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Mount Pelee, on the island of Martinique in the Caribbean is one of those volcanoes with such a famous and devastating eruption, that a whole class of eruptions has been named after it. In 1902, it was the source of the worst volcanic disaster of the 20th century when a pyroclastic flow blasted down its flanks and killed more than 30,000 people destroying the town of Saint-Pierre.
The volcano has an elevation of 1,397 meters, and is part of a chain of volcanoes that stretch from Puerto Rico to Venezuela. This is the point where the Caribbean Plate Meets the Atlantic Oceanic crust belonging to the South American Plate. With all this tectonic action, there are many active volcanoes in the region. Mount Pelee is a common stratovolcano, composted of many layers of lava flows and fragmented volcanic debris. The current cone formed in the last 3000 years after a previous cone collapsed in an eruption similar to Mount St. Helens.
Inhabitants of Martinique could see evidence that Mount Pelee was awakening in 1900 when activity on the volcano increased. There were relatively minor steam eruptions, and there were several minor blasts of cinders and ash. There were several larger eruptions, but these were just setting the stage for the big eruption on May 8, 1902. Observers saw the side of Mount Pelee detonate, with a dense black cloud of ash shooting out horizontally. This sent a pyroclastic flow down the slopes of the volcano, reaching and destroying the town of Saint-Pierre within a minute.
Vulcanologists have named an entire class of eruptions after what happened on Mount Pelee. Pelean eruptions describe when a volcano has a horizontal explosion on its flanks, sending out pyroclastic flows. They’re some of the most dangerous eruptions in the world.
We have written many articles about volcanoes for Universe Today. Here’s an article about pelean eruptions, and here’s an article about Mount Pinatubo.
Away in the constellation of Cassiopeia some 7,100 light-years from Earth, a star 40 times more massive than our Sun is blowing a giant bubble of its own material into space. Inside its magic blue sphere, the gigantic star burns at blue flame intensity – rendering a 6 light year wide envelope of hot gas around it that’s expanding outward at a speed of 4 million miles per hour. Are you ready to open wide and step inside? Then welcome to a little dimensional magic….
As always, whenever we present a dimensional visualization it is done in two fashions. The first is called “Parallel Vision” and it is much like a magic eye puzzle. When you open the full size image and your eyes are the correct distance from the screen, the images will seem to merge and create a 3D effect. However, for some folks, this doesn’t work well – so Jukka has also created the “Cross Version”, where you simply cross your eyes and the images will merge, creating a central image which appears 3D. For some folks, this won’t work either… But I hope it does for you!
NGC 7635 Cross Vision by JP Metsavainio
As the central star in NGC 7635 sheds its material, we can see it isn’t even and its appearance varies with the thickness of the surrounding gases. What appears to be cloud-like structures are very thick and illuminated by the star’s intense ultraviolet light. Believe it or not, it is here where the stellar “winds” blow the fastest and it won’t be long until these areas quickly erode. However, there is one feature that stands out more than any other – the “bubble-within-a-bubble”. What is it? It may be two distinct winds… Two distinct streamers of material colliding together.
“The bubble in NGC 7635 is the result of a fast stellar wind expanding into the interior of the larger H II region. However, the central star BD +60 2522 is appreciably offset (by about 1′) from the center of the bubble in the direction of the wall of the dense molecular cloud that defines this blister H II region.” says B.D. Moore (et al), “This offset is the result of evolution of the wind bubble into the density and pressure gradient established by the photoevaporative flow away from the cavity wall. The physical conditions around the bubble vary according to the medium into which the bubble is expanding. Away from the cavity wall the bubble is expanding into the low density interior of the H II region. Toward the wall, in the region of our images, the wind termination shock is very near the ionization front. The resulting physical structure, in which the photoevaporative flow away from the cloud wall is confined by the ram pressure of the wind.”
