Video | Business Headlines | Internet | Science | Scientific Ethics | Technology | Search

 


Rangitoto research prompts rethink of Auckland volcanoes


11 April 2013

Rangitoto research prompts rethink of Auckland volcanoes

University of Auckland scientists have discovered that Rangitoto erupted not once or twice as previously believed, but multiple times over a period of 1,000 years, prompting a rethink of how Auckland volcanoes may behave in the future.

Rangitoto is the most recent volcano to erupt in Auckland. “Previously Rangitoto was thought to have formed 550-500 years ago,” explains lead researcher Associate Professor Phil Shane.

“We have found that in fact, Rangitoto erupted intermittently or semi-continuously from about 1,500 years ago to 500 years ago. That’s much longer than we’ve traditionally believed for basaltic volcanoes of this kind, not only in Auckland but anywhere in the world,”

The findings are important for understanding the risk posed by volcanoes in the Auckland region, and perhaps elsewhere. “The old paradigm was that these volcanoes erupt suddenly in a new location each time, and only live for months to a year or two,” says Dr Shane. “This needs to be revisited in light of the new Rangitoto history of activity.”

It may be that there is something unique about the location where Rangitoto erupted, but based on the findings: “We cannot rule out long-lived activity in the future, or eruptions at sites that have experienced previous activity. The Auckland volcanic field could be going into a new mode of operation. If so we need to think about hazard planning and risk in a very different way.”

The scientists found frequent small pulses of volcanic activity at Rangitoto from around 1,500 years ago all the way up to more substantial eruptions around 550 and 500 years later. These latter two eruptions have been known about for some time, but the earlier activity is an entirely new discovery.

The work was done by examining the deposition of Rangitoto ash in the sediments of nearby Lake Pupuke. The sediments have built up slowly over time and can be very accurately dated. By studying the abundance and chemical fingerprint of tiny volcanic glass shards in the sediment, the researchers could determine when the eruptions occurred.

This is an entirely new approach. Most studies use radiocarbon dating to determine the age of samples taken directly from a volcano. However lake bed sediments can be dated on a much finer scale, and may be able to detect evidence of activity that cannot be seen on the volcano itself because it is buried by later eruptions.

Human activity has disrupted the younger sediments in the lake bed so the scientists cannot say with confidence whether there was any further activity at Rangitoto in the past 500 years, and they plan future work to address this.

The study is part of an ongoing research project into the history of volcanic eruptions and lakes in the Auckland region involving Dr Phil Shane, Associate Professor Paul Augustinus, and PhD student Ola Zawalna-Geer, all from The University of Auckland’s School of Environment. The work has been published in the latest issue of the Journal of Volcanology and Geothermal Research.

ends

© Scoop Media

 
 
 
 
 
Business Headlines | Sci-Tech Headlines

 

Half Empty: Fonterra's 2017 Opening Forecast Below Expectations

Fonterra Cooperative Group raised its forecast farmgate milk payout for next season by less than expected as the world's largest dairy exporter predicts lower prices will crimp production and supply will pick up. The New Zealand dollar fell. More>>

ALSO:

Pest Control: Mouse Blitz Team Leaves For Antipodes

The Million Dollar Mouse project to rid Antipodes Island of mice is underway with the departure of a rodent eradication team to the remote nature reserve and World Heritage Area. More>>

Gongs Got: Canon Media Awards & NZ Radio Awards Happen

Radio NZ: RNZ website The Wireless, which is co-funded by NZ On Air, was named best website, while Toby Manhire and Toby Morris won the best opinion general writing section for their weekly column on rnz.co.nz and Tess McClure won the best junior feature writer section. More>>

ALSO:

Pre-Budget: Debt Focus Risks Losing Opportunity To Stoke Economy

The Treasury is likely to upgrade its forecasts for economic growth in Budget 2016 next week but Finance Minister Bill English has already signalled that more of his focus is on debt repayment than on fiscal stimulus or tax cuts... More>>

ALSO:

Fulton Hogan's Heroes: Managing Director Nick Miller Resigns

Fulton Hogan managing director Nick Miller will leave the privately owned construction company after seven years in charge. The Dunedin-based company has kicked off a search for a replacement, and Miller will stay on at the helm until March next year, or until a successor has been appointed and a transition period completed. More>>

ALSO:

Gordon Campbell: On Electricity, Executions, And Bob Dylan

The Electricity Authority has unveiled the final version of its pricing plan for electricity transmission. This will change the way transmission prices (which comprise about 10% of the average power bill) are computed, and will add hundreds of dollars a year to power bills for many ordinary consumers. More>>

ALSO:

Half Empty: Fonterra NZ, Australia Milk Collection Drops In Season

Fonterra Cooperative Group says milk collection is down in New Zealand and Australia, its two largest markets, in the first 11 months of the season during a period of weak dairy prices. More>>

ALSO:

Get More From Scoop

 
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news