Traces of Volcanic Activity
Since 3.5 million years up to about 20,000 years ago Lanyu has been transformed several times by volcanic eruptions.
Most of Lanyu is covered by thick piles of dark-colored vesicular volcanic rocks (geol. “cenozoic andesites”) erupted from volcanic activity associated with convergent plate boundaries and subduction zone. The Philippine plate is a small plate between the Eurasian and Pacific plates. Right at this juncture Lanyu is located as one of a chain of volcanic islands. (indigenous.pristine.net)