Re:8월 10일 영어 문서반 자료 ; 화산 폭발 관련기사2 ; Tongariro eruption: All you need to know

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Tongariro eruption: All you need to know                                3:08 PM Tuesday Aug 7, 2012

Vic Cassin sweeps ash from one of the vehicles parked on his section near Turangi, which was in the path of the ash cloud that resulted from last nights eruption of Mt Tongariro. Photo / Alan Gibson

Mt Tongariro rumbled to life for the first time in more than a century this morning, spewing a giant ash cloud as far as Napier.

Dr Thomas Wilson, a disaster management lecturer at Canterbury University, explains all you need to know about the eruption, its aftermath and what the future may hold.

What type of eruption was it?

There are three main types of eruptions you can get in an explosive event. There's what we call a phreatic eruption, or steam-driven eruption. This is where water has been superheated by magma under the volcano, but it's only the water that erupts in an explosive manner. Basically the hydrothermal system underneath the volcano erupts, and this is what seems to have occurred on Tongariro.

Another type is a phreatomagmatic eruption, where water has come into contact with magma and caused the magma to fragment in an explosive eruption.

Then there's a magmatic eruption, where there's no water interacting, and it's just the magma erupting itself.

Maori descriptions of the event spoke of "bright red flame through the smoke that would burst and fall like snow".

The mountain again let loose in November 1892, spewing steam, mud and boulders 2000-3000 feet into the air.

A journalist for the Auckland Star reported a "heavy booming" from Tongariro on February 9, 1892.

"I had a glimpse of the mountain for a few minutes to-day; it was sending up steam and smoke to a tremendous height."

The 1897 eruption dumped 50 millimetres of ash on the Desert Road and ash drifted as far as Napier.

GeoNet says Tongariro typically experiences two quakes of a magnitude 2.5 or less each year but there had been more than 20 since July 13.

There are six alert levels of volcanic action, increasing in seriousness from zero to five. Alert level one indicates "signs of volcano unrest".

For the alert level to be lifted to two - "minor eruptive activity" - there would need to be an eruption.                                - Herald Online