Based on satellite data, the Wellington VAAC reported that an eruption at Tinakula began around 0620 on 21 October, producing a sulfur dioxide signature, and an ash plume that rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted N. Another eruption at 1040 generated an ash plume that rose significantly higher that the first, to an altitude of 10.7 (35,000 ft) a.s.l. and drifted SE. Later that day ash plumes rose to 6.1 km (20,000 ft) a.s.l. Ash emissions continued through at least 24 October, rising to altitudes of 3-3.7 (10,000-12,000 ft) a.s.l. and drifting E and W on 22 October, 2.4 km (8,000 ft) a.s.l. and drifting S and SE on 23 October, and 1.8 km (6,000 ft) a.s.l. with a SW drift on 24 October. A news article from 24 October stated that water supplies in the Reef Islands had been contaminated with ashfall, and that ashfall was also reported in Fenualoa, and likely in Nupani.

Geological Summary. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. It has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The Mendana cone is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Recorded eruptions have frequently originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

Sources: Wellington Volcanic Ash Advisory Center (VAAC), Radio New Zealand