Geological Composition of Dōgo

The rugged western cliffs of Dogo Island are made of rhyolite, a volcanic rock that looks white when weathered but reveals patterns of lavender, gray, and black on a freshly split surface. Because rhyolite lava is extremely viscous, it hardened in intricate layered formations along the coast, the result of different minerals solidifying and sinking at different rates as it cooled. Large spherical cavities in the rock formed from spherulites, crystalline structures typical in silica-rich stone. That same high silica content also created deposits of obsidian, visible in the lava flows. The coast here reads like an open geology textbook.