Seafloor volcanoes surprise

15 May 2012
Sonar was used to map the Monowai volcano, near Tonga

Sonar was used to map the Monowai volcano, near Tonga

Volcanoes on the seafloor can grow or collapse tens of metres in just a few days, a new study has found, suggesting that that the seabed is much more unstable than previously thought.

Researchers, led by Professor Tony Watts of Oxford University’s Department of Earth Sciences, report how they surveyed the topography of the active Monowai volcano, a submarine volcano on the southwest Pacific Ocean floor near Tonga, in May and June 2011.

Repeated sonar mapping of the seafloor carried out over a fortnight showed that whilst some parts of the volcano had collapsed by almost 19 metres elsewhere fresh eruptions of lava had raised the volcano’s height by up to 72 metres.

Because they are underwater, and so difficult to study, little is known about how submarine volcanoes evolve or the frequency with which they erupt and grow. This new research suggests that these volcanoes could be rapidly ‘pulsating’, making the seafloor environment much more dynamic than anyone suspected; a finding that has implications for understanding what causes tsunamis.

‘I've spent my career studying the seabed and have generally thought it pretty stable so it's stunning to see so much change in such a short space of time,’ said Professor Tony Watts of Oxford University’s Department of Earth Sciences.

‘Any movement on the seabed has the potential to create a tsunami. An earthquake suddenly dislocates the seabed. Here a violent disturbance lasted five days with magma oozing out which might be too slow to trigger a tsunami - but it's unknown. This is a violent exchange of rock into the water - it could destabilise the cone and cause a landslide which in principle could cause a tsunami.’

A report of the research, entitled ‘Rapid rates of growth and collapse of Monowai submarine volcano in the Kermadec Arc’, is published online in this week’s Nature Geoscience.

 
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