Saturday, April 28, 2007
Volcano eruptions from the past created quite a blast!
The giant prehistoric eruptions, they believe, may have been the catalyst that pushed Greenland and northwest Europe apart to create the North Atlantic Ocean. "There has been evidence in the marine record of this period of global warming, and evidence in the geological record of the eruptions at roughly the same time, but until now there has been no direct link between the two," says Professor Robert Duncan of Oregon State University, who worked on the study.
Duncan and a team of international scientists say the volcanoes erupted off the coast of Greenland and in the western British Isles about 55 million years ago, spewing carbon dioxide and methane into the atmosphere. That triggered a 222,000-year period of warming that raised sea surface temperatures by 5°C in the tropics and more than 6°C in the Arctic and increased the acidity of the oceans.The resulting 'planetary emergency', as scientists have called it, wiped out 30-50% of the planet's deep sea creatures.
"We think the first volcanic eruptions began about 61 million years ago and then it took another 5 million years for the mantle to weaken, the continent to thin and the molten material to rise to the surface," Duncan says. "It was like lifting a lid. The plate came apart and gave birth to the North Atlantic Ocean." Birth of an oceanScientists made the link between the volcanoes and the warming period, known as the Palaeocene-Eocene thermal maximum, by matching layers of ash in east Greenland with those in marine sediments in the Atlantic Ocean. They think greenhouse gases from lava flows and the heating of organic-rich sediments along the eastern edge of Greenland caused the global warming and changes in ocean chemistry.
While these volcanic eruptions caused warming of the atmosphere, they are extremely rare, scientists say. Some more recent volcanoes, such as the eruption of Mount Tambora in Indonesia, actually cooled the Earth by adding more sulfate aerosols to the upper atmosphere, which reflected sunlight back into space, says Dr Ellie Highwood, senior lecturer in climate physics at the UK's University of Reading. "The type of volcano eruption described here has not been seen over the past 1000 years, and therefore volcanoes are unlikely to have contributed significantly to recent climate change," Highwood says.
An underwater volcano erupted near Iwojima
A fishing boat from Kochi Prefecture spotted the unusual sea color and smoke, and informed the coast guard around 10 a.m. Monday, they said.
Sunday, April 22, 2007
Colombian volcano erupts, forcing evacuation
The Nevado del Huila volcano's eruptions were its first on record since Colombia was colonized by the Spanish 500 years ago.
There are about 10,000 people living in the area around the volcano, and about 3,500 had been evacuated, Luz Amanda Pulido, director of the national disaster office, told The Associated Press after flying over the volcano in southwest Colombia.
There were no reports of deaths or injuries.
The eruption sent an avalanche of rocks down the volcano's sides and into the Paez and Simbola rivers, causing them to flood.
"The bridges were swept away, the highway used by the indigenous in the zone was destroyed for various kilometers (miles) and the problem we have now is the lack of a route to deliver goods and medicines to the population," Police Gen. Orlando Paez said.
Experts were not ruling out more eruptions.
"The seismic activity remains light but permanent, and we can't rule out another bigger event in the next hours or days," said Mario Ballesteros, director of the government's Institute for Geology and Mining.
The Nevado del Huila, which is topped with a crown of ice, is Colombia's third-highest peak at 18,484 feet. Located 170 miles southwest of Bogota, it became active again in March with a series of internal rumblings.
In 1985, the town of Armero was wiped from the map and 25,000 people were killed when another volcano, the Nevado del Ruiz, exploded and set off a series of mudslides. It was Colombia's worst natural disaster.
Sunday, April 15, 2007
Bulusan volcano, in the Phillippines spews out ashes!
Breaking three months of silence, 1,560-meter (5,149-foot) Mount Bulusan, one of the country's 22 active volcanos, belched ash and smoke for more than 20 minutes and rained ash on at least seven villages, the Philippine Institute of Volcanology and Seismology said.
Mayor Edwin Hamor of Casiguran town, at the base of the volcano, said visitors applauded and snapped pictures of the huge, mushroom-shaped ash plume that suddenly gushed out of Bulusan into a cloudless morning sky.
"It was very beautiful. Everybody was awed," Hamor told The Associated Press by telephone.
He said he rushed to a village hit by ashfall to help distribute masks to protect against lung ailments that could be caused by the volcanic ash.
He also ordered a village leader to turn away tourists from a resort if it could be hit by the ashfall.
Bulusan, about 390 kilometers (240 miles) southeast of Manila, came back to life in March and has been intermittently expelling ash and steam. It last spewed ash in January, according to volcanologists.
The latest activity may signal another bout of ash expulsions in the coming weeks, they said, adding that they would maintain the lowest alert level for the volcano despite its renewed unrest.
Villagers were warned against venturing into a four-kilometer (2.5-mile) "permanent danger zone" around the volcano.
The Philippine archipelago lies on the Pacific Ocean's "Ring of Fire," where volcanic activity and earthquakes are common.
In December, typhoon-triggered mudslides along the slopes of nearby Mayon volcano buried entire villages, killing more than 1,000 people.
Reunion Island volcano is erupting!
Eruptions on the Piton de la Fournaise have intensified since earlier this week and have volcanologists worried that cracks could be developing in the side of the mountain, the Sydney Herald Sun reported.
Reports from nearby Madagascar indicate rivers of lava flowing from the mountain and a Madagascar Web site said sulfur gas sent 50 children to the hospital.
Piton de la Fournaise means "Mountain of the Furnace," and is considered one of the most active volcanoes in the world.
Friday, April 06, 2007
La Reunion volcano offers quite a show
The red hot lava cut roads in half, damaged homes and created huge clouds of steam as it flowed into the Indian Ocean.
But the islanders are used to the spectacle. It is the third eruption of the Piton de la Fournaise or 'Mountain of the Furnace' this year alone.