But, are we not seeing the proverbial forest because we’re too busy looking at the trees? “BD +60 is the ionizing star of NGC 7635, the so-called “Bubble Nebula”. NGC 7635 lies at the edge of a low-density clumpy molecular cloud and the nebula can be interpreted as a wind-blown bubble created by the interaction of the stellar wind of BD +60 with the ambient interstellar medium. While many investigations have focused on the nebula, little attention has been paid to the star itself.” says G. Rauw (et al), “Considerable progress in our understanding of the stellar winds of early-type stars has been achieved through extensive monitoring of their spectroscopic variability and the discovery that some of the cyclical variations could be related to a rotational modulation of the stellar wind. Since rotation is believed to shape the winds of Oef stars, these objects appear a priori as good candidates to search for a rotational wind modulation.”
Throughout their long term observing campaign, the group found strong profile variability on time scales of 2–3 days, variability on time scales of a few hours that might be related to non-radial pulsations, and even tentatively propose that the beating of several non-radial pulsation modes triggers transient large-scale density perturbations in a confined stellar wind that produce the 2–3 day time scale variability. “While this scenario could easily account for the lack of a single stable period (through the effect of the propagation velocity of the perturbation and the interplay of various clocks: pulsations, rotation…), it seems more difficult to explain the changing pattern of the TVS. For instance, if a density wave moves around the star, why would it not affect the absorption and the emission components in a similar manner?” says Rauw, “One possibility could be that the density perturbation affects the absorption column only as long as it remains close to the stellar surface whilst the impact on the emission lines would be larger when the perturbation has moved outwards, but this is admittedly still rather speculative.”
Just how common is it for a huge star to form a bubble around itself? “Massive stars evolve across the HR diagram, losing mass along the way and forming a variety of ring nebulae. During the main sequence stage, the fast stellar wind sweeps up the ambient interstellar medium to form an interstellar bubble. After a massive star evolves into a red giant or a luminous blue variable, it loses mass copiously to form a circumstellar nebula. As it evolves further into a WR star, the fast WR wind sweeps up the previous mass loss and forms a circumstellar bubble. Observations of ring nebulae around massive stars not only are fascinating, but also are useful in providing templates to diagnose the progenitors of supernovae from their circumstellar nebulae.” says You-Hua Chu of the University of Illinois Astronomy Department, “The fast stellar wind of a main sequence O star sweeps up the ambient interstellar medium (ISM) to form an interstellar bubble, which consists of a dense shell of interstellar material. Intuitively, we would expect around most O stars an interstellar bubble similar to the Bubble Nebula (NGC 7635) to be visible; however, hardly any O stars in HII regions have ring nebulae, suggesting that these interstellar bubbles are rare.”
Like a child chewing gum, the bubble will continue to expand. And what comes after the bubble? Why, the “bang” of course. And when it comes to a star going bang, than can only mean a supernova. “By pursuing the calculation through the various stages of massive star evolution, using a realistic mass loss history as input, we simulate the creation and evolution of a wind-blown bubble around the star up to the time of the supernova explosion.” says A. J. van Marle (et al), “The outflowing matter encounters an inner shock, where its velocity is reduced to nearly zero. The kinetic energy of the wind becomes thermal energy. This interaction creates a “hot bubble” of nearly stationary, hot gas. The thermal pressure of the hot bubble drives a shell into the surrounding interstellar medium. Here it is assumed, that the pressure driven shell will be restrained only by the ram pressure created by its own velocity and the density of the surrounding medium. This assumption is correct if we consider the surrounding medium to be cold. However, if we take photo-ionization into account the situation becomes rather more complicated. First of all, the photoionized gas will have a much higher pressure than the cold ISM. Therefore, the HII region will expand, driving a shell into the ISM. Second, the hot-bubble created by the stellar wind will now expand into a hot HII region, which means that the thermal pressure restraining the shell, will no longer be negligible compared to the ram pressure. A wind-blown bubble expanding into a compact HII region can be observed in NGC 7635.”
