The surface of Santorini is covered with the famous pumice stone originated from the eruption that destroyed the Minoan civilization. Exposure of about 150 feet (50 m) of Minoan tephra. The tephra consists of pumice (Light-colored, frothy volcanic rock, usually of dacite or rhyolite composition, formed by the expansion of gas in erupting lava. Commonly seen as lumps or fragments of pea-size and larger, but can also occur abundantly as ash-sized particles), pyroclastic surge, and pyroclastic flow deposits. Photography copyrighted by Robert Decker.