Adagdak

Geological summary

Mount Adagdak, at the NE tip of Adak Island, lies across Andrew Lagoon from Mount Moffett volcano and ~15 km NNE of the town of Adak. It consists of a small stratovolcano capping an older shield volcano exposed on the southern side of the complex. An andesitic lava dome fills the summit crater. A late-stage basaltic lava dome was constructed on the SE flank, and a phreatic vent is located on the W flank of the shield volcano. The most recent eruptions are thought to be Holocene (Marsh, in Wood and Kienle 1990) or Pleistocene (Motyka et al. 1993, Nye et al. 1998). Three stages of volcanism were mapped by Bratten, the youngest of which was a lava dome dated at about 210,000 years (AVO, 2005-). The older Andrew Bay volcano, located north of Andrew Lagoon between Adagdak and Moffett volcanoes, is preserved only in erosional remnants. Andrew Bay Hot Springs lie along the coast west of Mount Adagdak.