Minor volcanic unrest is being detected at Mt Ruapehu, although a sudden eruption remains unlikely, says GNS Science.
Volcanic gas monitoring has continued to measure low to moderate volcanic gas emissions and the crater lake, Te Wai ā-moe, continued to show a decline in lake temperature and minor water level overflow.
A volcanic alert level remained at one and the aviation colour code remained at green.
GNS Science said, based on the characteristics of unusual recent earthquakes, they were believed to be a type of activity called "spasmodic bursts".
"The occurrence of this uncommon style of small volcanic earthquakes beneath Ruapehu has significantly reduced, with just five observed since May 10.
"Each of these bursts usually consist of up to about five minutes of ground shaking. These events remain small, and therefore difficult to locate.
"Their short duration means that the earthquakes are not categorised as volcanic tremor, which remains low at Ruapehu."
GNS Science added the lake temperature was 16-17 ºC, down from a peak of 31 ºC on February 14.
The lake water level was fluctuating around overflow, likely reflecting less melt water as air temperatures fell and some rain and/or snow input during storms. The cooling of the crater lake, together with declining gas flux, was consistent with cooling of the hydrothermal system beneath the lake.
All of the recent observations were consistent with ongoing volcanic and hydrothermal processes and the overall low level of volcanic activity at Mt Ruapehu.
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