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Kilauea is not the "blow your top" kine of volcano. As a geologist friend of mine stated, it "isn't the kind that blows up, it just oozes, sometimes for centuries".
hi leilaniguide,
if you read the article I linked, itÔs not saying "blow your top" as in blow the top away like Mt. St. Helens.
ItÔs saying explosive eruptions from out of the caldera, which is not the same thing, that goes on INSTEAD of the oozing in alternate cycles for hundreds of years at a time.
They have used carbon dating to establish this new view of Kilauea that was published in 2011, a new view that basically said scientists were wrong about Kilauea if they thought it just oozes.
Here is a more straight from the geologistÔs mouth explanation:
KilaueaÔs Explosive Past and Future from Earth Magazine
http://www.earthmagazine.org/article/kil...and-future
Similar to what Carol was saying, explosive cycles seem to happen when groundwater comes into contact with magma. However, the theory is that LESS magma building up leads to explosive cycles, not more magma pressure. It is the magma pressure remaining high that maintains the caldera floor safely above the groundwater level, as I understand it. The article explains it really well, and I am a non-geologist, so I wonÔt try to paraphrase it any more than that.
Excerpt (long for the benefit of Punawebbers with slow connections who dislike following links.
quote:
Kilauea is capable of explosive eruptions and has already killed far more people than any other volcano in what is now the United States. Scientists know there are numerous lava fountains and spattering eruptions at Kilauea, such as on Jan. 18, 2011, from KilaueaÕs lava lake at Halemaumau, but these eruptions are mild compared with the violent eruptions now under study.
Now, researchers have learned that violent eruptions at Kilauea are not always isolated events. Over the past 2,500 years, violent eruptive periods lasting centuries have alternated with periods of quiet flows, such as we have seen for the past 29 years. Once an explosive period has begun, conditions on the Big Island will be very different from those on which the past hazard assessment was based. Volcanologists are currently at work on revising the hazard assessment before the next explosive period begins.
A History of Violence
Scientists at the U.S. Geological SurveyÕs (USGS) Hawaiian Volcano Observatory (HVO), perched on the rim of KilaueaÕs caldera, recently assembled a rough chronology of KilaueaÕs explosive and quiet periods using carbon-14 dating techniques. Their investigation, aided by colleagues at the Smithsonian Institution and the University of Hawaii, accords with oral accounts handed down by native Hawaiians and published by Christian missionaries.
The danger that Kilauea poses is significant, said Don Swanson of HVO at the annual meeting of the American Geophysical Union in San Francisco, Calif., last December, where he reported on research he led. SwansonÕs investigation revealed that KilaueaÕs most explosive eruptions are not isolated incidents, but part of long-term trends, he reported.
The new research involved radiocarbon dating of charcoal formed over the past 2,500 years. Some of the charcoal formed when lava flowed through vegetation and burned it; more formed when ash fell on vegetation and burned it. To obtain their samples for testing, Swanson and his colleagues scraped and dug at the base of lava flows, where charcoal is best preserved. They also found charcoal embedded in ash deposits that they encountered in excavations. All told, the team obtained 200 specific ages, half from lava samples and half from ash from several tens of eruptions.
The carbon dating, carried out at Lawrence Livermore National Laboratory in California and at the University of Arizona, revealed that Kilauea alternates between periods of quiet lava flows and explosive eruptions that last centuries. The most recent explosive period lasted from about A.D. 1500 to 1800, during which Kilauea violently erupted at least 20 times Ñ with the most deadly being the 1790 eruption.
Evidence suggests that most of the fatalities in the 1790 eruption were caused by a pyroclastic density current, or PDC, a mixture of hot gas and volcanic ash moving at hurricane speed that engulfed and killed the warriors and their accompanying families by heat and asphyxiation. (PDC is a general term that encompasses several types of events. HVO scientists characterize those that have occurred at Kilauea as surges. Another, perhaps better-known term, pyroclastic flow, describes a different type of PDC.) Scientists at HVO have located, near the observatory, traces of PDC deposits from the 1790 eruption, as well as footprints made in muddy volcanic ash just prior to the arrival of the PDC that may record the last steps of some of Ke#333;uaÕs warriors.
The 1790 eruption was not, however, KilaueaÕs most powerful. Almost 1,000 years earlier, in about A.D. 800, an explosive eruption sent small stones up to 18 kilometers away, and deposited a 4.4-kilogram rock five kilometers from the vent. That eruption was part of an explosive period lasting from about 200 B.C. to A.D. 1000. The signs that had previously been attributed to one eruption in 200 B.C. are now known to have resulted from many explosive eruptions throughout that 1,200-year period. Before 200 B.C. and in between the explosive periods of 200 B.C. to A.D. 1000 and 1500 to 1800, Kilauea was in a ÒquieterÓ lava flow period, as it is today. That is not to say that quieter periods cannot also be destructive: Since 1983, when the current, almost nonstop, lava flows began, 213 structures have been destroyed and 13.5 kilometers of highway covered and rendered impassable. All told, over the 2,500-year period covered by the new research, Kilauea was in an explosive state 60 percent of the time.
What Causes One Type of Eruption Versus Another?
During the explosive periods, Swanson says, each individual explosive eruption may have lasted hours to weeks, with quiet periods between lasting weeks to a few decades. Likewise, during periods of effusive flow, short-lived fountaining eruptions like the one in March 2011 can occur.
But what causes KilaueaÕs transition from one state to the other? The answer is related to the condition of the volcanoÕs caldera, the crater at its summit, Swanson says. The depth of the caldera and its relationship to the depth of the water table is key to understanding KilaueaÕs eruption cycles.
