Fire Crews Continue to Battle Rim Fire: Photos

Fire crews continue to battle the "Rim Fire" inferno 

raging just to the west of Yosemite Park. Extremely dry 

forests surrounding the blaze, high winds and potential 

for the fire to jump from one location to another over 

long distances makes for extremely difficult firefighting 

conditions.

The plume of carbon monoxide pollution from the Rim 

Fire burning in and near Yosemite National Park, Calif., is 
visible in this Aug. 26, 2013 image from the Atmospheric 

Infrared Sounder (AIRS) instrument on NASA’s Aqua 

spacecr
v

A MAFFS C-130 drops fire retardant along a fire break 

just east of Tuolumne City Ca.

View from Greeley Hill of the Rim Fire backing down 

Pilot 

Ridge at 1:00 am on Aug. 26.

Ebbetts Pass and Calaveras County firefighters watch

 back fire operations on Evergreen Road.


The Berkeley Tuolumne Family Camp, a city-owned 

camp 

that has operated since 1922, burned in the Rim Fire.


A fire-charred and melted power meter.


Burned outbuilding and pickup truck.


A highway sign burned by the Rim Fire, is seen in

 Yosemite National Park, California, August 24, 2013.


Big Bear firefighter JON CURTIS keeps a close eye on a

 'slop over' fire that jumped Hwy 120 just east of Hardin 

Flat Road while fighting the Rim Fire on Aug. 25.



The National Park Service (NPS) fire crew is helping to 

protect the Giant Sequoias in Tuolumne Grove, about 16 

miles (26 km) west of Yosemite Village on Tioga Pass 

Road in Yosemite National Park.


Majestic Giant Sequoias tower over NPS fire crews as 

they establish a hand line, the term for a fire line made 

from hand tools, in the Merced and Tuolumne Groves.


NPS crews lay a sprinkler hose along their hand line as 

part of a multi-pronged approach to protecting the Giant 

Sequoias against the Rim fire.


Sprinklers are placed around the perimeter of the 

Merced 

and Tuolumne Groves of Giant Sequoias in an effort to 

protect the big trees.


Smoke from the Rim Fire hovers over the Groveland 

Ranger Station.

Satellite images of the fire taken at night show the

 progression of flames as it expanded into Yosemite 

National Park.

Fire fighters on Aug. 24, worked to protect Tuolumne

 City and the populated Highway 108 corridor from the

 western edge of the fire. They were also able to

 maintain the eastern edge of the fire from spreading 

into Yosemite National Park, but the fire grew in the 

southeast and then penetrated the eastern lines on Aug

. 25, becoming extremely active on the east as of Aug. 26.

This image shows the fire on the night of Aug. 26. NBC4 

in Southern California reports: "California fire officials 

say the fire is so large and is burning with such a force, it

 has created its own weather pattern, making it difficult 

to predict which direction it will move. 'As the smoke

 column builds up it breaks down and collapses inside of 

itself, sending downdrafts and gusts that can go in any 

direction,'" CalFire spokesman Daniel Berlant told the

 Associated Press. "There's a lot of potential for this one 

to continue to grow.'

This natural-color satellite image was collected by the

 Moderate Resolution Imaging Spectroradiometer (MODIS)

 aboard the Terra satellite on August 25, 2013. Actively 

burning areas, detected by MODIS’s thermal bands, are

 outlined in red.

A close-up of the previous image. "The San Francisco 

water and power utility said the city has not so far seen

 any interruptions in service, though two hydroelectric 

plants have sustained damage in the fire," reported the 

AFP. "Crews were working on repairing one of the plants,

the utility said on its website, and supplemental power 

supplies in the interim have cost some $600,000."

Smoke from the Rim Fire drifts over Yosemite.

More than 4,081 firefighters, supported by helicopters 

and DC-10 air tankers, are working to slow the spread of 

the Rim Fire, which started on August 17 from causes still

 under investigation. So far the fire is 20 percent 

contained.

Chasing Red Sprites and Blue Jets: Photos

Jason Ahrns, a graduate student at the University of 

Alaska-Fairbanks, goes sprite-chasing at night during 

electrical storms. Here he captures column-shaped red 

sprites over Red Willow County, Nebraska, on Aug. 12, 

2013.

