 Vanuatu island to evacuate again as volcano erupts Wellington, New Zealand (AFP) April 13, 2018 - Villagers on the Vanuatu island of Ambae were facing their second evacuation in seven months Friday after a volcano rumbled back to life and rained ash on their homes. Authorities in the Pacific nation have declared a state of emergency on the northern island, where 11,000 people were forced to leave last September. Many have only just returned home but the Vanuatu Meteorology and Geo-Hazards Department said the Manaro Voui volcano was undergoing a level three eruption, the mid-point in a five-level scale. National disaster ministry director general Jesse Benjamin said any evacuation would be more orderly than the one carried out in September, when a flotilla of small vessels were pressed into service to rush people off the island. "Last year's evacuation was conducted in haste, amidst fears of a major eruption," he told the Daily Post newspaper. "There is some dissatisfaction about the way we moved people at the time. This time we will be evacuating people from the severely affected communities first, before the less affected. "The government is worried about the safety of the people." Vanuatu, which has a population of about 280,000 spread over 65 inhabited islands, is regarded as one of the most disaster-prone countries in the world. It sits on the so-called "Pacific Rim of Fire" making it vulnerable to strong earthquakes and volcanic eruptions, while powerful cyclones also regularly lash the islands.
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Scientists have identified the temperature at which cooling magma breaks into the geometric columns that form Giant's Causeway in Northern Ireland and Devils Postpile in California.
At the Giant's Causeway, thousands of basaltic columns form a platform along the coast. The geologic phenomenon has inspired a number of mythologies through history.
The columned deposit was precipitated by an ancient volcanic fissure eruption. But until now, scientists weren't sure of the cooling patterns that allowed the magma to form some 40,000 columns.
To find out how the rocks cracked and formed the columns, scientists at the University of Liverpool built an apparatus to help them replicate the formation process. The contraption holds cooling lava in a press. As it contracts, cracks and forms columns, scientists can watch and measure the changes in temperature.
When rocks cooled to between 90 and 140 degrees Celsius below the threshold at which magma crystallizes into a rock, 980 degrees Celsius, they began to fracture. Thus, researchers believe the columns found at Giant's Causeway and Devils Postpile formed at temperatures ranging from 840 to 890 degrees Celsius.
"The temperature at which magma cools to form these columnar joints is a question that has fascinated the world of geology for a very long time," Yan Lavallée, a professor of volcanology at Liverpool, said in a news release. "We have been wanting to know whether the temperature of the lava that causes the fractures was hot, warm or cold."
The answer is that the columns were formed from hot rocks, but after the magma had solidified.
Researchers published their findings on Thursday in the journal Nature Communications.
"Knowing the point at which cooling magma fractures is critical, as -- beyond leading to the incision of this stunning geometrical feature -- it initiates fluid circulation in the fracture network," said Jackie Kendrick, a post-doctoral researcher at Liverpool. "Fluid flow controls heat transfer in volcanic systems, which can be harnessed for geothermal energy production. So the findings have tremendous applications for both volcanology and geothermal research."
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Great magma eruptions had 2 sources
Helsinki, Finland (SPX) Apr 11, 2018
Research at Finnish Museum of Natural History may explain controversies related to great magma eruptions.
The modern continents were formed when Pangea broke into pieces in the Mesozoic time. The splitting of Africa from Antarctica started with great magma eruptions that flooded over an area millions of square kilometres wide.
Remnants of the ancient ocean of lava, the so-called Karoo magma province, are still widespread in southern Africa and have been also discovered in Antarctica. Dr Arto ... read more
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