So how do we know when the final moments have come? “As the star ages, it becomes a red supergiant with a dense and slow wind. The number of ionizing photons drops. Therefore, the HII region disappears. Owing to the low density, recombination will take a long time, but radiative cooling will cause a decrease in thermal pressure. The hot wind-bubble, which keeps its high pressure, expands into the surrounding gas, creating a new shell. A third shell appears close to the star, as the drop in ram pressure from the RSG wind causes the wind bubble to expand inward, sweeping up the wind material.” say van Marle, “The presence of an expanding HII region changes the density structure of the nebula during the main sequence. Our main goal at this time is to simulate the circumstellar environment of stars between 25 M and 40 M at the time of the supernova explosion.”
Magic bubbles? Just stay out of the way when they pop!
Many thanks to JP Metsavainio of Northern Galactic for his magical personal image and allowing us this incredible look at distant beauty!
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At any time there are about 20 volcanoes actively erupting around the world, and about 50-70 volcanoes have erupted in the last year or so. There are a total of 550 volcanoes that have erupted in all of recorded history. Some of these active volcanos are extremely famous, often because of a tremendous loss of life. Here’s a list of some famous volcanoes:
Caribbean
Mount Pelee – A stratovolcano on the island of Martinique that killed more than 30,000 people during an eruption in 1902.
Cotopaxi – A very active volcano in Ecuador, popular with hikers.
Chimborazo – This dormant stratovolcano is the highest point in Ecuador, and actually the most distant point from the center of the Earth.
Cayambe – Another dormant stratovolcano in Ecuador. It’s the third tallest peak in the country.
Greece
Thera – The volcano that devastated the island of Santorini; one of the most powerful volcano eruptions in recorded history.
Indonesia
Krakatoa – This used to be an island in the Sunda Strait near the island of Java. It exploded in 1883 creating one of the largest eruptions in recorded history.
Mount Tambora – A stratovolcano on the island of Sumbawa in Indonesia. It exploded in 1815 producing the most powerful eruption in recorded history.
Mount Merapi – An active volcano in Indonesia, on the island of Java near the city of Yogyakarta. It’s so active that ash is almost constantly coming out the top of the volcano, and it has had several recent devastating eruptions.
Italy
Mount Etna – An active volcano on the Island of Sicily. It’s in an almost constant state of eruption, with huge ash clouds visible from the island.
Mount Vesuvius – A dangerous volcano near Italian city of Naples. It’s most famous for the devastating eruption in AD 79 that destroyed the towns of Pomeii and Herculaneum.
Mount Stromboli – An active volcano just off the coast of Sicily. It has been constantly erupting for the last 2,000 years or so.
Japan
Mount Fuji – The iconic Japanese stratovolcano – the highest point in Japan.
Mauna Loa – This active shield volcano is the second tallest volcano in the world, but it’s the biggest volcano in the world, with the most volume. It has erupted within the last century.
Hualalai – The third most active volcano in Hawaii.
Kilauea – An active volcano on the eastern side of the Island of Hawaii. It’s in an almost constant state of eruption, and one of the most active volcanoes in the world.
Kohala – The oldest of the 5 volcanoes on the Big Island of Hawaii.
Mauna Kea – The tallest volcano in the world, located on the Big Island of Hawaii.
Mount St. Helens – An active volcano in Washington State. It detonated in 1980, destroying thousands of square km of forest and killed 57 people.
Mount Mazama – This is the name for the stratovolcano that exploded more than 7000 years ago, creating what is now Crater Lake in Oregon.
Mount Rainier – An active stratovolcano that dominates the skyline over Seattle. 150,000 people live on mudflows that erupted out of the volcano 5,000 years ago.
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Mount Merapi is an active volcano in Indonesia, on the island of Java near the city of Yogyakarta. The volcano is so active that smoke can be seen coming out of the peak almost every day of the year. Mount Merapi has been erupting regularly since 1548.
