I happen to live directly over a magma plume that is currently erupting to the surface for the past 20 years. The lava flows, when hardened, look exactly like the Crater of the Moons (which I last visited in 1982) lava flows, and it's hard to tell which place you're at just by looking at the hardened lava. The volcano cap over our magma plume is now about 30,000 feet thick, half of which is submerged under the Pacific Ocean, and the other half jutting upwards to circa 15,000 feet elevation. Of course, the entire island chain was formed by drifting of the continental plate over our plume, carrying away one island after another in a northwesterly direction as they were formed, and the only active volcanoes are those on the Island of Hawaii (Mauna Loa, which erupts every 10 years or so, Kilauea, which has been in continuus eruption for the last 20 years, and which is known to have experienced 100-year eruptive events, and Hualalai, which erupts every century or so), which is directly over the plume. Of course, we have another active volcano currently erupting just to the south of us, about 10,000 feet from the surface (Loihi), which will reach the surface and make the Big Island even bigger in roughly another million years. Technically, Haleakala on Maui is still 'active', because it had a minor side-flank cinder cone eruption circa 1805 that lasted a day or two. We've placed our best telescopes on the 'extinct' volcano Mauna Kea, since it last erupted circa 20,000 years ago, during the ice ages, leaving surface basalt that hardened under glaciers, making for excellent stone material prized by the original inhabitants as the best in the islands for adzes, etc. The last phases of this type of volcanic activity results in 'cinder cones' which dot the volcanoes by the hundreds. Flank eruptions produce copious amounts of cinder (rock with lots of gas-pockets) that is spit out in the form of a cone, with the much lighter 'ash' being wind-driven onto the slopes of the volcano proper, forming a thick layer (20 to 50 feet in some areas) that makes excellent farmland, formerly used for sugarcane and now used for a wide variety of other crops. About 20% of the island's electricity comes from two geo-thermal wells drilled by Puna Geothermal Ventures (PGV). The PGV wells sometimes have had sulfur dioxide releases which have caused them problems, otherwise all of the electricity would likely now be from geothermal. So, what is the prospect for geothermal drilling in the Yellowstone Caldera region?
I've heard that they have considered drilling and using explosives to relieve the pressure but I bet that's just a bunch of hype by radical extremists. What happened to all the previous threads on Sciforum from last year? I guess Tristan deletes them after so long but we discussed all this before. What a pity we can't just look up what was posted back then. Hawaii is a bit of a geomagnetic anomaly in plate tectonics and still not fully explained. The Pacific Plate moves northwest but the hot-spot is unusual because it is caused by an upwelling in the mantle between two convection cells in the asthenosphere. Differences in magnetic orientation in the Hawaii-Emperor Chain indicate that at some point in history the hot-spot itself did move south and was not always stationary. Geez, we posted this all once before so I hate to delve into researching it again, but you can see the differences in direction of the islands and the differences in the rates of formation in the following diagram: Please Register or Log in to view the hidden image! Source: http://publish.yorku.ca/~rossb/Grades/seamounts.htm
Well that image just doesn't want to post. Anyways, the other theory is that the sharp bend in the chain 2,200 miles northwest of the big island of Hawaii is due to a change in the direction of the Pacific Plate that took place some 40 mya. The hot-spot is supposed to be about 200 miles across with a few seperate narrow passageways leading to individual volcanoes.
There are indeed 3 overlapping calderas, the first erupting around 2.1 m.y., the second, much smaller erupted 1.3 m.y. and the Yellowstone Caldera which erupted 640,000 years ago. Of course, there are numerous old calderas stretching all the way across the Snake River Plain and eastern Oregon to McDermitt Caldera in northern Nevada. These calderas are age progressive from McDermitt (17 my) to the present Yellowstone caldera. I don't have time to address the rest of your post here, but will return to the subject next week.
Thanks for clearing that up. It depends on how a caldera is defined. Technically a caldera is the depression at the top of the volcano crater that folds in on itself, and there's scores of remnant cinder cones dotted throughout the Columbia Basin and the Snake River Plain, especially within the Craters of the Moon Nat'l Monument. The Wikipidea article seems to imply that the calderas and the Yellowstone volcanic activity are one and the same with only a brief reference to the underlying "hot-spot" at the end of the article. I think the article should be edited to clarify the geological stratifications and the source of the volcanic activities. The hot-spot magma chamber lies under the Yellowstone caldera.
Incorrect, or badly phrased. A caldera is a collapse structure. Following the eruption of large volumes of volcanic rock a depleted magma chamber may lack sufficient strength to support the overlying volcano. A large portion of the volcano may then collapse into the partially empty magma chamber along ring fractures, that may subsequently serve as conduits for magma.
