Big NZ quakes shown to influence atmospheric CO2

Ancient evidence recovered from the bottom of a South Island lake has suggested large earthquakes can influence the amount of carbon dioxide in the Earth's atmosphere.

A new study by Kiwi and UK scientists found that big quakes unleashed along the high-risk Alpine Fault had both mobilised and buried large amounts of carbon - a natural process that might remove CO2 from the atmosphere.

The researchers examined sediments that had accumulated over the past thousand years at the bottom of Lake Paringa in the Southern Alps.

An analysis of the sediments, recording the level of carbon isotopes before and after past quakes, indicated that shakes on the fault had produced nearly half of the carbon in the biosphere released from the alps.

Simulations of quake-triggered landslides suggested that some 14 million tonnes of carbon were released during each Alpine Fault earthquake.

Yet, their findings showed these same earthquakes could also draw carbon out of the atmosphere if that carbon was transported to lake and ocean basins.

"Lush vegetation on the mountains draws carbon dioxide from the atmosphere," said Dr Jamie Howarth, of Victoria University of Wellington's School of Geography, Environment and Earth Sciences.

"In an earthquake, this vegetation is caught up in landslides, which sends the vegetation and the carbon to rivers, which in turn transport it to lakes and ocean basins where it is rapidly buried, removing it from the atmosphere."

This research was significant because it shows a clear link between tectonic activity and the climate on Earth.

Co-author Sean Fitzsimons, of the University of Otago, said the discovery shed more light on the natural inter-play between earth and atmosphere.

"These findings tell us that the development of mountains plays a critical role in the global carbon cycle over millions of years and provide a piece of the puzzle in understanding how atmospheric carbon is regulated by earth surface processes."

The study, just published in the journal Nature Geoscience, also involved researchers from GNS Science and Durham University in the UK.