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Lenticular clouds (Altocumulus lenticularis) are stationary lens-shaped clouds that form at high altitudes, normally aligned perpendicular to the wind direction. Due to their shape, they are often mistaken for Unidentified Flying Objects.
Where stable moist air flows over a mountain or a range of mountains, a series of large-scale standing waves may form on the downwind side. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds.
n 1883, an Indonesian volcano named Krakatoa exploded. Scientists liken the blast to a 100-megaton nuclear bomb. Fully 600 km away, people heard the noise as loud as a cannon shot. Plumes of ash rose to the very top of Earth's atmosphere. And the moon turned blue.
Other less potent volcanos have turned the moon blue, too. People saw blue moons in 1983, for instance, after the eruption of the El Chichon volcano in Mexico. And there are reports of some caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.
The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)--and no other sizes present. This is rare, but volcanoes sometimes spit out such clouds, as do forest fires.
Whether you use the newer definition or the one from the Maine Farmer’s Almanac, a blue moon, while not common, happens on a regular basis. Either way, they occur approximately 7 times in a 19 year period.
Much less common is a double blue moon (2 in one year). That only happens once in the same 19 year period. They occur in January and March, thanks to the short month, February. The last double we saw was in 1999. The next will happen in 2018.
Originally posted by cosmicexplorer
Originally posted by NoNameBrand
Another great post.
what that guy said
both posts are fun....and a few of those things i had never heard of....anyone got photos of the fire lightning....like lightning during a volcano?
Lightning can also occur within the ash clouds from volcanic eruptions, or can be caused by violent forest fires which generate sufficient dust to create a static charge.
How lightning initially forms is still a matter of debate. Scientists have studied root causes ranging from atmospheric perturbations (wind, humidity, friction, and atmospheric pressure) to the impact of solar wind and accumulation of charged solar particles. Ice inside a cloud is thought to be a key element in lightning development, and may cause a forcible separation of positive and negative charges within the cloud, thus assisting in the formation of lightning.
Volcano Lightning - Wiki
It comes as no shock that a potentially new type of volcanic lightning had long eluded scientists: The bolts can be as short as about 3 feet (1 meter) long and last just a few milliseconds.
But advanced instruments and a two-month heads-up allowed researchers to finally confirm the "teeny little sparks" during a recent eruption of Alaska's Redoubt Volcano. When Redoubt first began to rumble in late January 2009, volcanic seismologist Steve McNutt and colleagues scrambled to install various instruments near the volcano's vents.
Their quick efforts yielded unprecedented data when the mountain finally blew its top in March 2009.
McNutt, of the Alaska Volcano Observatory, had observed similar sparks during a 2006 eruption of Alaska's Augustine Volcano. The Redoubt Volcano data confirms the lightning's existence, he said.
The newfound bolts join two other types of volcanic lightning, McNutt said: Large, spectacular "natural fireworks" that sometimes accompany eruptions and an intermediate type, which shoots up from a volcano's vents and reaches a length of about 1.8 miles (3 kilometers).
Both types of bigger, more obvious bolts occur when water droplets and ice particles interact with the volcano's plume of electrically charged ash, creating a sort of "dirty thunderstorm," McNutt said.
It's unknown how the smaller sparks form, though one possibility is that electrically charged silica—an ingredient of magma—interacts with the atmosphere when it bursts out of Earth's crust, he said.
Still, it's hard to say if the sparks indeed represent a new type of lightning, noted Martin Uman, a lightning expert at the University of Florida in Gainesville. That's because lightning—basically any discharge of electricity—has no scientific definition.
No matter what you call them, the tiny sparks near volcanoes' vents may offer a safety benefit, added Uman, who was not involved in the Redoubt Volcano study.
When a volcano gives off a hint of an impending eruption—called a precursor event—scientists could set up instruments near the vents to detect sparks as an eruption begins, which would then alert officials even sooner, he said.
Such a warning could be critical for air traffic, since ash emitted by volcanoes is especially hazardous to jet engines.
There's also an aesthetic pleasure in watching lightning events: Any kind of volcanic lightning is just "supergorgeous," Uman said. "It's one of our best natural phenomena."
When it comes to volcanic eruptions, mile-high ash clouds and geysers of molten lava grab most of the attention.
But lightning often accompanies the blasts, and new research suggests that the electrical bolts may be part of a system dubbed a dirty thunderstorm.
Using radio waves to study the ash cloud, researchers have made some of the first direct observations of volcanic lightning. Their study reveals two distinct types of this poorly understood phenomenon and suggests it occurs due to "dirty thunderstorm" activity in the plume.
