On 20 April GeoNet reported that it had been three weeks since anomalous seismicity at Tongariro's Ngauruhoe cone had been detected. In addition, no anomalous ground temperatures or unusual levels of gas emissions were detected at the summit during fieldwork, indicating that the minor unrest had ceased. The Volcanic Alert Level was lowered to 0 (on a scale of 0-5).

Geological Summary. Tongariro is a large volcanic massif, located immediately NE of Ruapehu volcano, that is composed of more than a dozen composite cones constructed over a period of 275,000 years. Vents along a NE-trending zone extending from Saddle Cone (below Ruapehu) to Te Maari crater (including vents at the present-day location of Ngauruhoe) were active during several hundred years around 10,000 years ago, producing the largest known eruptions at the Tongariro complex during the Holocene. North Crater stratovolcano is truncated by a broad, shallow crater filled by a solidified lava lake that is cut on the NW side by a small explosion crater. The youngest cone, Ngauruhoe, is also the highest peak.

Source: GeoNet