On 30 March the IGNS reported that a moderate-sized hydrothermal explosion occurred in the Alum Lakes area, Wairakei, knocking over trees and destroying vegetation near the crater. Water levels at several of the Alum Lakes had dropped several weeks before the explosion.

Geological Summary. The 16 x 25 km area defined as the Maroa Volcanic Centre formed sometime after 230,000 years ago (230 ka) in the NE corner of the 30 x 40 km Whakamaru caldera, which is the largest of the Taupo Volcanic Zone. The Whakamaru caldera partially overlaps with the Taupo caldera on the south and was formed during the eruption of the Whakamaru Group ignimbrites between about 340 and 330 ka. The Maroa area was subsequently filled by at least 70 rhyolitic lava domes or flows, mostly erupted along a SW-NE trend. Lesser amounts of basalt were also erupted. The latest dated magmatic eruption took place about 14 ka, when the rhyolitic Puketarata tuff ring and lava domes were formed (Brooker et al., 1993). The Orakeikorako, Ngatamariki, Rotokaua, and Wairakei hydrothermal areas are located within or adjacent to the Whakamaru caldera. Large hydrothermal eruptions have occurred at the Orakeikorako thermal area during the Holocene, the latest immediately prior to the Taupo eruption about 1,800 years ago.

Source: GeoNet