Eruption at Tongariro

A small ash eruption occurred at Mt. Tongariro in the central North Island this afternoon.

Wednesday, 21 November 2012

An ash eruption occurred at the upper Te Maari crater on the slopes of Mt. Tongariro at 1:25 this afternoon. Today’s event was smaller than the eruption that occurred at the same location on August 6th. Also unlike the August event, today’s eruption occurred without warning.

This afternoon’s eruption lasted for about five minutes with local earthquake activity continuing for about a quarter of an hour.

The West Tongariro seismic drum shows the eruption occurring about six-and-a-half hours before this snapshot was taken. The red trace shows the initial force of the eruption followed by five minutes of shaking while the ash eruption occurred. Over the following quarter hour, minor tremor was recorded.

GeoNet has released a time-lapse video of the eruption as it occurred at Mt. Tongariro. The ash eruption occurs 38 seconds after the video starts playing. This is a time-lapse movie, compiled from images taken at 1 second intervals.

During the eruption, ash rose to heights of three to four kilometres, and the aviation alert status of the volcano was raised to red. The plume was clearly seen from Taupo and a light dusting of ash fell across State Highway 46 and towards Turangi. Today’s eruption did not produce a noticeable ejection of rock or other debris as occurred during the August event.

Activity subsided after the twenty-minute event, but steam continues to be emitted from Te Maari vents.

When Tongariro became active again in August this year, vulcanologists saw sufficient signs in the lead-up to the eruption to issue a warning. Today’s eruption, though smaller, occurred without warning such as increased volcanic tremor. Until this year, the volcano had been quiescent since the 19th century. Today’s event indicates that the volcano’s activity over the coming months could follow eruptive activity recorded in the late 1890s. If so, an eruption of similar size could occur at any time over the coming weeks but, from the two latest events, activity is not expected to escalate in size.

The aviation alert for the volcano has now been reduced to orange (volcanic eruption is underway with no, or minor, ash emission). The Volcanic Alert Status for Tongariro remains at 2 (minor eruptive activity).

[Compiled from data provided by the GeoNet project and its sponsors EQC, GNS Science and FRST.]

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