BackgroundMacauley Island is a remnant of the rim of a large submarine caldera centered 8 km to the NW. The 3-km-wide island consists of a low, gently sloping surface of rhyolitic pumice from the caldera-forming eruption truncated by steep cliffs formed of underlying basaltic lava flows. The pre-caldera Macauley volcano consisted of two generations of shield volcanoes separated by a period of growth of a pyroclastic cone. Eruption of the voluminous Sandy Bay Tuff about 6300 years ago truncated the NW side of the Annexation shield volcano and formed a 12-km-wide, 1.1-km deep caldera during one of the largest eruptions identified in the SW Pacific. Following formation of the caldera and substantial marine erosion, a partly submarine and partly subaerial eruption centered about 2 km north of present-day Macauley Island produced basaltic scoriae and lava flows. A reported possible eruption from "Brimstone Island," 45 km west of Macauley at a location with a depth of about 2000 m and SW of Giggenbach submarine volcano, is likely a location error and could refer to an eruption from the submarine flank of Macauley caldera (Lloyd et al., 1996).
Smithsonian / GVP volcano information
See also: Sentinel hub | Landsat 8