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New Plymouth District Council.

Taranaki Stories 
Natural World - Volcanic Taranaki  
Mt Taranaki

Many Eruptions: Mount Taranaki is called the Egmont Volcano by geologists.

By Virginia Winder

 

Taranaki's mountain has a history of repetitive violence.


Massey University associate professor Vince Neall says Mt Taranaki, which geologists call the Egmont Volcano, has been formed by at least five major cone collapses.

 

This is a rarity in the volcanic world. "There have been these huge gravitational collapses, which are difficult for the human mind to comprehend," says the geologist.


"On at least five occasions in its history, a cone the size of the present Mt Taranaki has simply collapsed sideways like Mt St Helens did in 1980.


"Some volcanoes don't do that and some volcanoes might do it once in their history, but there are only a handful around the world that do it repeatedly. Egmont is one of those."


Others include, Mt Popocatepetl outside Mexico City, Mt Colima on the western Pacific coast of Mexico, Mt Shasta in California and Mt Rainier in Washington State.


Mapping volcanic history

Vince has spent his geology career studying Taranaki's volcanic history, and even chose it as his PhD topic in the 1960s.



Vince Neall
Vince Neall: The geologist says Mount Taranaki will erupt again - sometime.

Through his field research, he has found first-hand evidence of these early cone collapses.


"I have been privileged to have been involved in the mapping of these deposits that we didn't know the significance of before," Vince says.


"There is this incredibly complicated volcanic history to this mountain that we are still unravelling – it's 100 times more complicated than people portrayed prior to 1960. It's a challenge for us to work out the sequence of events; there would have literally been thousands of eruptions over its history."


Clues to past blasts

Vince says the road cuttings on the way up to the Stratford Plateau, show evidence of at least 20 bigger eruptions. "But there's a multiplicity of little ones between these, which have only left a millimetre of ash behind."


Even smaller ones, leave nothing.


He puts this in context by looking at the Mt Ruapehu eruptions of 1995 and 96. "We recorded over 30 lahars (wet flows of mud, sand and gravel), yet I can only show you one of these – all the rest have been erased by rivers. You will only see the recordings of the big events.


"That's why we drill cores in lakes and swamps to find the past history of volcanoes and, in between the ashes, you then have sediment and peat. We radiocarbon date the peat layers," he says.


All these clues show Mt Taranaki has been a wild one – and will be again.


"Of course, what's on everybody's mind was when was the last eruption?"


Ashes to ashes

Vince says there was a small eruption about AD1755, which created what is known as the Tahurangi Ash.


The last major hazardous eruption happened about AD1500, when several extremely hot clouds of gas and debris flowed from the crater and destroyed much of the forest on the north-western slopes.


About 150 years later, flying pumice buried a Maori campsite near the Stratford Mountain House.


At the beginning of the 21st century, Mt Taranaki appears to be peaceful. This is known for certain, via the seismic survey stations monitoring the mountain.


But residents should never be complacent.


The mountain is just asleep – not extinct. Whether future activity will be a big blast or a minor flare-up lies with the Earth.


Eruption will happen

However, Vince believes the next blow-up may be fairly small. "Compared with the literally thousands of eruptions, the big cone collapses have only occurred on five or ten occasions, so the more likely event to happen in the future will be further eruptions from the summit crater, with small collapses into surrounding gorges with volcanic mudflow, or lahars extending down the main river valleys."


Mt Taranaki first became active 130,000 years ago, which makes it the youngest of the region's volcanoes.


"The earliest volcanic activity preserved on land is Paritutu and the Sugar Loaf Islands," he says of the landscape features beside Port Taranaki in New Plymouth.

 

Paritutu and the Sugar Loaf Islands
Rocky Remnants: Paritutu and the Sugar Loaf Islands are the last vestiges of an ancient massive volcano.

 

These formed 1.75 million years ago, about the same time human beings evolved. That was also about the time the world became subject to the ice ages, with warm periods in between.


Stubble on the coast

"All of western Taranaki has been built up out of the sea by these volcanoes."


Paritutu and the Sugar Loaf Islands are remnants of something far larger. "They are literally the stubble of a volcano, where all the soft rocks have been eroded by the sea," Vince says. "These are the last vestiges of that volcanic centre."


Next up are the Kaitake and Pouakai ranges.

 

Kaitake Ranges

Kaitake Range: Active about 500,000 years ago.

 

The former, which is the backdrop to the township of Oakura, is thought to have been active about 500,000 years ago. "There have been hot hydro thermal solutions that have altered a lot of the rocks there and this makes them difficult to work with and to date," Vince says. 


"But one or two vestiges of lava flows there give us the date of half a million years."


Pouakai is about as old as Kaitake, but has had a more energetic life.


Ages of ranges

"Recent work that we have been doing indicates that Pouakai is probably of similar age to Kaitake, but it kept on being active until about 240,000 years ago.

 

Pouakai Range

Pouakai Range: Was active much longer than the Kaitake Range.

