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.
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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)