 “jellyfish” sprite photographed over Republic County, 

Kansas, on August 3, 2013. "I have very good low light 

eyesight, and I've watched tons of sprites in real time on 

the context cameras so I know exactly what and where 

to look. I was watching intently out the window while I 

snapped these shots, and the camera caught a sprite that

 I didn't see," writes Ahrns in his blog: 

http://musubk.blogspot.fr/2013/08/sprites-2013-update-

4.html

Like flames from a butane lighter, three blue jets 

(slightly blurred due to the motion of the aircraft) 

appear 

above the lightning-lit clouds in this photo taken over 

Republic County, Kansas, on August 3, 2013. Ahrns 

describes this picture as the "the cream of the crop," due 

to the difficult nature of capturing blue jets. "Since jets 

tend to hug the top of the clouds it's understandable 

that 

they're more difficult for a ground observer to 

see/photograph, so it makes sense that being up in a 

sprite-chasing aircraft would give me a serious

 advantage," he writes. "Unlike sprites, blue jets aren’t 

directly triggered by lightning, but seem to be somehow 

related to the presence of hail storms," reports the 

Smithsonian:

 http://blogs.smithsonianmag.com/artscience/2013/08/sci


entists-capture-rare-photographs-of-red-

Red sprite over Canadian County, Oklahoma, on August 

6, 2013. "I was also able to see quite a few jets with my 

naked eyes! That's a first for me, and I'm always excited 

to see a new sky phenomenon for myself. I still haven't 

been able to see a sprite naked-eye, and it impresses me 

just how difficult that actually is," Ahrns writes

Ahrns' Nikon D7000 on a flexible tripod points out the 

window of the sprite-chasing aircraft, a Gulfstream V 

with the National Center for Atmospheric Research. "I 

butted the camera up against the window glass and put 

my weight on it to get rid of most of the wobbles and 

light leaks, but the motion of the aircraft itself still 

showed up, especially when we hit a patch of turbulence 

(we are, you know, flying right next to a 

thunderstorm)," 

he writes.

Ahrns' high-speed video set-up next to the window of 

the 

Gulfstream V.

Sprites over Red Willow County, Nebraska, 

photographed 

on Aug. 12, 2013.

Sprites over Red Willow County, Nebraska, 

photographed 

on Aug. 12, 2013.

Thousands Flee Erupting Indonesia Volcano

vLightning strikes as Mount Sinabung volcano spews ash 

and hot lava, at Simpang Empat village in Karo district, 

Indonesia's North Sumatra province.

A volcano in western Indonesia has erupted eight times in

just a few hours, "raining down rocks" over a large area 

and forcing thousands to flee their homes, officials said 

Sunday.

Mount Sinabung has been erupting on and off since 

September, but went into overdrive late Saturday and 

early Sunday, repeatedly spewing out red-hot ash and

 rocks up to eight kilometers (five miles) into the air.

Several thousand people left their homes overnight, 

taking the total number of those who have fled since the 

volcano rumbled to life to around 12,300, said the national disaster agency.

"People panicked last night as the eruption was accompanied by a loud thunderous sound and vibrations. Then it started raining down rocks," said local government official Robert Peranginangin.

"They ran helter-skelter out of their homes and cried for help."

He added there were no known casualties from the latest eruptions.

The volcanology agency raised the alert level for the 

volcano, on the northern tip of Sumatra island, to the 


highest point on a four-stage scale, meaning a hazardous 

eruption is imminent or under way.

National disaster agency spokesman Sutopo Purwo 

Nugroho said the government was calling for people 

living 

within five kilometers (3.1 miles) of the volcano to leave 

their homes.

Sinabung, one of dozens of active volcanoes in Indonesia 

which straddles major tectonic fault lines known as the 

"Ring of Fire", erupted in September for the first time 

since 2010.

In August five people were killed and hundreds 

evacuated when a volcano on a tiny island in East Nusa 

Tenggara province erupted.

The country's most active volcano, Mount Merapi in 

central Java, killed more than 350 people in a series of 

violent eruptions in 2010.

v

Volcanic Lava Viewed from Space

Erupting volcanoes are best viewed from a distance, as the recent deadly tragedy on Mount Mayon in the Philippines proves. In the case of Paluweh volcano, the ideal spot to see the eruption was from 705 kilometers (438 miles) above the Earth.

On April 29, the Landsat Data Continuity Mission satellite orbited over Indonesia’s Flores Sea and snapped shots of Paluweh, a volcanic island. Smoke and ash drifted far out to sea from the 5-mile-wide-island. The billowing ash hid the lava flowing from the heart of the volcano.

A thermal imaging camera on the satellite allowed NASA and U.S Geological Survey scientists to safely peek beneath the volcanic cloud at the glow of lava spewing from the volcano.

