Monthly Archives: September 2012

Alert Level 1, Status Green and the Big Picture

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Mt Ruapehu’s status is now green which means the volcano is in normal, non-eruptive state.

To see why New Zealand is volcanically active let’s take a look at the big picture.

To the left of the picture is the Australian Plate and to the right is the Pacific Plate.  The Pacific Plate comprises very heavy oceanic crust; it wants to sink.  And it is in fact subducting beneath the lighter continental Australian Plate, particularly in the north.  The south is a slightly different story because all plates are not created equal and actually comprise both types of plate.  But we aren’t interested in the South Island – as interesting as it is with the fabulous Southern Alps.

The triangles note the movement direction of the tectonic plate.  To the left of the plate boundary you see a double line parallel with the boundary extending from the Ruapehu complex right up into the Pacific.  This is the Kermadec Trench which morphs into the Tonga Trench.  As the Pacific Plate dips into the mantle beneath the Australian Plate it catches the bottom of that plate and pulls on it, fracturing it.  Thus this part of the crust is being torn apart.  The whole land area that is being ripped apart is referred to as the Taupo Volcanic Zone (TVZ).  The rates of pull are different, being 2-3mm per year at the Ruapehu end and about 5mm per year at the White Island end.

You can identify the Ruapehu complex as the green spot at the bottom of the rift.

Just note how big the continental area around New Zealand is.  The light piece coming from the right in the South Island is the Chatham Rise.

Alert Level 1, Colour Satus Yellow

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It’s five weeks today since Mt Tongariro reminded us of its presence with an eruption. At present it is still on Alert Level 1 which signifies signs of volcano unrest and a departure from typical background surface activity. Its colour level is yellow which means that volcanic activity has decreased significantly but continues to be monitored for possible renewed unrest.

Take a look at http://www.geonet.org.nz for the latest. Also click on the cameras to get a sequence of images. Today dawn is about 6 am and it’s bright and cloudy, with a few specks of rain on the Tongariro camera.

Imagine Lana and Paul holed up in a hut on the side of Mt Ruapehu, volcanic rocks raining down. Brrr, dangerous stuff.  Smashwords ISBN 978-1-47 6-25231-5, Amazon ISBN 978-0-473-22189-8