Description: From Miller and others (1998): "The eastern volcanic center, to which all recent Yunaska volcanism has been attributed, has been described by Nicolaysen and others (1992) and Lamb and others (1992) in preliminary reports as a large shield volcano topped by two overlapping calderas. No age has been reported for caldera formation but the fresh morphology of the younger caldera and the non-glaciated nature of the associated pyroclastic rocks suggests it at least is Holocene in age. The older of the two calderas (caldera CI, Lamb and others, 1992) has a diameter of 10-13 km, the younger (caldera CII) about 3 km. Low ridges and peaks along the northern and eastern shores of the island define the postulated caldera (see physiographic descriptions in Sekora, 1973)."