Over the last couple of weeks, GNS scientists have observed a fall of 2 meters (6.5 feet) in the water level of the Crater Lake at White Island (Whakaari), New Zealand. However, they have not noted any changes in other monitored parameters like the amount of volcanic gas being emitted, fumarole temperatures and the presence of volcanic tremor or earthquakes.
GNS volcanologist Brad Scott visited the volcano last week and confirmed the lake level has dropped 2 m in the last two weeks. The lake is now at about the same level it was in 2014. The drop in water level of the Crater Lake has revealed several islands or crater outlines and the lake temperature has increased 2 ºC (35.6 ºF), from 56 to 58 ºC (132.8 to 136.5 ºF) since February 2016.
White Island volcano, New Zealand - April 2016. Credit: GeoNet
There has been a small decrease in the temperature of the hottest fumarole, from 169 to 161 ºC (336.2 to 321.8 ºF) since February. The SO2 gas output has ranged between 90 and 480 tons per day (1.0 to 5.5 kg per second) of gas during the last five weeks. These are typical values for White Island, GNS said.
The level of volcanic tremor continues to vary but remains below those observed in 2012 when unrest was stronger and small eruptions occurred.
The Volcanic Alert Level remains at Level 1 (minor volcanic unrest).
"The changes we are seeing presently are consistent with minor volcanic unrest. Typical volcanic unrest hazards like hot ground and gas remain. A range of activity can occur under these conditions with little or no useful warning," GNS volcanologist Brad Scott concluded in his April 27th update.
The last eruption of this volcano took place in 2012 and 13.
The eruption of White Island volcano on August 20, 2013. Credit: GeoNet
Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The 321-m-high 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 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: White Island, New Zealand - April 2016. Credit: GeoNet