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Science, Maths & Technology

Getting geophysical in Central America

Updated Thursday 19th March 2009

Hazel Rymer visits volcanoes in Costa Rica and Nicaragua to take geophysical measurements

I left a cold and snowy UK earlier this month to go back to Central America to continue the geophysical measurements in Costa Rica and Nicaragua. The journey over was long but uneventful and this time US customs decided not to open the cases (breaking the locks) to check that the instruments were all in order with the paperwork. Why, oh why can’t they have a transit lounge at Miami so that you don’t have to immigrate for just a few hours on the way to Central America?

On arrival in Costa Rica, the weather was warm, but windy and the volcanoes, which should dominate the skyline, were obscured in cloud. The next couple of days were spent preparing equipment, talking with colleagues at the local observatory, OVSICORI (Observatorio Vulcanológico y Sismológico de Costa Rica) part of the National University, and giving a lecture on our results so far.

We spent a day trying to get up Turrialba volcano, but the weather was so bad that a landslide caused by the rain blocked the road and after an hour or so of queuing and waiting, although we got through, it was clear that it was too dangerous to proceed. It is so frustrating to get so close and then not to get to the summit to make our measurements. Turrialba has increased its gas output over the last few years, and we have been monitoring the gravity field at the summit region to see whether a new batch of magma is rising or whether this is just an escape of gas from the magma body, which has been cooling at the summit since the last eruption in 1866.

Masaya volcano from the airport Copyrighted image Icon Copyright: by Hazel Rymer © copyright Hazel Rymer
Masaya volcano from the airport

 

On Sunday, it was time to leave the relatively cool breeze in Costa Rica and go up to Masaya, Nicaragua, where the elevation is lower and the climate at this time of year is much drier and hotter. The volcano is persistently degassing and we are working with a groups of Earthwatch volunteers to collect geophysical and ecological biodiversity data on the environmental effects and changing activity at Masaya Volcano.

Earthwatch volunteers Copyrighted image Icon Copyright: Hazel Rymer
Earthwatch volunteers taking gravity, GPS and magnetic measurements.[Image by Hazel Rymer © copyright Hazel Rymer]

We have a network of gravity stations, which we measure every year and we have shown a correlation between a reduction in gravity at the summit crater area and an increase in gas flux. Our earlier work has been published already and is freely available – "Gravity changes and passive SO2 degassing at the Masaya caldera complex, Nicaragua".

Installing tiltmeters Copyrighted image Icon Copyright: by Hazel Rymer © copyright Hazel Rymer
Volunteers installing a tiltmeter at the bunker near the crater.
 

This year, we are setting up continuously recording gravity meters, making dynamic gravity measurements, magnetic, differential GPS and SP measurements to investigate the level of the sub-surface magma and the amount of gas within it. We are also conducting biodiversity studies to investigate the effects of the persistent degassing on the flora and fauna.

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