In early March 2024, Geonet first observed an uncommon style of small earthquakes at Ruapehu. Subsequent re-examination of seismic data has revealed those earthquakes commenced at least as early as mid-February.

The earthquakes are small and were initially difficult to identify without careful examination of the data as they are uncommon at Ruapehu and only the larger examples are detected by Geonet’s automatic systems. Over the last month, they have seen a maximum of six of these earthquakes a day, and on many days none at all.

Each earthquake consists of up to about 10 minutes of ground shaking, and is composed of a number of similar sub-events. While Geonet are able to determine a location for some of the larger examples, the small size and style of the activity means locations, especially depth, are quite uncertain. However, as they are recorded only by monitoring stations on the upper part of the volcano, Geonet speculate that they originate near the summit area of the volcano within a few kilometres’ depth beneath the surface.

As the earthquakes do not typically last more than 10 minutes, they do not constitute volcanic tremor, and that remains low. The earthquakes are also quite different in appearance from volcanic tremor traditionally seen at Ruapehu.

While the earthquakes represent something new at Ruapehu, and Geonet are working on understanding the details of the processes driving them, they are not thought to pose any concerns for eruptive activity. Other monitored parameters have shown no recent changes. The temperature of Te Wai ā-moe (Crater Lake) is now relatively stable at about 24 ºC, recent observations of the lake recognised nothing unusual, gas emissions from Ruapehu remain moderate, and volcanic tremor is low.

History of modern eruptions

1969 and 1975 eruptions

The eruption in 1969 occurred in the early hours of 22 June. It was a moderate phreatic eruption, which blasted rocks up to 1 km northwest of the crater and sent lahars down several valleys. The Whakapapa skifield was left covered in mud. This was the largest eruption since 1945

1995–1996

The first significant eruption took place at 8:05 a.m. on 18 September 1995, raining tephra onto the summit region and sending lahars down the mountain. On 23 September, an even larger eruption blasted rocks up to 1.5 km from the crater, sent lahars down three valleys, and generated an eruption column 12 km high.

2006 and 2007 

Ruapehu erupted at 10:24 p.m. on 4 October 2006. The small eruption was marked by a magnitude 2.9 volcanic earthquake and sent waves 4–5 m (16 ft) tall crashing into the wall of the crater. No ash was erupted into the atmosphere, and the eruption is presumed to have occurred entirely underwater.