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

 

Economic Update: RBNZ Says Rate Cut Seems Likely

The Reserve Bank will likely cut interest rates further as a persistently strong kiwi dollar makes it difficult for the bank to meet its inflation target, it said. The local currency fell. More>>

ALSO:

House Price Action Plan: RBNZ Signals National Lending Restrictions

The central bank wants to cap bank lending to property investors with a deposit of less than 40 percent at 5 percent and restore the 10 percent limit for owner-occupiers wanting to take out a mortgage with a deposit of less than 20 percent, according to a consultation paper released today. More>>

ALSO:

Sparks Fly: Gordon Campbell On China Steel Dumping Allegations

No doubt, officials on the China desk at MFAT have prided themselves on fashioning a niche position for New Zealand right in between the US and China – and leveraging off both of them! Well, as the Aussies would say, of MFAT: tell ‘em they’re dreaming. More>>

ALSO:

Loan Sharks: Finance Companies Found Guilty Of Breaching Fair Trading Act

Finance companies Budget Loans and Evolution Finance, run by former 1980s corporate high-flyer Allan Hawkins, have been found guilty of 106 charges of breaching the Fair Trading Act for misleading 21 borrowers while enforcing loan contracts. More>>

ALSO:

Post Panama Papers: Govt To Adopt Shewan's Foreign Trust Recommendations

The government will adopt all of the recommendations from former PwC chairman John Shewan to increase disclosure and introduce a register for foreign trusts with new legislation to be introduced next month. More>>

ALSO:

The Price Of Cheese: Cheddar At Eight-Year Low

Food prices decreased 0.5 percent in the year to June 2016, influenced by lower grocery food prices (down 2.3 percent), Statistics New Zealand said today. Compared with June 2015, cheese prices were down 9.5 percent, fresh milk was down 3.9 percent, and yoghurt was down 9.2 percent. More>>

ALSO:

Financial Advisers: New 'Customer-First' Obligations

Goldsmith plans to do away with the current adviser designations which he says have been "unsatisfactory" in that some advisers are obliged to disclose potential conflicts of interest and act in their customers' best interests, but others are not. More>>

ALSO:

Get More From Scoop

 
 
 
 
 
 
 
 
 
Sci-Tech
Search Scoop  
 
 
Powered by Vodafone
NZ independent news