Mount Roundtop

The flat-topped, glacier-covered Roundtop is the easternmost and lowest of an E-W-trending line of volcanoes on eastern Unimak Island, 13 km SW of the village of False Pass. The snow and ice-covered edifice fills much of a 3-km-wide caldera that formed during the early Holocene. The caldera-forming eruption produced pyroclastic flows and a rhyolitic tephra layer that is widespread throughout the southwestern end of the Alaska Peninsula. A group of lava domes was constructed south of the volcano. No historical eruptions are known, but in the 1930's warm springs were found on its slopes.