samedi, avril 13, 2013
GNS reported that "the temperature of Crater Lake has started to rise and has now reached 30°C. It has been accompanied by some minor volcanic tremor. The chemistry data from our last sampling trip confirms the decline of temperature in the deep geothermal system. ... [details]
mardi, mars 12, 2013
The latest lake water temperatures readings and seismic recordings showed no particular signs of unrest in recent weaks and the volcanic alert status level has been reduced back to normal=green. [details]
Ruhapehu volcanRuapehu is one of New Zealand's most active volcanoes and forms the highest peak of the North Island. The andesitic stratovolcano has an age of around 200,000 years and contains a large summit crater containing a lake. Eruptions from the vent inside the lake often cause the lake to drain and form dangerous lahars.
Introduction:Ruapehu is a complex volcanic edifice constructed over several cycles and has a NNE-SSW elongated shape. The cone is surrounded by a large plain formed by debris from flank collapse and lahar deposits.
A series of very explosive (Plinian) eruptions occurred at Ruapehu between about 22,600 and 10,000 years ago. Since then, only one vent has probably been active, Crater Lake in the summit region. Activity in historic time consisted of mild explosive phreatic and phreatomagmatic eruptions often accompanied by lahars threatening the popular ski area on the volcano as well as structures in the surrounding valleys.
An eruption on 24th December 1953 caused a catastrophic lahar that destroyed a rail bridge 42 km from the volcano, just as the Wellington-Auckland passenger train was crossing and fell into the valley, causing 151 fatalities.
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