The satellite’s Thermal Infrared Sensor (TIRS) peered beneath the plume. NASA engineers had configured the sensor to distinguish the actual lava hotspot from the radiant heat it produced. The satellite could detected differences in temperature as small as one-tenth of a degree Celsius. This allowed scientists to accurately view the lava flow from the safety of a control room.

“We can image the white, representing the very hot lava, and right next to it we image the gray and black from the cooler surrounding ash,” said Betsy Forsbacka, TIRS instrument manager at NASA’s Goddard Space Flight Center in a press release. “It’s exciting that we’re imaging such diverse thermal activity so well.”

IMAGE 1: An ash plume drifts from Paluweh volcano in Indonesia in this image, taken April 29, 2013 from the Landsat Data Continuity Misison’s Operational Land Imager instrument.

(Robert Simmon, NASA’s Earth Observatory, using data from USGS and NASA)

IMAGE 2: A bright white hot spot, surrounded by cooler dark ash clouds, shows the volcanic activity at Paluweh volcano in the Flores Sea, Indonesia. This thermal image was taken by the Landsat Data Continuity Mission’s Thermal Infrared Sensor on April 29, 2013.

EARTH

Giant Underwater Volcano Discovered in Indonesia

The deep ocean has many secrets, and scientists aboard the Okeanos Explorer just discovered a big one – an enormous volcano looming 7,000 feet below the ocean’s surface off the coast of Indonesia.

Exposing Kawio Barat volcano is the first major discovery of theIndonesia-USA Deep-Sea Exploration of the Sangihe Talaud Region (INDEX 2010) mission, which started in June and runs until August 14.

This region was selected for exploration based on prior surveying conducted by Indonesian and Australian scientists in 2004. The earlier work revealed hot spots, but limited instrumentation could not reveal the source of the anomalies.

Okeanos Explorer, the National Oceanic and Atmospheric Administration (NOAA) ship used for the INDEX 2010 mission, provided the magic touch to unveiling the volcano. Equipped with a built-in multibeam sonar and a remote operating vehicle (ROV) nicknamed "Little Hercules," this bad boy covered every inch of the 10,000-foot-tall volcano, top to bottom.

Eruption of Iceland's Grimsvotn Volcano : Photos

The initial eruption of Grímsvötn on May 21, 2011,

 reached 20 kilometers (12 miles) high, more than 

twice the height of last year's eruption of 

Eyjafjallajökull, which only reached 8 kilometers (

5 miles). The material spewed from Grímsvötn however 

is coarser and heavier and not expected to remain aloft 

for as long or as far. This image shows the plume as the 

volcano continued to erupt on May 23.

The eruption of the Grímsvötn volcano sent thousands 

of tonnes of volcanic ash into the sky on May 23, 2011, 

above Iceland. During the peak of the eruption, 

Grímsvötn produced 1,000 times as many lightning 

strikes per hour as Eyjafjallajökull had a year earlier.

This image shows the plume as Grímsvötn continued 

to erupt on May 23.

Mammatus clouds are seen above the plume as the 

eruption of Grímsvötn continued on May 23, sending 

thousands of tonnes of volcanic ash into the sky above 

Iceland.

The MODIS instrument on NASA's Terra satellite captured 

this natural-color image of the Grímsvötn volcano 

eruption in Iceland on May 22, 2011, at 05:15 UTC (5:00 

a.m. local time).

NASA's Earth Observatory reports that "above 

Grímsvötn’s summit, volcanic ash forms a circular 

brown plume that towers above the surrounding 

clouds. In the southeast, ash has colored the snow 

surface dark brown. Ash from the volcano reduced 

visibility to about 50 meters (160 feet) in some places."

The MODIS instrument on NASA's Terra satellite captured 

this natural-color image of the Grímsvötn volcano 

eruption in Iceland on May 22, 2011, at 13:00 UTC (1:00 

p.m. local time)

Contrails over Buckingham Palace during the meeting of 

President Obama with the Royal family on Tuesday 

provided visible signs that the ash from Iceland's 


Grímsvötn volcano is proving far less disruptive than last 

year's eruption of Eyjafjallajökull. Even so, hundreds of 

flights have been canceled leaving thousands of 

passengers in airline limbo.

To avoid the oncoming plume, Monday night President 

Obama left Ireland aboard Air Force One for London 

earlier than planned. He is scheduled to visit Poland and 

attend the G8 meeting in Deauville, France, before 

returning to the United States. On Sunday he will meet 

with residents of the tornado-struck city of Joplin, Mo.