Mount Merapi is located in the subduction zone, where the Indo-Australian Plate is going under the Eurasian Plate. Geologists estimate that the volcano started forming 400,000. It was largely built up by basaltic lava flows, but the lava flows have become more viscous in the last 10,000 years or so. With the thicker lava, Merapi has had more explosive eruptions and the formation of lava domes. Merapi has minor eruptions every 2 years or so, and major eruptions every few decades.
Even though it’s an extremely active volcano, thousands of people live on its flanks. Hot gas killed 43 people in 1994, and 13 villages and 1400 people were killed by pyroclastic flows during an eruption in 1930. A series of earthquakes struck Mount Merapi in April/May 2006, the most powerful one on May 27th killed 5,000 people. An eruption on June 14, 2006 spewed out a cloud of volcanic ash that covered a village several kilometers away.
We have written many articles about volcanoes for Universe Today. Here’s an article about Mount Pinatubo, and here’s an article about Mount Tambora.
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Mount Tambora is an active stratovolcano on Sumbawa island in Indonesia. It once measured 4,300 meters tall, making it one of the tallest mountains in Indonesia. It’s most famous for an enormous eruption in 1815, when the volcano detonated in the most powerful eruption in recorded history. After 150 cubic kilometers were blasted out of the volcano, and the caldera collapsed, Tambora had dropped down to 2,700 meters.
Tambora had only 3 eruptions over the previous 5,000 years, and none were very severe. But in 1812, Mount Tambora became much more active, culminating in a series of eruptions in April, 1815. On the evening of April 10th, 1815, witnesses saw three huge columns of flame rising up from the volcano. Pumice rocks rained down around the volcano, followed by clouds of ash a few hours later.
Geologists have estimated that Mount Tambora erupted with a force of 7 on the Volcanic Explosivity Index; that’s 4 times more powerful than the 1883 Krakatoa eruption. The ash cloud reached Borneo and Sulawasi islands, located 1,300 kilometers away. Historians argue how many deaths caused by the eruption itself, but estimates range from 10,000 killed by the eruption outright to almost 100,000 when you include the disease and starvation after the eruption.
The effects from the Mount Tambora eruption were felt around the world. It released so much sulphur into the atmosphere that the entire planet was cooled. The following year was known as the year without a summer. Snow fell in Quebec in the middle of summer, and persistent fog obscured much of the Northeastern US. Average annual temperatures dropped by 0.4 to 0.7 degrees C. It created the worst famine in the 19th century.
We have written many articles about volcanoes for Universe Today. Here’s an article about Mount St. Helens, and here’s another about Mount Pinatubo.
A team of astronomers at the University of Warwick think they’ve finally explained what caused the bizarre transient object SCP 06F6. By comparing the optical spectrum of SCP 06F6 to that of carbon-rich stars in our own galaxy, the team concludes the sudden outburst was not a low-energy local event but a supernova-like explosion within a cool carbon-rich atmosphere some 2 billion light years away. If they’re right, it means the collapse of carbon-rich stars may lead to supernovae unlike any yet seen.
First observed in 2006 by U.S. researchers on images from the Hubble Space Telescope, SCP 06F6 flashed suddenly then faded from view over some 120 days. The U.S. team published their findings in September 2008. But they had no idea what might cause this outburst. The event was so unusual, if fact, that astronomers had didn’t know whether SCP 06F6 was located in our own galaxy or at the other end of the universe. Talk about experimental uncertainty!
The Warwick team noticed the optical spectrum of SCP 06F6 looked a lot like light from cool stars with molecular carbon in their atmosphere. But to get a close spectral match with SCP 06F6, the team had to apply a redshift to the spectra of the carbon stars to correspond to a rapidly receding object some 2 billion light years away. The large distance and the sudden appearance of SCP 06F6 suggest the object may be related to the sudden collapse of a carbon-rich star. If so, it’s a brand new type of supernova.
