۱۳۹۰ تیر ۹, پنجشنبه

آیا آدمی بیش از آتشفشان ها گاز اکسید کربن تولید می کند؟ Do Humans Produce More CO2 Than Volcanoes


Volcanoes are spectacular displays of the massive forces at work inside our planet, yet they are dwarfed by humans in at least one respect: their carbon dioxide emissions.
Despite statements made by climate change deniers, volcanoes release a tiny fraction of the amount of carbon dioxide emitted by human activities every year.
In fact, humans release roughly 135 times more carbon dioxide annually than volcanoes do, on average, according a new analysis. Put another way, humans emit in under three days the amount that volcanoes typically release in a year, according to the best estimates of volcanic emissions.
"The question of whether or not volcanoes emit more CO2 than human activity is one I get more than any question in my email from the general public," says Dr Terrence Gerlach, a retired volcanologist, formerly with the Cascades Volcano Observatory, part of the US Geological Survey. Even Earth scientists who work in other areas often pose him the question, he says.
To lay out a clear answer, Gerlach compiled the available estimates of CO2 emissions from all global volcanic activity on land and undersea and compared them with estimates for human emissions. He published the compilation in Eos, a publication of the American Geophysical Union.
Researchers estimate the amounts of carbon dioxide released by terrestrial volcanic eruptions by methods including remote sensing or flying through clouds of erupting volcanic gas, and by measuring certain isotope concentrations near undersea volcanoes. Carbon dioxide is dissolved in magma at great depths and is released as the magma rises to the surface.
"A lot of climate sceptics claim that volcanoes emit more CO2 than humans do," says Gerlach. "They never give any numbers, but the fact is you will never be able to find the volcanic gas scientist that will agree to that."
One example of these sceptic's claims is the 2009 book, Heaven and Earth: Global Warming, the Missing Science by Professor Ian Plimer of the University of Adelaide, who did not respond to Discovery News' requests for comment.
"The main reason, I think, that this myth persists," says Gerlach: "First of all, the emissions are extremely spectacular. When people see volcanic eruptions on television and it's awesome, and it's very easy for people to imagine that huge amounts of CO2 are being emitted to the atmosphere."
"However, these spectacular volcanic explosions that are so stunning on TV last only a few hours," he says. "They are ephemeral. In contrast, the sources of anthropogenic CO2 (smokestacks, exhaust pipes, etc) are comparatively unspectacular, commonplace, and familiar, and in addition they are ubiquitous, ceaseless, and relentless. They emit CO2 24/7."

آتشفشان ها در زیر پهنه های یخ در ایسلند، کا نادا و امریکا Volcanoes Under Glaciers in Iceland, Canada and the United States



آتشفشان ها در زیر پهنه های یخ در ایسلند، کا نادا و امریکا
The combination of hot rock and ice produce a unique set of hazards.

Where Fire and Ice Meet


Glaciovolcanoes, they're called, these rumbling mountains where the orange-red fire of magma meets the frozen blue of glaciers.

Eyjafjallajökull is One of Many Glaciovolcanoes


Iceland's Eyjafjallajökull volcano, which erupted recently, is but one of these volcanoes. Others, such as Katla, Hekla and Askja in Iceland; Edziza in British Columbia, Canada; and Mount Rainier and Mount Redoubt in the U.S., are also glaciovolcanoes: volcanoes covered by ice.

Meltwater Floods - Jökulhlaups


"When an ice-covered volcano erupts, the interplay among molten magma, ice and meltwater can have catastrophic results," says Sonia Esperanca, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funds research on glaciovolcanoes.

In Iceland, scientists were well prepared for the floods, called "jökulhlaups," that can happen after a glaciovolcano blows and melts its glacial covering. The floods were followed by tons of ash ejected into the atmosphere.

The Impact on Air Transportation



Most of the rest of the world, however, was unaware that an eruption from a small, northern island in the middle of the Atlantic Ocean could freeze air transportation and stop global commerce in its tracks.

That, say NSF-funded scientists Ben Edwards at Dickinson College and Ian Skilling at the University of Pittsburgh, is the nature of glaciovolcanoes.

Understanding volcano-ice interactions occupies much of Edwards' and Skilling's daily lives.

They're working at Mt. Edziza in British Columbia, Canada, and in Iceland to find out how glaciovolcanic deposits--rock fragments strewn for miles after an ice-covered volcano erupts--are formed.

Volcano-ice interaction presents unique types of hazards, say the geologists, but what's left behind after an eruption can also serve as a window into our geologic past.

 

فوران آتشفشان در شیلی Puyehue-Cordón Caulle


The eruption at Chile’s Puyehue-Cordón Caulle Volcanic Complex continued in late June 2011, with lava and ash still pouring out 23 days after the eruption began.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the Terra satellite captured this nighttime view of the volcanic complex on June 27, 2011. In this thermal infrared image, hot areas are bright and cold areas are dark. The white feature in the center of the image is an active lava flow.
According to SERNAGEOMIN, Chile’s ministry of mining and geology, the eruption has been subsiding a bit, with fewer and lower intensity tremors and earthquakes. Ashfalls, lahars, and landslides are the primary threat at the moment.
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آتش سوزی " نیو مکزیکو" از فضا New Mexico Wildfire from Space


A crew member aboard the International Space Station, flying at an altitude of approximately 235 statute miles on June 27, 2011, exposed this still photograph of a major fire in the Jemez Mountains of the Santa Fe National Forest in north-central New Mexico.” Quoted from the NASA image release.

انرژی زمین گرمایی از آتشفشان " کرافتلا " در ایسلند Geothermal Energy from Krafla Volcano, Iceland





Geologists drilling an exploratory geothermal well in 2009 in the Krafla volcano in Iceland met with a big surprise: underground lava, also called magma, flowed into the well at 2.1 kilometers (6,900 feet) depth.

It forced the scientists to stop drilling.

"To the best of our knowledge, only one previous instance has been documented of magma flowing into a geothermal well while drilling," said Wilfred Elders, a geologist at the University of California, Riverside, who led the research team

Fluids at Supercritical Pressures & Temperatures
جریان گدازه ناشی از فشار و گرمای بیش از اندازه ی خطرنا ک
Elders and his team studied the well within the Krafla caldera as part of the Iceland Deep Drilling Project, an industry-government consortium, to test whether geothermal fluids at supercritical pressures and temperatures could be exploited as sources of power, said Leonard Johnson, program director in NSF's Division of Earth Sciences, which funded the research.

"We were drilling a well designed to search for very deep--4.5 kilometers (15,000 feet)--geothermal resources in the volcano," said Elders. "While the magma flow interrupted our project, it gave us a unique opportunity to test a very hot geothermal system as an energy source."
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