GeoNet reported that minor unrest continued at Ruapehu and the crater lake remained cool. The temperature of the crater lake water decreased from 31 to 11 degrees Celsius during March-August and remained cool through 8 October, decreasing further to 8 degrees, the lowest temperature recorded since 1970. Sulfur dioxide emissions were at low-to-moderate levels. The reduced temperature and sulfur dioxide emissions suggested partial sealing of the vent; areas of upwelling on the lake’s surface and sulfur slicks were visible on 30 September. Volcanic tremor levels remained low during 2024. The Volcanic Alert Level remained at 1 (on a scale from 0-5) and the Aviation Color Code remained at Green (the lowest level on a four-color scale).

Geological Summary. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the NW-flank Murimoto debris-avalanche deposit. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. The broad summait area and flank contain at least six vents active during the Holocene. Frequent mild-to-moderate explosive eruptions have been recorded from the Te Wai a-Moe (Crater Lake) vent, and tephra characteristics suggest that the crater lake may have formed as recently as 3,000 years ago. Lahars resulting from phreatic eruptions at the summit crater lake are a hazard to a ski area on the upper flanks and lower river valleys.

Source: GeoNet