But questions remain. SCP 06F6 seems to be alone in space… it has no known visible host galaxy. And the 120-day time scale of the object’s rise and fall in brightness is four times longer than most Type-II supernovae (the kind caused by the core-collapse of a massive star).
What’s more, X-ray observations by the European satellite XMM-Newton show the object blasts out up to 100 times more X-rays energy than expected from a typical Type-II supernova.
The strong X-ray emission may suggest the star was ripped apart by a black hole rather than exploding on its own. But according to Boris Gansicke, the lead researcher of Warwick team, “The lack of any obvious host galaxy for SCP 06F6 would imply either a very low black hole mass (if black holes do exist at the centres of dwarf irregular galaxies) or that the black hole has somehow been ejected from its host galaxy. While neither is impossible, this does make the case for disruption by a black hole somewhat contrived.”
The findings were published in the June 1, 2009 issue of Astrophysical Journal Letters.
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The shield volcano Mauna Kea is the tallest volcano on Earth, rising to a summit of 4,205 meters above sea level. It’s one of the 5 volcanoes that make up the Big Island of Hawaii. Mauna Kea means “white mountain” in the Hawaiian language because its summit is regularly covered in snow during the winter.
Scientists believe that Mauna Kea began erupting about 1 million years ago. It’s fed by magma from the Hawaiian hotspot; a volcanic vent that continues to pump out magma while the Pacific Plate slowly moves over top of it. This has created a chain of islands thousands of kilometers long called the Hawaiian archipelago. It’s believed that Mauna Kea transitioned from an active volcano to a post-shield stage of volcanic evolution about 200,000 to 250,000 years ago. The last eruption was thought to have occurred about 4000-5000 years ago.
Because of its high altitude, the peak of Mauna Kea is an excellent spot for astronomical observing. The summit of the volcano is above 40% of the Earth’s atmosphere, and 90% of the water vapor, allowing for extremely clear skies. Some of the largest, most powerful telescopes in the world are located atop Mauna Kea, including the Keck observatories, and the Gemini North telescope.
During the winter, Mauna Kea is coated in a thin layer of snow, and there are regions on the mountain where you can ski or snowmobile. And scientists have discovered evidence that large glaciers formed during the last period of world wide glaciation – about 11,000 years ago.
We have written many articles about volcanoes for Universe Today. Here’s an article about Mauna Loa, and here’s an article about Kilauea.
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Earth’s largest volcano is Mauna Loa, located on the Big Island of Hawaii. Although it only rises 4 km above the surface of the Pacific Ocean, that’s just the tip of the iceberg. Mauna Loa descends another 5 km down to the sea floor, which has been pushed down another 8 km by the mass of Mauna Loa. When you add that all up, the summit of Mauna Loa is 17 km above its base. It’s not the tallest volcano on Earth, though, it’s actually 37 meters shorter than Mauna Kea.
Half of the island of Hawaii is made up by Mauna Loa, and it amounts to 85 percent of all the other Hawaiian islands combined. Scientists believe that Mauna Loa has been erupting for at least 700,000 years, and may have emerged above sea level 400,000 years ago. Furthermore, Mauna Loa is one of the world’s most active volcanoes having erupted 33 times since detailed records began in 1843. Its most recent eruption was in 1984, and it’s almost certain to erupt again in the near future.
As with all of the Hawaiian volcanoes, Mauna Loa gets its magma from the Hawaiian hotspot. This is a chamber of magma that has created all the islands in the Hawaiian archipelago. The slow movement of the Pacific Plate has created a succession of volcanic islands that stretch thousands of km across the ocean. Nearby Mauna Kea is dormant, Mauna Loa is active and the smaller Kilauea is in an almost constant state of eruption.
Mauna Loa is a shield volcano. This means it has wide, gently sloping flanks. The basalt lava that erupts out of Mauna Loa and the other Hawaiian Islands has a high viscosity, and can flow for dozens of kilometers. Explosive eruptions on shield volcanoes are rare. Scientists have detected a magma chamber about 3 km below the surface of Mauna Loa, and smaller chambers beneath rift zones on the volcano’s flanks.