The water table today is about 615 meters below the rim of the caldera, whereas the floor of the caldera is at a depth of about 120 meters. ÒWe think this is a good measure of the minimum depth that the caldera floor must have reached to initiate explosive activity,Ó Swanson says. ÒWhen the caldera is deep enough to intersect the water table, groundwater can become involved in the eruptions, which are predominantly explosive owing to the steam produced by heating of the water.Ó
Over time, Swanson says, Òthe long periods of explosive activity imply that the caldera remains that deep for equally long periods, or that it begins to fill and then recollapses down to a depth of 600 meters or greater below the calderaÕs rim. Once the caldera is able to fill with lava to a shallower depth and doesnÕt collapse, the explosive period ends and the cycle of lava flows begins.Ó
In addition, HVO geologists conclude that when the supply of magma below the floor of the caldera is high, as it currently is, eruptions occur as lava flows. ÒIf, however, the magma reservoir drops significantly and therefore no longer supports the summit, the caldera walls can collapse,Ó Swanson says. ÒExplosive eruptions can then occur, spewing rock from the collapsed walls high into the air, along with ash and lava. This happens occasionally during periods of lava flows, but for Kilauea to transition into a continuing explosive period, the magma supply to the shallow reservoir must remain low.Ó
The reason why the magma supply to the reservoir might decrease is not known, Swanson says, but there are several possible explanations. Basically, either less magma is rising from the hot spot below the ocean floor, or it is being diverted prior to reaching the reservoir. In the latter case, the magma might flow directly to the ocean floor or, less likely, he says, it may enter the neighboring Mauna Loa system. ÒIt is probably the variation of magma supply to Kilauea that is the most fundamental aspect of the cycles,Ó he says. In short, Òlow supply leads to long periods dominated by explosive activity, and high supply to long periods of lava flows.Ó
The Role of Mauna Loa
Geologist Frank Trusdell, who specializes in Mauna Loa at HVO, has found an inverse relationship between Kilauea and its 4,170-meter-high neighbor: During some periods in the past, such as between 1823 and the early 1900s, when Kilauea was quiet, Mauna Loa was erupting copious lava flows, and at other times, when Kilauea poured out large amounts of lava, Mauna Loa slowed to a trickle. This suggests a physical connection between the two magma systems deep underground, which both Trusdell and Swanson say is still speculative at this point. For one, Swanson says, the magmas of the two volcanoes are isotopically different and can therefore be distinguished.
Trusdell has developed a hypothesis concerning the Mauna Loa-Kilauea relationship based on historical accounts and his recent research into prehistoric eruptions. He notes, for example, that in the period between 1823 and the early 1900s, KilaueaÕs crater contained a lava lake: ÒYou walk up to the edge of this crater, and thereÕs a boiling cauldron of lava in front of you,Ó he says. At the same time, Mauna Loa was erupting copious amounts of lava.
ÒMy new hypothesis,Ó Trusdell says, Òis that if you have a standing lava lake only in the summit of [Kilauea], and the lava is not spilling over and blanketing the near-surface flanks, you actually still have modest levels of magma supply into the volcano. And in turn, what that means is that KilaueaÕs south flank is actually quite stable.Ó The south flank is KilaueaÕs downhill side, away from Mauna Loa.
When Kilauea erupts explosively, however, its south flank moves, which can now be determined with GPS measurements. When the south flank is not buttressing KilaueaÕs summit, Mauna Loa pushes against it. ÒYou end up creating more space in Mauna Loa,Ó Trusdell says, Òwhich reduces the pressure of the magma withinÓ and therefore the propensity to erupt.
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Aloha everybody!,
And thank you for the info.The info was not for me it was for co workers where i work in Miami Florida.Most people here thing if you where born and raised in Hawaii you no everything about volcano's and lava! And believe me i no nothing about those subject's. The islands that i was born and raised the volcano's are not active at this time was never active in my 45yrs that i was on those islands. So thank you for helping me explain to my co workers something that i don't really no nothing about..
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Kathy, thanks for posting this. It is important info to get out. It sounds safe for now, but that could change!
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quote:
Originally posted by KathyH
Before 200 B.C. and in between the explosive periods of 200 B.C. to A.D. 1000 and 1500 to 1800, Kilauea was in a ÒquieterÓ lava flow period, as it is today. That is not to say that quieter periods cannot also be destructive
That period from 1000-1500 was when the flows were produced that covered the major Puna subdivisions (Royal Hawaiian through Fern Forest, Hawaiian Acres, Orchidland, and HPP). A huge area, and no doubt extremely destructive to the communities that existed there at the time.
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That same time period is when the Mauna Loa Panaewa flow occurred...covering most of the east side of Hilo all of the way to Kaloli Pt (creating Blondes Reef that the Hilo breakwater sits on, Moku Ole (Coconut Island), covering the lands of Hilo Industrial & shopping center areas, extending along mush of the Shipman lands and creating Kaloli pt.
The Panaewa flow has some really cool characteristics, in that you can easy find crystals of horneblend (older magma) and olivine (new magma)& gives many of Hilos beaches the salt & pepper & green blend of sands).
This is a very similar basalt to the flows on the moon (and having those characteristics is very rare on earth based magma flows).
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"That period from 1000-1500 was when the flows were produced that covered the major Puna subdivisions (Royal Hawaiian through Fern Forest, Hawaiian Acres, Orchidland, and HPP). A huge area, and no doubt extremely destructive to the communities that existed there at the time".
didnt the first inhabitants arrive about 1000 years ago? the eruption would have been one heck of a beacon.
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Kathy what is up with your keyboard and the 0 it's kind of driving me crazy!
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as far as being "safe" I took a que from my dog - best place eyes closed is head under the blankie - grin
there are no guarantees in life except for death
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