Geohistory - Terrain
This strangely shaped rock looks like a lizard climbing up the face of a cliff. Approximately 26 m tall, Tokage-iwa (Lizard Rock) is made up of trachyte lava that flowed into pyroclastic rock and solidified (intrusive rock) around 5.5 million years ago. This trachyte rock is harder than the surrounding pyroclastic rock, and therefore less prone to weathering; because of this, it is thought to have remained behind longer, resembling the shape of a lizard.
Tokage-iwa is unusual not only in its appearance, but also in its rock composition. Among the trachyte rock found in the Oki Islands, it has been found to have a particularly high percentage of alkaline elements such as sodium and potassium. What is notable about this is that rocks rich in alkaline elements are characteristic of continental rocks. They are rarely found in the Japanese archipelago, and therefore may provide clues to the geological peculiarities of the Oki Islands.