Four Dead as Philippine Volcano Erupts

The Mayon volcano as seen from a plane in Legaspi City, Albay province on May 3, 2010.

Three German tourists and their Filipino tour guide were crushed to death when one of the Philippines' most active volcanoes spewed a giant ash cloud and a hail of rocks on Tuesday, authorities said.

Up to 20 foreigners and their guides were on the slopes of picturesque Mount Mayon when it erupted without warning, and rescue workers had been dispatched on helicopters to search for survivors, officials and a tour operator said.

"It rained like hell with stones," local tour operator Marti Calleja quoted an Austrian woman who survived the ordeal as saying.

"The rocks that came crashing down on them were as big as dining (table) sets," he told AFP by phone.

Calleja said three Filipino guides from his firm and five foreigners had begun hiking up Mayon just a few hours before the eruption, which sent a thick column of ash 500 metres (1,600 feet) into the air.

Three Germans and one of the guides from his group were killed, while the Austrian woman suffered minor bruises, according to Calleja.

Regional police spokesman Superintendent Renato Bataller confirmed the four fatalities, with seven others injured including four Thais.

Calleja said the foreigners paid about $100 each for an overnight adventure on the 2,460-meter (8,070-foot) Mayon, which is famed for its near-perfect cone but has a long history of deadly eruptions.

A six-kilometer (3.7-mile) radius "permanent danger zone" is supposed to be enforced around the volcano. But Calleja said the local government allowed people to climb when there were no signs of an eruption.

"Between 300 and 1,000 climbers go here during the peak season from May to August," Calleja said.

Volcanologists described the eruption as a 73-second "steam-driven minor explosion" that was not expected to be repeated anytime soon.

Chief state seismologist Renato Solidum said people living around Mayon did not need to evacuate. He said the explosion was triggered when rainwater made contact with hot ash deposits on the crater mouth.

"There is no magma activity. Essentially what happened today is a normal process of a steam-driven explosion," Solidum told a news conference in Manila.

Residents in towns around the picturesque volcano said they were surprised by the sudden activity, which came as many were having breakfast.

"It was so sudden that many of us panicked," Jun Marana, a 46-year-old bus driver and father of two, told AFP by telephone.

"When we stepped out we saw this huge column against the blue sky."

Marana said the ash column was dispersed by winds after about an hour, but said he was not taking his chances and was prepared to leave his home anytime.

Mayon, about 330 kilometers (200 miles) southeast of Manila, has erupted dozens of times in recorded history.

In 1814, more than 1,200 people were killed when lava flows buried the town of Cagsawa. In December 2009 tens of thousands of villagers were displaced when Mayon spewed ash and lava.

The volcano also erupted in August 2006. There were no direct deaths caused by the explosion, but the following December a passing typhoon unleashed an avalanche of volcanic mud from its slopes that killed 1,000 people.

Helium Gas As Volcano Detector

NASA's Earth Observing-1 (EO-1) satellite snapped this 

image of the submarine eruption off El Hierro Island, one 

of the Canary Islands, on Feb. 10, 2012.

As the volcanic island of El Hierro, the smallest of Spain's

 Canary Islands, rumbled and groaned over the course of 

seven months in 2011 and 2012, gases silently 

percolated 
up through the island's soil and groundwater.

Eventually, a spectacular plume appeared off the 

southern coast of the island, a sign that El Hierro 

volcano, an underwater volcano just offshore, had finally 
erupted.

During that time, researchers had been busy collecting 

and analyzing the helium gas content of more than 8,000 

soil and water samples. Now, those data can be used to 

monitor El Hierro and forecast its next eruption, 

researchers say, and likely other volcanic eruptions 

around the globe as well.

"We believe that helium can anticipate the detection of 

magmatic movement even before those movements can 

be detected by seismic activity," said Eleazar Padrón, a 

geochemist at Spain's Technological Institute for the 

Renewable Energies, who led the work.

ANALYSIS: The Fallout of a Helium-3 Crisis

An almost ideal gas

Researchers have been using gas emissions to forecast 

volcanic eruptions for at least 30 years, but they usually 

focus on carbon dioxide, the second most abundant gas 

(after water vapor) in volcanic eruptions. Helium, a 

noble gas, is a better candidate for tracking and

 forecasting eruptions, Padrón explained, because it 

doesn't react with rocks or groundwater and 

microorganisms don't consume or produce helium.

