Twister Sisters, Prime, 2030 tonight.

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GraemeWi
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Unread post by GraemeWi »

NZ Thunderstorm Soc wrote:I reckon the area around Hanmer could split and fire up?
Thats a South Island perpective?

JohnGaul
NZES
Nah - your safe in the South Island - all the hot springs there are 'low temperature' springs associated with water being heated by soaking through the rocks down to about 5km and being heated by the temperature down there - comes back to the surface via faults. No volcanics in the South Island.

Cheers,

G
NZ Thunderstorm Soc
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Unread post by NZ Thunderstorm Soc »

GraemeWi wrote: No volcanics in the South Island.

Cheers,

G

Don't be a spoil sport Graeme ;)

JG
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spike_01
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Unread post by spike_01 »

Lake Taupo... Mmmmmm Volcanic Crater.... :P :P
C-Nimbus
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Unread post by C-Nimbus »

Just thought i'd shed some light on this seeing as I am a geologist by training.

The Auckland volcanic region is made up of intra-crustal basalt melt lavas that are not deep seeted in the crust, so a 9km depth epicentre could be hinting at possible magmatic movements, or it could simply be a gas release from an already molten magma chamber at depth, this is more likely. Prior to volcanogenisis there would be considerable land deformation and considerable changes in water chemistry that would hint at something happening. Therefore the 'burp' idea is the best one.

Just to clear up too, White Island is not related to Auckland volcanic region in any way. White Island is the northernmost volcanic vent for TVZ (Taupo Volanic zone) which is formed in a back arc arrangment relative to the subduction trench on the eastern side of NZ, you can pretty much draw a straight line between Taupo and white island, and this runs approx. parrallel to the subduction zone. These volcanoes are formed from a melting subduction slab as it ascends into the asthenosphere (molten) as they melt, globules of magma make it up to the surface and some erupt in the form of andesitic/dacitic strato volcanoes or rhyolitic calderas based on the chemistry of the lava.

They say that white island is like a vent for TVZ, which is believable, and as one person has said on here the actual crater is below sea level which is of concern. This can lead to whats known as a Surteseyan (sp?) eruption (mixing of cold water and hot lava) if the crater walls erode.
Scary stuff, esp if you live in the bay of plenty.

Hazards will come from Auckland, there is no doubt about that, its just a time thing. It is however likely to next form a dome between Rangitoto (800 years BP) and great barrier based on the migration of the basalt field.

Our biggest hazard tho is not from basaltics, but from rhyolitic/pyroclastic sources such as TVZ and RVZ (Rotorua volcanics). This style of volcanics is what puts NZ into third world status in about a day, and evidence of this can be seen in the huge Ongatiti welded Ignimbrite (Hinuera Stone) deposit which covers a large portion of the south waikato. This is from the mangakino caldera, which would make the 1.8ka taupo eruption look like a fire cracker..

crazy stuff!
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