We have written many articles about volcanoes for Universe Today. Here’s an article about Kilauea, and here’s an article about Krakatoa.
Mount Pinatubo is an active stratovolcano on the island of Luzon in the Philippines, and the site of one of the most powerful recent eruptions. In June 1991, the volcano produced the second largest terrestrial eruption of the 20th century (after Novarupta), and the largest eruption in living memory. At least 800 people lost their lives in the eruption, but this was lower than it could have been because of an organized evacuation effort.
Pinatubo is located in the Cabusilan Mountain range, located on the west coast of the Island of Luzon. It’s a stratovolcano made up of successive layers of andesite and dacite. Its richly forested slopes were home to several thousand indigenous people. Before the eruption, it rose to an elevation of 1745 meters, but now it’s only 1485 meters tall.
Scientists had many warnings that Pinatubo was about to erupt, and this allowed such a thorough evacuation. On July 16, 1990, a magnitude 7.8 earthquake struck about 100 km north of Pinatubo. And then in March/April 1991, molten rock was detected rising to the surface from more than 32 kilometers beneath Pinatubo. This triggered more small earthquakes through April, May and early June.
On June 12, 1991, millions of cubic meters of magma reached the surface, beginning several days of eruptions. Even more magma reached the surface on June 15th, ejecting more than 5 cubic kilometers of material. An ash cloud rose 35 kilometers into the air, covering the surrounding region in meters of ash. Dangerous pyroclastic flows of hot ash, rock and water surged down the sides of the volcano, destroying everything in their path. The huge eruption gouged out a caldera 2.5 km across.
The eruption was so significant that the ash darkened the atmosphere, and caused worldwide temperatures to drop by 0.5 degrees C.
We have written many articles about volcanoes for Universe Today. Here’s an article about Mount St. Helens, and here’s an article about Krakatoa.
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The most powerful and devastating volcanic eruption in the history of the United States was the explosion of Mount St. Helens. This active stratovolcano, located in Skamania County, Washington detonated on May 18, 1980, killing 57 people, destroying hundreds of homes, and flattening hundreds of square kilometers of forest. The eruption tore off the top of the mountain, reducing its height from 2,950 meters to 2,550 meters.
Mount St. Helens is just one volcano in the Cascade Range of mountains that stretch down the west coast of North America. There are many other famous volcanoes in this region, like Mount Ranier, Mount Hood, and Mount Shasta. Helens is a large eruptive cone made up of several layers of lava rock interlaced with ash, pumice and other deposits. There are layers of basalt and andesite, and several domes of dacite lava have broken through.
Scientists believe that Mount St. Helens started forming about 40,000 years ago, and it’s considered the most active volcano in the Cascade Range. Before its eruption, St. Helens was the 5th-highest peak in Washington state; it was nicknamed the Mount Fuji of America. It measures about 10 km across the base and rose about 1,500 meters above the surrounding landscape.
And so, on May 18, 1980, Mount St. Helens erupted catastrophically, after nearly 2 months of local earthquakes and steam eruptions – scientists measured more than 10,000 minor earthquakes leading up to the eruption. But it was a magnitude 5.1 earthquake on May 18th that caused the volcano’s bulging north flank to slide away in the largest landslide in recorded history. This released a huge blast of hot gas, steam and rock debris that swept downhill from the summit. This pyroclastic flow melted snow and ice on the mountain, which added to the torrent of material streaming down the river valleys leading from the volcano. A plume of ash rose 19 kilometers into the air, covering 57,000 square kilometers of the Western United States.
Mount St. Helens is still active, and scientists have discovered dozens of extrusions of thick, pasty lava. A new dome is taking shape. It’s now about 1,100 meters in diameter and 250 meters tall.
We have written many articles about volcanoes for Universe Today. Here’s an article about Kilauea in Hawaii, and here’s an article about Krakatoa.
