English: Rishiri Island is a volcanic island in the Sea of Japan off the northwestern tip of Hokkaido. Rishiri volcano started erupting less than 200,000 years ago, building a stratovolcano and lava domes. Eruptions from the summit vents ceased about 37,000 years ago and since then, the only activity has been sporadic eruptions from flank vents, forming scoria cones and maars along a 15-km-long NW-SE rift zone extending to the SE coast. These flank eruptions last occurred about 8,500 years ago and were dominantly basaltic, but occasionally included more silica-rich magma including rhyolite. Large lava flows form most of the northern and western coast. When the lava flowed into the ocean, it cooled and formed unusual rock formations which can be viewed at Senhoshi-Misaki Park on the south coast where they protect many tide pools. The white stains on the rocks are sea gull excrement as the area is home to colonies of black-tailed gulls seen perching in the distance.