An active volcano White Islands, New Zealand in the Bay of Plenty is showing signs of increased activity on August 2, 2012.
The aviation alert level for White Island has been lifted now by GNS from green to yellow alert for pilots flying over and near the Bay of Plenty region.
Its crater lake had recently started to re-fill and gases were now "vigorously streaming through it".
"Airborne gas measurements taken yesterday show that the discharge of some the sulphur gases has increased significantly. During the past few weeks, it has also been noted that there has been some minor volcanic tremor" duty volcanologist Michael Rosenberg said.
"During our late 2011 and early 2012 White Island's crater lake slowly evaporated to expose more steam vents and form two large muddy pools. However, sometime between Friday July 27 and Saturday July 28, the lake level rose quickly by about 3 m to 5 m. With renewed vigorous flow of gas and steam from the new lake can be seen from the air.
GNS says the lake has been inaccessible for many months and they have not been able to measure changes in its temperature or chemistry. Sulphur gases measured yesterday in the steam with gas plume have increased during the last three months but CO2 gas output remains at about the same level has been reported.
Since early July there has been very intermittent periods of volcanic tremor, including several hours early on Saturday July 28 and also during Monday and Tuesday of this week. Tremor is not uncommon at White Island but earlier this year it had been at a very low level.
A recent ground survey showed that the main crater floor is no longer subsiding and now looks like it may be rising slowly.
Such phenomena are usually typical activity for the White Islands, but this is the first substantial amount of changes to occur in the last few years.
The report goes on to say that the White Island is an active volcano but with recent changes in activity is suggesting that the hydrothermal system has become unstable, and as a result the risk alert has been increased.
GNS advises extra caution should be taken and GNS Science volcanologists are monitoring the activity and information will be released when ready.
The increased activity at the White Islands comes after Tongariro volcanoes recent alert risk, but both are not thought to be related.
New Zealand's most active volcano, White Island, was in a state of frequent eruption from 1976 to 2000.
Sitting 48 km offshore, White Island (Whakāri) is New Zealand’s most active cone volcano which has been built up by continuous volcanic activity over the past 150,000 years. About 70 percent of the volcano is under the sea, making this massive volcanic structure the largest in New Zealand.
A sulphur mining venture began on the island in 1885; this was stopped abruptly in 1914 when part of the crater wall collapsed and a landslide destroyed the sulphur mine and miners' village; twelve lives were lost. The remains of buildings from that era are now a tourist attraction.
Although privately owned, White Island became a private scenic reserve in 1953, and daily tours allow more than 10,000 people to visit White Island every year. GeoNet monitors volcanic activity and visits the island around 10 times a year
Source: Yahoo New Zealand, Geonet
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