Mt. Mashu Profile
Mt. Mashu is located on the eastern edge of Lake Mashu, one of the world’s clearest lakes. From the mountain’s 857-meter summit, you can view this spectacular caldera lake and the surrounding volcanic terrain, including Mt. Shari, a 1,547-meter peak located halfway between Lake Mashu and Shiretoko National Park. A fork in the trail—located at the beginning of the ascent to Mt. Mashu’s summit—leads east to Mt. Nishibetsu. Determined hikers can scale both mountains in one trek.
Mt. Mashu Trekking Trail
The trailhead begins at Lake Mashu Observation Deck No. 1 and follows the ridge of the Mashu Caldera. There are viewing points along the route with uninterrupted views of the lake, and in summer, alpine flowers bloom in meadows not far from the trailhead. Just past the junction that branches off to Mt. Nishibetsu, a large explosion crater comes into view. Experienced hikers will find this trail relatively easy, however the final section requires a good level of fitness due to the steep incline.
Lake Mashu
Lake Mashu is a caldera lake formed by the buildup of rainwater and snowmelt inside the hollow crater, which was created by a massive volcanic eruption. The lake is one of the world’s most transparent bodies of water; its deep, distinctive blue color is known as “Mashu blue.” No rivers feed into or flow out from the lake, and steep caldera walls surround it on all sides.