This is what I mean when I say the Wikipedia article is misleading. Wikipedia states that "The calderas' apparent motion to the east-northeast forms the Snake River Plain. However, what is actually happening is the result of the North American plate moving west-southwest over the stationary hotspot deep underneath." In the same breath this sentence equates the caldera as being the same thing as the hotspot and as being underneath it. It should be rewritten. In the map they state that "Yellowstone sits on top of three overlapping calderas," yet the map does not show three overlapping calderas and all throughout the article, and any other place you read about this, they talk about the "Yellowstone Caldera" in the sense that there is only one. And there is only one. Have you ever read an article that refers to the "Yellowstone calderas" (plural). Do we have stratification dating of three? If so, it's not mentioned in the article, and I've never read about it as a specific distinction of three layers within the park. Also, as I said, there are scores of cinder cones dotting the Columbia Basin and the Snake River Plain that are collapsed. So it depends on how you define a caldera. Basically there are two different definitions of a caldera: one, a circular depression resulting from the collapse of a volcanoe; or two, the collapse of the entire strata of rock holding the volcano up, i.e., the loss of the structural support, and then this definition still includes any resulting vent craters. Definitions of Caldera: The American Geological Institute: "A large depression formed at the top of a volcano when the vent collapses." University of Utah Seismograph Station: "A large, roughly circular volcanic depression whose diameter is many times greater than that of its vent or vents." UC Museum of Paleontology: "A large circular volcanic depression, often originating due to collapse." United States Geological Survey: "Large, generally circular, fault-bounded depression caused by the withdrawal of magma from below a volcano or volcanoes" or "A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir." Please Register or Log in to view the hidden image!Aniakchak Caldera Source: "http://volcanoes.usgs.gov/Products/Pglossary/caldera.html "Yellowstone Park sits directly over a hot spot. The volcano is quiet today, only the geysers and hot springs remind us that there is a huge volcano under the beautiful scenery. Only 600,000 years ago a huge eruption filled the area with lava flows. After the huge eruption there was a void under the top of the volcano. The weight of the volcano caused the top to come crashing down forming the large caldera in the park." From: "Yellowstone Caldera" http://www.members.tripod.com/tdebuff/webquest.htm
this map clearly shows the three calderas. The one labeled "older caldera" was the largest eruption, producing the Huckleberry Ridge welded tuff around 2.1 m.y. This caldera is partially buried by the younger Yellowstone caldera. The Island Park Caldera produced the Mesa Falls welded tuff around 1.3 m.y. The Yellowstone Caldera exploded and collapsed around 640,000 years ago. image is from http://volcano.und.nodak.edu Please Register or Log in to view the hidden image! There is no "Snake River Caldera". As the Yellowstone hot-spot migrated to the northeast below southern Idaho (actually N America migrated to the SW), it created the Snake River Plain (a.k.a. the Snake River graben). After passage of the hot-spot, the crust cools, shrinks and allows melts from the upper mantle to erupt as basalt. The current hot-spot is melting continental (silicic) material in the Yellowtone Park area- creating the much more explosive caldera-type eruptions. Millions of years from now, Yellowstone Park will be covered over with basalts, much like the present day Snake River Plain- and Yellowstone type calderas will be erupting further to the northeast. You still need a heat source to generate hydrothermal fluids. That heat source is the partially molten rock (magma) that sits atop the Yellowstone hot-spot. The relatively rapid onset of uplift and then subsidence suggests hydrothermal fluids were probably responsible for the inflation and deflation of the surface near Norris (silicic magma is too slow due to its high viscosity). The authors also suggest migration of basaltic melts as a possibility, since they are relatively mobile.
Thanks. This map is much more accurate than the one posted on Wikepedia under "Yellowstone Caldera." I think you should repost this map on their website as it clearly shows the three calderas. Wikepidia outlines the underlieing Snake River Hot Spot and the other caldera near the Craters of the Moon but does not show three calderas at Yellowstone. Great posting!
What it comes down to.. 1.) It eventually WILL erupt 2.) It will cause worldwide effects 3.) Lots of people will die, from worldwide effects.
5) CNN and the Dems will blame Bush (or maybe Cheney since his home is nearby) 6) FEMA, once again, will be woefully inadequate
I just came back from Yellowstone. I've read in many scientific journals that state there is absolutely no threat for at least 10,000 to 100,000 years and the folks at Yellowstone confirm this. I did not get a straight answer from anyone regarding the periodicity of Old Faithful. Theories range.
Great. If you wait long enough, in another 10,000 years or so, right after the next eruption, property around Yellowstone should be a little cheaper I guess. Might have to wait a few hundred years until the Yellowstone caldera fills up again to make it worth your while. Please Register or Log in to view the hidden image!
There is nothing so unpredictable as Mother Nature. She has her own agenda which does not include the likes of humanity. Your dates may be correct, but they told the late seismologist who died on Mount St Helens that "your predictions are groundless and without substance". Mother Nature knows all and tells little.
In 1993 nine volcanologists went to study a Colombian volcano. While they were peering inside from the rim of the cone, it erupted: they all died. The volcano laughed: "Gotcha!"
Nothing is absolute. I would agree that we probably have thousands of years before the next catastophic caldera eruption at Yellowstone- but we don't have enough information to be certain. Problem is, there is no human recorded history of "supervolcano" eruptions- so we really don't know the precursors or the timing for these massive eruptions. Should they follow the pattern for smaller silicic eruptions (Mt St. Helens)? Probably. But maybe there are not many signals- and once you release just a bit a pressure, the whole system goes within a very short time period? Hope you had a interesting trip- by chance did you visit Mud Volcano?
