Mashu Lake and Mount Io: Natural Wonders of Eastern Hokkaido

Located in Akan-Mashu National Park in Hokkaido, Mashu Lake and Mount Io are iconic natural attractions of Eastern Hokkaido, showcasing the unique charm of volcanic landscapes and lake ecosystems. Mashu Lake: The Sapphire Lake Mashu Lake is a caldera lake formed approximately 7,000 years ago by volcanic eruptions. It has a circumference of about 20 kilometers and a maximum depth of 212 meters (Reference: Japan Ministry of the Environment, "Overview of Akan-Mashu National Park"). With no rivers flowing in or out, the lake boasts exceptional water transparency, once measured at 41.6 meters in 1931, a world record at the time. Its crystal-clear surface reflects the sky, creating the enchanting "Mashu Blue" hue. The lake features two main observation points: the First and Third Observation Decks. The First Observation Deck is well-equipped with facilities, including the Kamui Terrace, offering rest areas and the signature "Mashu Blue" ice cream. The Third Observation Deck provides a panoramic view, including Kamui Island at the center of the lake. Due to frequent mist and fog, clear views of the lake are considered a symbol of good luck. Mount Io: The Thrill of an Active Volcano Mount Io (Atosanupuri), located between Mashu Lake and Lake Kussharo, stands at an elevation of 508 meters and is an active volcano formed approximately 1,700 years ago (Reference: Hokkaido Tourism Organization). The slopes are dotted with fumaroles emitting white sulfur-rich steam accompanied by a strong smell and "popping" sounds, offering a visceral sense of Earth's pulse. Visitors can observe sulfur crystals up close along the rugged terrain but should heed safety warnings and barriers. At the base of the mountain, the "MOKMOK Space" offers treats like hot spring eggs and sulfur-flavored ice cream, adding a fun twist to the visit. Travel Tips It is recommended to drive or join a private tour. Parking at Mount Io costs 500 yen and can be shared with Mashu Lake's First Observation Deck. In summer, visitors can enjoy the blooming Ezo azaleas, while in winter, Mount Io is closed (late November to early April). Mashu Lake and Mount Io are about a 20-minute drive apart, making them ideal for a one-day trip. The tranquility of Mashu Lake and the dynamic energy of Mount Io create a unique natural contrast in Eastern Hokkaido, offering travelers a profound experience of Earth's vitality.