James Healy Seamount

Healy submarine volcano lies along the South Kermadec Ridge and consists of an elongated edifice with a 3 x 4 km wide caldera at the NE end whose rim reaches to 1,150 m below sea level. A smaller caldera lies to the SW, and a cone, Cotton volcano, rises to 980 below sea level at the SW end of the 15-km-long complex. The flat-lying floor of the larger NE caldera lies 250-400 m below the caldera rim. Rhyodacitic pumice deposits mantle the caldera floor and walls, as well as the flanks. Active hydrothermal venting has been observed on the lower part of the southern caldera wall. The roughly 590-year-old sea-rafted Loisels Pumice deposit found in many Holocene beach sequences of North Island, New Zealand, and as far away as the Chatham Islands, 650 km east of New Zealand, is chemically and texturally similar to pumices from Healy caldera.