Mt. Kashiwagi, Yurijima Island, and Tateiwa Rock are a reddish color, made of a volcanic rock called rhyolite. This rock formed from a viscous (sticky) lava that erupted from a volcano around 9 million years ago.

From the southern tip of Tobishima Island to a spot on its southwest coast called “Sai-no-kawara,” there is a walking trail where visitors can see and touch rocks with a beautiful flow structure, which formed when the lava flowed and solidified. Tobishima Island has particularly strong winds and waves in winter, causing erosion that has created various rock formations along the coast over time, which can be seen from the walking trail. You can also find evidence of Tobishima Island’s repeated uplifting in the uplifted marine terraces and potholes.

Mt. Kashiwagi is designated by Sakata City as a Natural Monument as a place where peregrine falcons (Falco peregrinus) nest and the Tobishima daylily (Hemerocallis middendorffii var. exaltata) and warm-climate shrub Japanese garden juniper (Juniperus procumbens) grow wild. On the mountain’s summit, a concrete pillar remains where Japanese physicist Terada Torahiko attempted to confirm his theory of continental drift about 100 years ago.