Monday, September 27, 2010

[Geology2] Volcano News 09/27/2010

Pinpointing where volcanic eruptions could strike

by bjs on 26. Sep, 2010 

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.

he 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."



Ancient volcanic field reawakens in Saudi Arabia

In 2009, more than 30,000 earthquakes struck an ancient lava field, opening up a five-mile long crevice. Sensors shoow that magma has risen to roughly a mile below the surface of the Earth, and eruptions remain possible.

The view of one of several volcanos in the area of Al-Aayiss near the Saudi city Madina, west of the oil-rich kingdom. Several earthquakes were registered in the area including one on May 20, 2009 with a magnitude of 5,4,



By Charles Q. Choi, Our AmazingPlanet Contributor / September 26, 2010

A swarm of thousands of earthquakes that struck the corner of Saudi Arabia nearest to Egypt in 2009 helped reveal that the area is unexpectedly volcanically active, scientists now report.

The seismic readings that researchers managed to collect from these quakes could help predict when volcanoes might erupt in the future, investigators added.

Scientists had largely thought northwest Saudi Arabia was quiet, geologically speaking. Few earthquakes and few volcanic eruptions have been recorded there in the past millennium.

However, between April and June 2009, more than 30,000 earthquakes struck an ancient lava field there named Harrat Lunayyir, with 19 earthquakes of magnitude 4 or greater striking at the swarm's peak on May 19, including a magnitude 5.4 quake that fractured walls in the town of Al Ays. Sensors even suggested that a volcanic eruption was possible. Alarmed, the Saudi Arabian government then evacuated 40,000 people from the region.

Part of Red Sea Parting

The lava field of Harrat Lunayyir is part of a "lava province" roughly 70,000 square miles (180,000 square kilometers) in size that began forming 30 million years ago when Arabia split from Africa, rifting that helped create the Red Sea. Harrat Lunayyir was previously considered inactive because of its location on the margins of the continental rift, nearly 120 miles (200 kilometers) away from the active center of spreading beneath the Red Sea.

Still, "the Red Sea rift is a very active place to start with, with a chain of volcanoes down the middle of it that we're rarely aware of because they are underwater," said researcher John Pallister, a volcanologist and chief of the U.S. Geological Survey's volcano disaster assistance program. "When continents are being pulled apart as you have there, you'll often see intrusions of magma on the shoulders of the rift."

The researchers discovered a roughly 2-mile-long (3-km-long) rupture had opened up in the area and widened to 5 miles (8 km) long during the most powerful quake. Satellite radar images suggested the most likely cause of this fault was magma intruding upward over a 6-mile-long (10-km-long) stretch.

Based on these findings, on June 19, 2009, the researchers forecast a moderate chance of a volcanic eruption and a low probability of magnitude 5 or greater earthquakes in the two months following. A decline of seismic activity by August 2009 led the scientists to conclude the crisis had ended, allowing evacuees to return to their homes and daily lives.

Magma rises

Still, now that magma has risen to shallow levels roughly a mile (2 kilometers) below the surface of the Earth, eruptions remain possible, and the authorities have to remain vigilant, the researchers said.

"It is more likely that we'll get additional intrusions of magma and potentially even an eruption in this area — the pathway is prepared," Pallister told Our Amazing Planet.

The highly detailed readings the Saudi Geological Survey collected from these quakes might be able to help scientists forecast volcanic eruptions in the future, Pallister added.

Volcanic quakes often generate a mix of high- and low-frequency seismic waves that could yield clues as to when an eruption might occur. These signals are often dulled by the nature of the earth they pass through, but when it came to the Arabian quakes, they were detected through the crystalline rocks of the area quite clearly. The low-frequency seismic waves detected during the quakes seemed to show magma flowing under the earth, while the high-frequency waves indicated fracturing of crystalline rocks as magma crept toward the surface.

"Understanding what these signals mean could prove instrumental to forecasting what can be deadly events worldwide," Pallister said.

The scientists detailed their findings online Sept. 26 in the journal Nature Geoscience.



Iceland's Bárðarbunga volcano shows more activity lately

Sunday, September 26, 2010 - 14:21

Bárðarbunga is a powerful stratovolcano in Iceland and is located under the ice cap of Vatnajökull glacier. With a massive high of 6591 feet above sea level that makes it the highest mountain in Iceland it also makes for some powerful volanic activity when it erupts.

Iceland's Bárðarbunga volcano is said to erupt every 250-600 years if scientists are correct. What many dont know is that the most powerful volcano eruption on earth happened at Bárðarbunga some time ago.

For those that believe in evolution it could be around 8000 years ago but for those that believe in creation it could be around 3000 years ago, no one knows exactly when but the last time Bárðarbunga erupted it caused lava to cover an area of 950 square kilometers.

It is believed that Bárðarbunga will erupt sometime in the near future.

In the picture above you can see the activity rising in the last couple of days.


Got Penguins? 

Penguin News Today
The Science of Penguins
Gentoo Penguins of Gars O'Higgins Station, Antarctica


Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe


No comments:

Post a Comment