video for embedding at http://scitech.quickfound.net/geology_news_and_links.html
"Narrated by Roger Mudd, this video is full of detailed, informative graphics and live action that chronicles the volcanic history of the Hawaiian Islands (e.g. Kilauea and Mauna Loa).
part 2: http://www.youtube.com/watch?v=z_vvvPUl8qo
Also see: Hawaii's Spectacular Volcanic Eruptions
http://www.youtube.com/watch?v=b_rLpseMA9U
"Kïlauea—an Explosive Volcano in Hawai'i"
http://pubs.usgs.gov/fs/2011/3064/fs2011-3064.pdf
Kïlauea Volcano on the Island of Hawai'i, though best known for its frequent quiet eruptions of lava flows, has erupted explosively many times in its history—most recently in 2011. At least six such eruptions in the past 1,500 years sent ash into the jet stream, at the cruising altitudes for today's aircraft. The eruption of 1790 remains the most lethal eruption known from a U.S. volcano. However, the tendency of Kïlauea's 2 million annual visitors is to forget this dangerous potential. Cooperative research by scientists of the U.S. Geological Survey, Smithsonian Institution, and University of Hawai'i is improving our understanding of Kïlauea's explosive past and its potential for future violent eruptions...
Long considered a "milquetoast" of a volcano, erupting only photogenic lava fountains and flows, Kïlauea has the capability of quickly turning violent. Its eruption of 1790 killed a large number of people (estimates, all made decades afterwards, range from about 80 to more than 5,000) within a few hundred meters of where the Jaggar Museum and the adjacent Hawaiian Volcano Observatory stand today. And, in 1924, a too-adventurous accountant was killed while photographing the largest in a 17-day series of explosive eruptions at the volcano's summit.
Although they are not its usual style, Kïlauea produces explosive eruptions about as often as does Mount St. Helens in Washington State—several periods of multiple explosive events every millennium. Those at Kïlauea are generally smaller in volume and in area affected, but their risks are substantial. More than 5,000 people a day visit Kïlauea's summit, where most of the explosive eruptions take place, and hundreds live nearby. A busy highway now passes through the area where so many died in 1790—a tragedy that, by itself, makes Kïlauea historically the most lethal of all volcanoes in the United States...
Much more powerful eruptions occurred in the more distant past. One lar ge explosive eruption at Kïlauea's summit 1,000-1,200 years ago sent golf-ball-size dense w all rocks to the south coast of the island, 18 km (11 miles) away. One block 24 cm (9.5 inches) across and weighing 4.43 kg (9.7 lbs) fell 5 km (3 miles) from the v ent. Several other large explosive eruptions, including the deadly one in 1790, produced volcanic ash that blew southeast, east, and northeast of the summit, as recognized from the distribution of the ash deposits...
Groundwater or surface water probably has played a major role in most of Kïlauea's explosive eruptions. If water is heated under pressure and the pressure then relieved, it can flash into steam, rapidly expanding and providing the propellant for explosive eruptions. Scientists theorize that, when the caldera is deep enough to be at or below the water table (the level below which rocks are saturated with water), water can seep into the vent and explosive eruptions can take place. The water table is currently about 500 m (1,640 ft) below the floor of the caldera. If the caldera collapsed to about that level—as it did around 1500 C.E., probably remaining there until 1790—explosive eruptions could likely occur. In 1924, geologists noted that lava drained from Halema'ma'u Crater to a depth apparently below the water table; rock falls from the collapsing walls of the crater dammed rising steam, pressure built up, and explosive eruptions occurred.
Not all of Kïlauea's explosive eruptions may be related to groundwater, however. The summit explosive eruptions of 2008, and likely also those at Pu'u'Ö'ö, were apparently propelled by gas carried by, and released from, magma independent of groundwater. The very powerful eruption around 800-1000 C.E. carried up fragments of almost solidified magma that was apparently crystallizing at a depth of 5-6 km (3-3.5 miles) when the eruption began. At such depths, carbon dioxide (CO2) is bubbling from the magma, and perhaps a buildup in CO2 pressure triggered that explosive eruption.
volcano, geology, lava, eruption, Kilauea, Mauna Loa, USGS, Smithsonian, Roger Mudd, Hawaii, Hawaiian Islands,
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Inside Hawaiian Volcanoes pt2-2 1989 Smithsonian Roger Mudd 14minby webdev17402 views
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