"Because of these properties, helium has been 

considered 
by geochemists as an almost ideal geochemical 

indicator," 

he told OurAmazingPlanet.

Padrón and his team found that measuring the flow of 

helium in El Hierro island's soil and water gave them 

clues as to when magma under the island was moving and 
how close it was to the surface — both important factors 

in forecasting a volcanic eruption.

The team also measured two helium isotopes — atoms of 

the same element with different numbers of neutrons. 

Helium-3, for example, has one neutron, whereas 

helium-4 has two. Helium-4 is produced when radioactive 
elements decay in the Earth's crust (its outermost layer), 

but helium-3, which accounts for the bulk of Earth's 

helium, is primarily found in the mantle (the hot layer 

between the crust and core).

Looking at the proportions of helium-3 and helium-4 in a 

gas sample, the researchers could determine how much 

helium had come straight from the mantle, and how 

much came from fresh breaks and fractures in the crust 

below El Hierro island. Fracturing crust is another clue 

that a volcanic eruption could be imminent.

The team's analyses show that, as the volcano began to 

stir, the crust fractured and helium, mostly from the 

mantle, flowed to the surface. As the actual eruption 

began, gas flow at the surface increased dramatically, 

and gas pressure beneath the island dropped. Then as 

seismic activity at El Hierro picked up again, the crust 

fractured and deformed extensively, and helium-4 

became a larger component of the total helium released 

on the island.

NEWS: The Volcanoes Are Alive with the Sound of Magma

A starting point

The system Padrón's team used to track helium at El 

Hierro may be a good example for researchers seeking to

 monitor other active volcanoes.

"This is a starting point for developing continuous 

monitoring stations of diffuse helium flux to strengthen 

the volcanic surveillance program at many volcanoes 

worldwide," Padrón said.

One reason this method proved important for 

forecasting 

activity at El Hierro volcano was that magma migrated to

 the surface aseismically — basically silently, without 

significant earthquakes to herald its arrival. The eruption 
could have taken residents by surprise if scientists hadn't 

been tuned into the island's increasing gas emissions.

Lagging technology will be the biggest challenge in 

setting up helium monitoring systems, Padrón said. To 

date, there's no instrument that can continuously 

quantify the type of diffuse helium fluxes seen at El 

Hierro.

The Volcanoes Are Alive with the Sound of Magma

Piton de la Fournaise volcano crater on Reunion Island (Indian Ocean, France)

THE GIST

- Geophysicists found they could map the course of an eruption by matching gas sounds in a volcano's magma chamber to gas flow out of vents.

- When the vents stop emmiting gasses the eruption is over.

When volcanoes erupt, they create a stunning visual 

spectacle for anyone watching, but they also emit impressive noises that range from low rumbles to concussive blasts. Some of the sounds are below the range of human hearing, and a new study suggests they can be used to better understand and monitor eruptions.

Geophysicist Aurélien Dupont of the Pusan National University in South Korea studied the low-frequency sounds made by gases percolating through basaltic magma, a type of magma that flows easily because it has a low viscosity (or, roughly, thickness) and gas content. Volcanoes that spew basaltic lava tend to have gentle slopes, making impressive eruptive displays of rivers of lava running down their sides.

As the magma travels from the volcano's underground magma chamber, pockets of gas trapped inside it expand (and produce the low-frequency sound, or infrasound) until they reach the surface, where the gas can bubble away into the atmosphere.

Dupont and his colleagues used condenser microphones and microbarometers to track the underground sounds of Piton de la Fournaise volcano on Reunion Island in the Indian Ocean between 1992 and 2008. They found they could match the sounds produced by the gas to its flow out of vents in and around the volcano crater, and map the course of the eruption.

"If no volcanic gas escapes anymore from the vents, detections stop and the eruption is over. Infrasound can accurately characterize the beginning and the end of an eruption," Dupont said in a statement.

The research, to be presented in Hong Kong at a joint meeting of the Acoustical Society of America, the Acoustical Society of China, the Western Pacific Acoustics Conference, and the Hong Kong Institute of Acoustics, shows that infrasound is another tool that can be used to probe volcanic eruptions, the scientists say.

"The quantitative analysis of the noise produced by the gas flow allows us not only to understand a natural system as complex as a volcano but allows us also to better monitor it," Dupont said.

Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Volcanic Lightning: How does it work?!

Volcanic lightning strikes during an eruption of Japan's Sakurajima volcano in February 2013.