 

That built up an extensive apron of broken rock fragments around it," Vince says of the now extinct volcano.


When the "Egmont Volcano" arrived on the scene 130,000 years ago, it destroyed the southern two-thirds of the Pouakai ringplain. "The only remnant of it is the hills around Eltham."


On the other hand, Mt Taranaki's cloak is long and full.


"The ringplain that Egmont has built is many times the volume of the actual cone that we see within the Egmont National Park," Vince says. "This is evidence of all the previous cones that have collapsed."


Standing 2518 metres high, Mt Taranaki dominates the region's landscape. It also has one other feature over its sibling volcanoes.


While Paritutu, the Sugar Loaf Islands, Kaitake and Pouakai are all extinct, Mt Taranaki still has an active future. And it could be well be wild. New scientific evidence shows that Mt Taranaki erupted just 150 years ago - 100 years later than previously recorded.

 

Update 2005

Last eruption not so long ago

 

New scientific evidence shows that Mt Taranaki erupted just 150 years ago - 100 years later than previously recorded.

 

That is according to PhD student Thomas Platz, who is a recipient of the George Mason Charitable Trust Scholarship administered by the Taranaki Research Centre in Puke Ariki.

 

Mr Platz and fellow doctorate and scholarship studen Michael Turner gave presentations about their research at the New Plymouth Civic Chambers yesterday afternoon.

 

Mr Platz said that, until now, scientists believed the mountain's last blast was in 1775. That created what is known as the Tahurangi Ash.

 

But during his studies on an earlier eruption, Mr Platz came across physical evidence of a small eruption in 1850s or 1860s.

 

"It's basically different from any previous eruption," he said yesterday. "It has its own chemical signature."

 

Mr Platz said it appeared that a lava dome formed on the western side of the crater. "It cooled dow and, maybe ten years later, it collapsed."

 

An old black-and-white photograph shows the dome debris came to rest about 800km above sea level.  That meant it travelled 4-5km down the mountain.

 

To back up this new evidence, Mr Platz would like tohear from any historians who have uncovered diary entries or newspaper records of reported earth tremors in the 1850s or '60s.

 

"It was pretty small," he said of the volcanic activity.

 

His discovery comes hot on the heels of fresh information about the number and frequency of eruptions on Mt Taranaki.

 

Core samples had shown almost 100 ash layers, suggesting the mountain had erupted at least once every 90 years, on average, over 9000 years.




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BOOK RESOURCES

Daily News, Our Park: 100 years of the Egmont National Park, (2000), New Plymouth: Taranaki Newspapers

 

Ivon Watkins-Dow, The Life and Times of Paritutu, (1967), New Plymouth

 

Ivon Watkins-Dow, and Vince Neall, Volcanic Hazards at Egmont Volcano, (1991), Palmerston North: Ministry of Civil Defence.

 

Patterson, Des, Future Volcanic Activity in Taranaki: Likely Impact and Effect on Taranaki Infrastructure and the Implications for Civil Defence and Emergency Response Contingency Plans, (1984), New Plymouth: Taranaki United Council.


Taranaki Regional Council, Taranaki Regional Volcanic Contingency Plan 2000, (2000), Stratford: The Council.


ARCHIVES

An agreement between the Taranaki Provincial Council and a local group signed on 29 April 1864 allowing the group to mine sand and iron ore from the foreshore at Bell Block and the Paritutu areas.


WEBLINKS

Puke Ariki is not responsible for the content of these external websites.

 

Egmont National Park - Department of Conservation site

 

GeoNet - The New Zealand GeoNet Project provides real-time monitoring of earthquake, volcano, landslide and tsunami hazards.

 

GeoNet Mt Taranaki webcam - realtime images of Mt Taranaki

 

Geological Society of New Zealand - The Geological Society of New Zealand aims to encourage the advancement of geology in New Zealand

 

Manganui Ski Field - Stratford Mountain Club website

 

Skiing the Pacific Ring of Fire: Taranaki - Ski Taranaki!


Sugar Loaf Marine Park


RELATED TARANAKI STORIES

Volcanic Taranaki

 

EDUCATION

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Mount Taranaki Interactive

 

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Taranaki Geology (PDF 38kb)


PLACES TO VISIT

Mt Taranaki/Egmont Volcano

Dawson Falls Visitor Centre
RD 29
Kaponga
Hawera

Phone: 025 430 248

Email: bthurston@doc.govt.nz

 

North Egmont Visitor Centre
Egmont Road
RD 6
Inglewood
Phone: 06 756 0990
Fax: 06 756 0991

 

Mountain Guides

Adventure Dynamics Website: www.adventuredynamics.co.nz


MacAlpine Guides - Ian MacAlpine

Website: www.macalpineguides.com Email: alpineguidesmac@xtra.co.nz Mobile: 027 441 7042

 

Mountain Guides Mount Egmont - Chris Prudden

Website: www.mountainguides.co.nz Email: mguide@voyager.co.nz Mobile: 025 474 510

5 day mountaineering programmes.



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