yasumitsu Kanie of a curator of the Yokosuka City Museum during the morning in the classroom, and they observed and turned around the strata in Mabori and Kannonzaki by fieldwork in the afternoon.

I am living in Mabori seaside and I also have the relation which is carrying out the earth science volunteer of the Yokosuka City Museum, so I jointed.

The strata in Mabori & Kannonzaki are based on the mudstone(Zushi stratum) about 5 million years ago and the tuff(Ikego stratum) about 4 million years ago deposited on the place of 2000 meter of the seabeds.
Although the base upheaved ashore, after that the base erosioned and the hollow place sank in the sea again.

The fossils of shellfish are discovered from the strata (Yokosuka strata: Otsu stratum + Hashirimizu stratum) containing sand and stones which were deposited about 140 thousand years ago, and they are proving that it was the shallow sea.
After that, a base upheaves, became the Obaradai and was covered in the Kanto loam stratum ( - 10 thousand years ago) by the volcanic activity of Hakone and Fuji. The present sea level of Obaradai is 80 meter.

Referenc: Geology explanation and Geology structure diagram of Mabori Botanical Garden.(Japanese)

　* Yokosuka City Museum