Recent monitoring of White Island suggests a slight increase in volcanic unrest, GNS Science says.
GNS scientists measured an increase of carbon dioxide in the gas emitted at the largest accessible steam vent on October 1.
A statement from GNS said these subtle changes also coincided with the presence of volcanic tremor and more elevated amounts of sulphur dioxide gas being emitted from the volcano. This indicated that unrest at White Island might have increased slightly in recent weeks.
GNS geochemists sampled the largest accessible steam vent on October 1. This sampling indicated a small increase in the temperature to 170C and an increase in the amount of carbon dioxide gas. These are consistent with the other gas measurements made at White Island.
Volcanic tremor is a common type of volcanic earthquake activity recorded on the island. Since October 8, this has been increasing in strength and become "banded".
Banded tremor is common at White Island and many active volcanoes worldwide. It has been recorded during increasing unrest and a variety of eruptive periods in the past.
During visits to the island in October, GeoNet staff also sampled and measured the lake temperature (54C) and it remains similar to other recent measurements. However, the lake level has risen about 2 meters since June. Since the lake re-established in late 2013 we have measured a rise of about 6m.
The Volcanic Alert Level remains at Level 1 (minor volcanic unrest). The present changes being observed are common for the island.
Activity may continue to increase or die away. 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 Science is continuing to closely monitor the activity at White Island (and other New Zealand volcanoes) through the GeoNet project.