The fusion of flash with ash! Say the words aloud, together, and it sounds impossible – the kind of thing a six-year-old might think up. And yet, volcanic lightning is very real. But how does it happen?

Few phenomena can compete with the raw beauty and devastating power of a raging thunderstorm, save for a particularly violent volcanic eruption. But when these two forces of nature collide, the resulting spectacle can be so sublime as to defy reason.

The photograph above offers some important insights into the formation and study of volcanic lightning. It was taken late last month by German photographer Martin Rietze, on a visit to Japan's Sakurajima volcano. Only very big eruptions, he tells us via email, can generate major thunderbolts like the ones seen above.

PHOTOS: Eruption of Iceland's Grimsvotn Volcano

Smaller eruptions tend to be accompanied by more diminutive storms, which can be difficult to spot through thick clouds of ash. What's more, lightning activity is highest during the beginning stages of an eruption, making it all the more challenging to capture on film. Photographing a big volcanic event at any stage is hard enough as it is; if you're not nearby when it happens, says Rietze, "you will always arrive too late."

It turns out the same things that make volcanic lightning hard to photograph also make it difficult to study. The first organized attempt at scientific observation was made during Iceland's Surtsey eruption in 1963 (pictured here). The investigation was later recounted in a May 1965 issue of Science:

"Measurements of atmospheric electricity and visual and photographic observations lead us to believe that the electrical activity is caused by the ejection from the volcano into the atmosphere of material carrying a large positive charge."

Translation? Volcanic lightning, the researchers hypothesize, is the result of charge-separation. As positively charged ejecta makes its way skyward, regions of opposite but separated electrical charges take shape. A lightning bolt is nature's way of balancing the charge distribution. The same thing is thought to happen in regular-old thunderstorms. But this much is obvious, right? So what makes volcanic lightning different?

Close to 50 years have transpired since Surtsey exploded in November 1963. Since then, only a few studies have managed to make meaningful observations of volcanic eruptions. One of the most significant was published in 2007, after researchers used radio waves to detect a previously unknown type of lightning zapping from the crater of Alaska's Mount Augustine volcano in 2006.

"During the eruption, there were lots of small lightning (bolts) or big sparks that probably came from the mouth of the crater and entered the (ash) column coming out of the volcano," said study co-author Ronald J. Thomas in a 2007 interview with National Geographic. "We saw a lot of electrical activity during the eruption and even some small flashes going from the top of the volcano up into the cloud. That hasn't been noticed before."

The observations suggest that the eruption produced a large amount of electric charge, corroborating the 1963 hypothesis – but the newly identified lightning posed an interesting puzzle: where, exactly, do these charges come from? "We're not sure if it comes out of the volcano or if it is created just afterwards," Thomas explains. "One of the things we have to find out is what's generating this charge."

Since 2007, a small handful of studies have led to the conclusion that there exist at least two types of volcanic lightning – one that occurs at the mouth of an erupting volcano, and a second that dances around in the heights of a towering plume (an example of the latter occurred in 2011 above Chile's Puyehue-Cordón Caulle volcanic complex, as pictured here. (Photograph by Carlos Gutierrez/Reuters.) Findings published in a 2012 article in the geophysics journal Eos reveal that the largest volcanic storms can rival the intensity of massive supercell thunderstorms common to the American midwest. Still, the source of the charge responsible for this humbling phenomenon remains hotly debated.

One hypothesis, floated by Thomas' team in 2007, suggests that magma, rock and volcanic ash, jettisoned during an eruption, are themselves electrically charged by some previous, unknown process, generating flashes of electricity near the volcano's opening. Another holds that highly energized air and gas, upon colliding with cooler particles in the atmosphere, generate branched lightning high above the volcano's peak. Other hypotheses, still, implicate rising water and ice-coated ash particles.

"What is mostly agreed upon," writes geologist Brentwood Higman at Geology.com, "is that the process starts when particles separate, either after a collision or when a larger particle breaks in two. Then some difference in the aerodynamics of these particles causes the positively charged particles to be systematically separated from the negatively charged particles." You can see the diagram here.

The exciting thing about this process is that these differences in aerodynamics, combined with various potential sources of charge (magma, volcanic ash, etc) suggest that there may actually be types of volcanic lightning we've yet to observe. As Martin Uman, co-director of the University of Florida Lightning Research program, told NatGeo back in 2007: "every volcano might not be the same."

http://news.discovery.com

Share this article :

Share on FB Tweet Share on G+ Submit to Digg