Activity at New Zealand's White Island remains quiet after a small earthquake swarm nearby. While there are no apparent changes in activity after the swarm, scientists noted the reappearance of a Crater Lake on the floor of the Active Crater area.
GeoNet monitoring teams visited White Island on March 14, 2018 and found it quiet. The monitoring team undertook a ground deformation survey, measured fumarole and vent temperatures, sampled springs and the Crater Lake. "These activities are part of the routine monitoring undertaken at White Island every 3 months," volcanologist Brad Scott said. These visits complement the seismic, acoustic, GNSS, web camera and gas data that are collected continuously, he added.
The most significant change they noticed is the reappearance of a Crater Lake on the floor of the Active Crater area. This appears to be a response to the rainfall from the recent cyclones. The lake temperature is relatively cool at 27 ºC (80.6 ºF).
Newly formed Crater Lake at White Island, New Zealand. Credit: GeoNet
Temperatures of both the Dome vent in the active crater and Fumarole 0 on the Main Crater floor continue to decline, Scott said.
The Dome vent is now 128 ºC (262.4 ºF), down from 157 ºC (314.6 ºF) in December 2017. While Fumarole 0 is down from 144 to 138 ºC (291.2 to 280.4 ºF). Spring and stream flows have also declined, which is consistent with the lower water level in the Crater Lake or following periods with no lake present. The ground deformation survey also shows subsidence towards the Active Crater of 2 - 5 mm (0.08 - 0.20 inches) per month.
The seismic activity has been low in recent months, however, there was a sequence of small earthquakes near the island over the weekend. The largest earthquake was M3.3 at 11:37 am (local time) on Saturday, March 17. GeoNet detected no changes at the island related to these earthquakes.
White Island is always capable of a new eruption at any time, often without any useful warning, Scott said, adding that they continue monitoring the volcano for possible renewed activity.
The Volcanic Alert Level remains at Level 1 and the Aviation Colour code remains Green.
Uninhabited 2 x 2.4 km (1.2 x 1.5 miles) White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km (10 x 11.2 miles) submarine volcano in the Bay of Plenty about 50 km (31 miles) offshore of North Island. The 321-m-high (1 053 feet) island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE because the shoreline corresponds to the level of several notches in the SE crater wall. Volkner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km (3.1 miles) NNE of White Island.
Intermittent moderate phreatomagmatic and strombolian eruptions have occurred at White Island throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. The collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. (GVP)
Featured image: Newly formed Crater Lake at White Island, New Zealand. Credit: GeoNet