The study, to be reported tomorrow in the journal Science, describes some of the first direct observations made of volcanic lightning.
The findings offer a rare glimpse of this poorly understood phenomenon, including evidence of one type of lightning never seen before by scientists.
"It's the first real look at the details of at least one kind of volcano lightning—though of course every volcano might not be the same," said Martin Uman, co-director of the University of Florida Lightning Research program, who was not involved in the study.
The team behind the new research used radio waves to detect the previously unknown type of lightning as it flashed from the crater of Alaska's Mount Augustine volcano.
"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, an atmospheric physicist at the state engineering university New Mexico Tech.
"So 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 new evidence suggests that the eruption produced a large amount of electric charge.
"We're not sure if it comes out of the volcano or if it is created just afterwards. One of the things we have to find out is what's generating this charge," Thomas added.
The volcanic eruption itself is unable to generate sufficient electric charge to spark lightning for long after the eruption occurs or far from the crater, the researchers said.
Instead the scientists believe that electric charges are generated when rock fragments, ash, and ice particles in the plume collide to produce static charges—in much the same way that ice particles collide to create charge in regular thunderstorms.
"As the plume started going downwind, it seemed to have a life of its own and produced some 300 more or less normal [lightning bolts]," the University of Florida's Uman said.
"The implication is that it has produced more charge than it started with. Otherwise [the plume] couldn't continue to make lightning."
In a scene no human could have witnessed, an apocalyptic agglommeration of lightning bolts illuminates an ash cloud above Chile's Puyehue volcano on Sunday.
The minutes-long exposure shows individual bolts as if they'd all occurred at the same moment and, due to the Earth's rotation, renders stars (left) as streaks. Lightning to the right of the ash cloud appears to have illuminated nearby clouds—hence the apparent absence of stars on that side of the picture.
After an ominous series of earthquakes Saturday morning, the volcano erupted that afternoon, convincing authorities to evacuate some 3,500 area residents. Eruptions over the course of the weekend resulted in heavy ashfalls, including in Argentine towns 60 miles (a hundred kilometers) away.
Flames reach up to the heavens as lightning flashes criss-cross the sky.
These extraordinary images show the full force of Mother Nature as a Chilean volcano erupts for the first time in 50 years.
Ash has been thrown six miles up into the sky and the South American government has ordered the evacuation of thousands of residents.
Winds fanned the ash toward neighbouring Argentina, darkening the sky in the ski resort city of San Carlos de Bariloche, in the centre of the country, and its airport has also been closed.
A volcanic lightning storm isn't "unlike a regular old thunderstorm," Martin Uman, a lightning expert at the University of Florida in Gainesville, told National Geographic News in 2010.
The same ingredients are present: water droplets, ice, and possibly hail—all interacting with each other and with particles, in this case ash from the eruptions, to cause electrical charging, Uman said.
The eruption in the Puyehue-Cordon Caulle volcanic chain, about 575 miles south of the capital, Santiago, also prompted authorities to close a busy border crossing into Argentina.
It was not immediately clear which of the chain's four volcanoes had erupted because of ash cover and weather conditions. The chain last saw a major eruption in 1960.
Local media said the smell of sulphur hung in the air and there was constant seismic activity.
'The Cordon Caulle (volcanic range) has entered an eruptive process, with an explosion resulting in a 10-kilometre-high gas column,' the state emergency office ONEMI said.
This development is the latest volcanic activity to affect the country. Three years ago, Chile's Chaiten volcano erupted spectacularly for the first time in thousands of years, spewing molten rock and a vast cloud of ash that reached the stratosphere and was visible from space.
It also drifted over neighbouring Argentina, coating towns. Chile's Llaima volcano, one of South America's most active, also erupted that year and again in 2009.
It was the latest in a series of volcanic eruptions in Chile in recent years. Chile's Chaiten volcano erupted spectacularly in 2008 for the first time in thousands of years, spewing molten rock and a vast cloud of ash that reached the stratosphere.
The ash also swelled a nearby river and ravaged a nearby town of the same name.
The ash cloud from Chaiten coated towns in Argentina and was visible from space. Chile's Llaima volcano, one of South America's most active, erupted in 2008 and 2009.
Chile's chain of about 2,000 volcanoes is the world's second largest after Indonesia. Some 50 to 60 are on record as having erupted, and 500 are potentially active.
Read more: Chaiten
Even so, danger remains. In a statement on website of the regional government of Los Rios, Chile, for example, Governor Juan Andrés Varas warned that ash and potentially poisonous volcanic gases are slowly rolling toward a nearby valley.
"Fortunately, the valley doesn't drop abruptly, so we have time to evacuate," Varas was quoted as saying by CNN.