Mt Shiga

Mt. Shiga (Japanese: 志賀山) rises quietly within the highlands of Shiga Kōgen, a mountain shaped by the volcanic forces that built this entire plateau. It is part of the Shiga volcanic complex and its landscape still reflects that origin with rugged lava flows, crater rims softened by time and a network of lakes and marshes formed when ancient eruptions dammed valleys and reshaped the terrain.

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One of the pleasures of Mt Shiga is how naturally it fits into a loop hike with Mt Ura‑Shiga (裏志賀山) that overlooks a network of pools and marshland. The trails weave through forests, wetlands and old volcanic ground, linking viewpoints, ponds and ridgelines. Shiga Kōgen is rich in paths: routes that circle the famous Shijūhachi‑ike wetlands, trails that pass by Ōnuma Pond, and longer ridge courses that connect Shiga with the surrounding peaks of the national park. Many of these paths follow the contours of the ancient caldera, where volcanic activity created uneven terrain, steep escarpments and clusters of crater lakes.

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The geology here is unusually expressive. Shiga Kōgen’s foundation includes ancient seafloor volcanic deposits overlain by younger lava flows and pyroclastic material from the Shiga and Kusatsu‑Shirane volcanic systems. In places, you can still see rare spiral lava formations and columnar joints, remnants of eruptions that cooled in distinctive patterns. The region’s rugged cliffs, such as the well‑known Makuiwa, were carved by erosion acting on these volcanic layers.

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The climate is alpine, with long winters and heavy snowfall that shape both the terrain and the ecology. When I hiked there in early summer there was still a lot of remianing snow that was difficult to negotiate. The snowmelt feeds the marshlands and summers are cool and short, bringing a burst of high‑altitude flora and wildlife.

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(All information here is based on personal observations and experiences. Check official sources before planning or starting any hikes.)