Source: XINHUA | 2013-1-22 | ONLINE EDITION
WELLINGTON, Jan. 22 (Xinhua) -- New Zealand scientists said Tuesday they are concerned about growing "volcanic unrest" at an active volcano off the country's North Island.
Volcanologist Brad Scott, of the government's Institute of Geological and Nuclear Sciences (GNS Science), visited White Island on Monday and found that hydrothermal activity in a small " hot lake" had increased.
The most common activity was "doming-up" of the lake surface by steam and gas, bringing large amounts of sediment to the surface, often with vivid white steam and gas "flashing" from around the base, with stronger events every so often.
This activity had been increasing since late last year and was now semi-continuous, Scott said in a statement from GNS Science.
"The hydrothermal activity is some of the most vigorous I have seen at White Island for many years. This type of activity usually leads to stronger volcanic activity and is a significant concern," said Scott.
The lava dome that was first observed in late November had not changed since the last observations on Jan. 1.
Seismicity continued to show elevated levels of volcanic tremor, which was likely generated by the processes driving the vigorous hydrothermal activity in the lake.
The state of unrest at White Island was increasing and past activity indicated that future eruptions could occur with little or no warning, he said.
He also warned that the increased level of unrest could pose a hazard to visitors to the island, which is a popular tourist attraction lying about 50 kilometers off the east of the North Island.
Past activity indicated that eruptions could occur with little or no warning, he said.
White Island last erupted in August last year, sending up an ash plume 200 to 300 meters in the air, in its first eruption since 2001.
Volcanologists have been warning that New Zealand could be entering a period of increased volcanic activity.
In November last year, GNS Science warned that the central North Island mountain of Ruapehu was showing signs of an imminent eruption, and in August Mount Tongariro, also in the central North Island, erupted throwing out small amounts of ash in its first eruption since 1897.