About 50 teenagers were taken to hospital from three schools in Saint Joseph with respiratory problems caused by the volcano's sulpher fumes, according to Clicanoo.com, the online newspaper of La Reunion.
Researchers on the island are concerned the recent activity may be creating more cracks lower down the volcano, which will allow the molten lava to spread further.
The volcano is about 530,000 years old and has erupted an estimated 170 times since the mid 17th century.
La Reunion is a small island wedged between Madagascar and Mauritius. It is one of twenty-six regions of France and President Jacques Chirac is the head of state.
The 777,000 island inhabitants once prospered from the cultivation of sugar cane, but tourism and financial aid from Paris now underpin its economy.
Evidence shows Egyptian cities have been destroyed by volcanoes
The archaeological team, led by Mohamed Abdel Maqsoud of Egypt's Supreme Council for Antiquities, found houses, military structures, and tombs encased in ash near the ancient Egyptian fortress of Tharo, on the Horus military road.
Tharo is located close to El Qantara, where the Nile Delta meets the Sinai Peninsula.
Zahi Hawass, secretary general of the council, said the ash hailed from Santorini, an eastern Mediterranean volcano that has been linked to the myth of Atlantis.
He said the new find seemed to confirm accounts from ancient artwork and documents that recount the destruction of coastal cities in Egypt and Palestine during the 15th dynasty (1650-1550 BC), when foreigners known as the Hyksos ruled Egypt.
He said it was possible that Trade winds might have carried a blizzard of ash to Egypt from Santorini, located about 700 miles (1,100 kilometers) from Tharo.
Archaeologists also found a fort with four mud-brick towers dating to Egypt's 18th dynasty (around 1550 to 1307 BC).
Hawass said the fort corresponded to reliefs found in the ancient temple of Karnak in Luxor.
The sculptures describe Egypt's strategy to defend its eastern borders against future invasions by the Hyksos, who are thought to have been Semitic nomads from Syria and Palestine.
"It's very significant. There are only a limited number of sites linked to the Hyksos," National Geographic quoted Salima Ikram, a professor of Egyptology at the American University in Cairo as saying.
Ikram said the archaeological team had used "holistic archeology” incorporating geology and climatology in addition to archeology, linguistics, and art history" to bring a more concrete tale of the past.
He added that the site also contained some of the earliest known remains of horses found in Egypt.
The way volcanoes work!
Volcanic eruptions and formations are linked processes. Basically, a volcano is a portion of earth in which subterranean materials have made their way to the earth’s surface.
Humans live at the surface level of Earth, which is called the crust. Though the earth has many small layers, scientists call the first major area beneath the crust the mantle, and the area beneath the mantle the core. Magma, the main component in volcanoes, comes from the mantle region of the earth.
Volcanism is the process through which inner materials of the earth come up to the earth’s surface. It is also the process by which a planet cools itself.
There are three major ways in which volcanic activity can occur: spreading-center volcanism, subduction-zone volcanism, and hot-zone volcanism. All three types of volcanism are caused by the movement of tectonic plates.
In spreading-center volcanism, the tectonic plates move away from one another, forming an ocean or continental ridge. As the plates separate, the mantle rock flows up into the space created between them.
Here, the mantle rock melts to form magma, which emerges and forms a new crust. This process does not create a volcano as we know it, but it does patch up holes in the earth.
Most volcanoes are formed by subduction-zone volcanism. This process occurs when two tectonic plates collide and one plate from the lithosphere (the layer made up of the upper crust and the top layer of the mantle) is pushed deeper into the mantle, which forms a trench (usually located at the ocean floor). Most scientists believe that heat and pressure eject water from the lower plate (the subducting plate) into the upper plate.
Now that the upper plate contains more water, its melting point decreases and the upper plate melts into magma. The magma flows out and up because it is less dense than the surrounding rock. If under enough pressure, it spews through the surface. Otherwise, magma forms in a chamber beneath the earth’s crust.
Another way that volcanoes form is by hot-spot formation, which is not caused by shifting plates, but rather, by hotter, deeper magma rising from the lower to the upper mantle.
The hotter material from the lower mantle can then form an area just under the earth’s crust that is called a “hot spot.” No eruptions will occur at the surface, but as the plate above the hot spot shifts, a series of volcanoes forms. This is how the tropical vacation spot we know as Hawaii formed.
In both subduction-zone and hot-spot volcanism, magma always seeks lower pressure regions, so it rises toward the surface because it is less dense than the surrounding rock.
To form the conical shape of a volcano, one of two things happens: The magma pushes crust materials up around it, or magma spews forth and cools, collecting over time to form a mountain or hill, though it is possible to have a volcano in a crater or plateau.
The reason that magma does not always reach the surface immediately is because when the surrounding rock’s pressure exceeds the pressure of the liquid magma, it can keep this magma temporarily contained just beneath the earth’s surface.
Over time, the magma pressure can rise to exceed that of the surrounding rock, causing the molten rock and magma to spew forth through the surface.
Many dissolved gases exist in magma, and as long as the surrounding rock exerts a pressure greater than the gas vapors, the magma will remain contained. However, if the gas vapor pressure ever exceeds the pressure exerted by the rock, the dissolved gases expand and form bubbles called vesicles.
When vesicles form, one of two things happens: either the pressure of the surrounding rock decreases because of the decompression caused by the lowering pressure point of the magma, or the gas pressure increases because the cooling magma has crystallized and therefore enriched the gas inside it.
Magma filled with the tiny gas bubbles has a lower density than the surrounding bubble-free magma, and so the gas bubbles push the magma up and out of the volcano chamber.
The result is lava spewing out from a chamber just beneath the earth’s crust, thus forming the best-recognized version of the volcano.