Monthly Archives: June 2012

Magma and Lava of Mt Ruapehu

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Mt Ruapehu produces eruptions of high explosivity, but they are not the biggest like the eruption that produced Lake Taupo 26,500 years ago.  However, they can be larger than those that created Rangitoto Island 600 years ago in Auckland’s Hauraki Gulf.

This is due to the composition of the magma and the amount of water contained in it.  Magmas are generated from partially melted source rocks which can include subducted oceanic crust and overlying sediments plus the lower continental crust.  Andesites, which are the most common rocks produced by Ruapehu eruptions, are differentiated products of basaltic magmas that may have become contaminated and mixed with magmas generated by partial melting of the surrounding crust.  In short, the higher the water content, the higher the explosivity of the eruption.

The fallout from eruptions is as follows:

Ash – less than 2mm diameter particles

Lapilli – 2-64mm diameter particles

Bombs – greater than 64mm diameter plastically deformed blobs of magma

Blocks – greater than 64mm diameter solid rock fragments

The temperatures of these rocks at eruption are 1100 – 1250 degrees Celcius

During the 1995/96 eruptions enough ash and lapilli built up on the rim of Crater Lake to allow an increase in lake water volume.  This debris, termed tephra, is unconsolidated and allowed as much as 1000 cubic metres per day to seep out of the lake prior to the 18 March 2007 lahar.

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Mount Ruapehu – An Overview

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Sometimes I just have to pinch myself to make sure I’m not dreaming.  How lucky am I to live on planet earth?  Air to breathe, soil on which to stand, crumble through my fingers and grow food, water to sustain life, a sun that delivers just the right amount of energy.  How luckier still to live on one of the planet’s most dynamic islands – volcanoes, glaciers, geysers, hot springs.

Mt Ruapehu is one of my favourite parts of New Zealand which I visit often and it was an obvious place to set my debut novel.   After gaining a Batchelor of Science in Earth Science through Massey University I decided to combine my love of geology with my love of reading by writing a novel using the mountain as the backdrop.

Fire in the Mountain is set on Mt Ruapehu which is an active stratovolcano, 250,000 years old and situated at the south west end of the Taupo Volcanic Zone where the earth is in a constant state of flux due to tectonic plate subduction processes.  The mountain is presently on alert level one which indicates some signs of unrest.  The mountain has more recently displayed good eruptions twice in the 1970s then in 1995 and 1996.  A significant but very small eruption occurred 18 March 2007 triggering the lahar of the same day which subsequently stole the limelight.  Six months later on 25 September 2007 an explosive eruption lasted only seven minutes during which ash, rocks and water spread across the summit areas.

You can visit Mt Ruapehu yourself via the webcam on http://www.geonet.org.nz.  Photos of the mountain are posted daily.  I’m not a great photo taker so there won’t be any on my blog, more’s the pity.

Fire in the Mountain (8)

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Set against the backdrop of an erupting volcano  in New Zealand’s North Island, Lana wrestles with her recent grief, for survival on the mountain and her future with a man whose past she was once a part of.  Woven through her narrative is Alfred’s story and the theft of war medals, and which Lana finds herself enmeshed in, further threatening her life.  Follow Lana as she tries to extricate herself from not only the mountain but her past.

Welcome to the eighth snippet of Fire in the Mountain

Lana knew that night would take a long time to fall, but even so with the land covered with snow and some moonlight able to get through, it would never get pitch black.  She began to think about the hut: the warmth, the fire, food and Paul.  Her stomp eased back into a trudge and she chanted a mantra in her head: trudge drag trudge drag.  Before long she’d broached the final brow and made out the dark shape of the hut.  A tiny spot of amber light was all she needed to give impetus to the final leg.

Fire in the Mountain (7)

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Set against the backdrop of an erupting volcano  in New Zealand’s North Island, Lana wrestles with her recent grief, for survival on the mountain and her future with a man whose past she was once a part of.  Woven through her narrative is Alfred’s story and the theft of war medals, and which Lana finds herself enmeshed in, further threatening her life.  Follow Lana as she tries to extricate herself from not only the mountain but her past.

Welcome to the seventh snippet of Fire in the Mountain

She could hear someone calling her but not using her name.  It should have been her mother but it was a man’s voice.

‘Lady, lady,’ called the voice.

‘Paul?’ she murmured.

‘Lady wake up,’ the voice said with urgency, a bit gruff.

Lana was waiting for Paul to kiss her.  How could he kiss her while calling lady at the same time?  She stirred but could not open her eyes.  She would not open them until she felt his tender lips on hers.  A sweet promise, so close, so close.

‘Lady,’ called Bill again.  The voice was not one she recognised.  She grunted as she forced her eyes open.  A figure, blurry, was making its way towards her slowly, clutching his side.

‘Oh,’ Lana moaned.  ‘What happened?’

‘You must have fell girl.’  He offered her one hand and grimaced as he held the other one fast to his side.  She didn’t take it but struggled into a sitting position.

‘Oh my head,’ she groaned, gently rubbing the back of it.  ‘No wait, I remember.  Your mates attacked me.  Where are they?  What’s going on?’

Fire in the Mountain (6)

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Set against the backdrop of an erupting volcano  in New Zealand’s North Island, Lana wrestles with her recent grief, for survival on the mountain and her future with a man whose past she was once a part of.  Woven through her narrative is Alfred’s story and the theft of war medals, and which Lana finds herself enmeshed in, further threatening her life.  Follow Lana as she tries to extricate herself from not only the mountain but her past.

Welcome to the sixth snippet of Fire in the Mountain

As he squatted a deep-seated rumble permeated the whole mountain, reverberating beneath his feet and right through his body.  A shrill scream caused him to look behind him just as a massive ejection of steam, ash and rocky blocks spewed above the mountain.  Arcs of white steam trailed the projectiles above the summit as hot air condensed into the cold.  Volcanic debris landed hundreds of metres from the centre of the eruption vent and rained down once again onto the lower slopes.

He was reasonably protected.  He’d been scaling the ridge which trended north east.  Therefore, at this moment with the explosion so momentous the debris flew more or less over him.  He expected to catch the wind once he’d reached the top so paused to cover up before he got there.  Now he was too late to traverse it, to get closer to the vent.  He gazed back down the mountain to the source of the scream.