Sunday, September 26, 2010

New Ocean Forming as Africa Splits Apart, Scientists Pinpointing Where Volcanic Eruptions Could Strike


Map of the Afar region. Inset: Africa
 Map of Afar and Africa


A better way to pinpoint where volcanic eruptions are likely to occur has been produced by an international team of geophysicists.

Scientists from the universities of Leeds, Purdue, Indiana and Addis Ababa, investigated volcanic activity occurring in the remote Afar desert of Northern Ethiopia between 2005 and 2009.

By studying a rare sequence of 13 magmatic events – where hot molten rock was intruded into a crack between the African and Arabian plates – they found that the location of each intrusion was not random. They showed that they were linked because each event changed the amount of tension in the earth's crust.

The findings, published in Nature Geoscience, will help scientists to more accurately predict where volcanic eruptions could strike and contribute to efforts to limit the damage they can cause.

Lead author Dr Ian Hamling, who completed the analysis as part of his PhD in the School of Earth and Environment at the University of Leeds said: "It's been known for some time that a large earthquake has a role to play in triggering subsequent earthquakes, but until now, our knowledge of volcanic events has been based on isolated cases. We have demonstrated that volcanic eruptions can influence each other. This will help us predict where future volcanic eruptions are likely to happen."

The team studied the region around a large volcanic dyke – a vertical crack which is created when Magma seeps from underground through rifts in the surface of the earth – which erupted in the Afar desert in September 2005.

The Magma - hot molten rock - was injected along the dyke between depths of 2 and 9 km, and altered the tension of the earth. The team was able to watch the 12 smaller dykes that subsequently took place in the same region over a four year period.

By monitoring levels of tension in the ground near where each dyke was intruded they found that subsequent eruptions were more likely in places where the tension increases.

Dr Hamling said: "If you look at this year's eruptions at Ejafjallajokull in Iceland, by estimating the tension in the crust at other volcanoes nearby, you could estimate whether the likelihood of them eruption has increased or decreased. Knowing the state of stress in this way won't tell you when an eruption will happen, but it will give a better idea of where it is most likely to occur."

 Erta 'Ale lava lake


The Afar Rift Consortium is a project funded by the UK Natural Environment Research Council (NERC). The consortium is made up of scientists from the Universities of Leeds, Bristol, Oxford, Edinburgh, and Cambridge, and the British Geological Survey, with partners in Ethiopia, France and the US. Its aim is to conduct a major set of experiments in this unique natural laboratory, to further understand the processes involved in shaping the surface of the Earth.

In the remote Afar depression in northern Ethiopia, the African Continent is slowly splitting apart and a new ocean is forming.

In September 2005, a series of fissures opened along the Afar Depression. Over 10 days, the rift pulled apart by eight metres. Local people told of a series of earthquakes and how ash darkened the air for three days.

This process of ocean formation is normally hidden deep beneath the seas, but in Afar we can walk across the region as the Earth's surface splits apart.

The paper 'Stress transfer between thirteen successive dyke intrusions in Ethiopia' by Drs Ian Hamling and Tim Wright of the School of Earth and Environment at the University of Leeds; Eric Calais and Laura Bennati of the Department of Earth and Atmospheric Sciences at Purdue University, Indiana, and Elias Lewi of the Geophysical Obervatory, Addis Ababa University, Ethiopia, is available online in Nature Geoscience.

The 2008 Research Assessment Exercise showed the University of Leeds to be the UK's eighth biggest research powerhouse. The University is one of the largest higher education institutions in the UK and a member of the Russell Group of research-intensive universities. The University's vision is to secure a place among the world's top 50 by 2015.

Ian Hamling was funded through a studentship from the UK National Centre for Earth Observation, and is now a postdoctoral researcher at the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy. Tim Wright is a Royal Society research fellow at the School of Earth and Environment at the University of Leeds and the principle investigator of the NERC-funded Afar Rift Consortium.

Contacts and sources:

No comments:

Post a Comment