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NileQueen
Joined: 21 Jul 2007
Posts: 77
Location: southern Indiana/Cincinnati Ohio
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 Posted: Tue Aug 14, 2007 3:19 pm Post subject: |
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Do you recall which show? Was it NOVA or discovery channel?
The flood basalts seem to coincide with major geological events (extinction boundaries) and may indeed be linked to impacts.
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billiards
Site Admin
Joined: 21 Jul 2007
Posts: 81
Location: London, UK
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| Posted: Tue Aug 14, 2007 6:04 pm Post subject: |
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| NileQueen wrote: | | Quote: |
Public release date: 13-Aug-2007
Contact: Sofia Valleley
svalleley@esf.org
33-388-762-149
European Science Foundation
Keeping the Earth's plates oiled
Earth’s surface is a very active place; its plates are forever jiggling around, rearranging themselves into new configurations. Continents collide and mountains arise, oceans slide beneath continents and volcanoes spew. As far as we know Earth’s restless surface is unique to the planets in our solar system. So what is it that keeps Earth’s plates oiled and on the move?
Scientists think that the secret lies beneath the crust, in the slippery asthenosphere. In order for the mantle to convect and the plates to slide they require a lubricated layer. On Mars this lubrication has long since dried up, but on Earth the plates can still glide around with ease.
Beneath continents the asthenosphere appears at around 150km depth, while under oceans it can be as shallow as 60km. Above the asthenosphere lies the lithosphere: a more rigid layer that includes the crust. By 220km depth the asthenosphere comes to an end and the mantle goes back to a less flexible state. |
Hmm. Can we be sure about this?
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I don't see anything wrong with this except for the use of the word "slippy". I don't believe the asthenosphere is slippy, the lithosphere doesn't just glide over it like a puck on an ice rink, in fact it is very hard to resolve the asthenosphere to see deformation structures because it does not reflect waves back up at us. It is a low velocity zone (LVZ), which is a seismological term meaning that the zone's wavespeed is heterogeneously lower than its surroundings. LVZs tend to refract seismic energy away from the surface, therefore seismic reflection is out of the window, seismologists have to use tomographic techniques to learn about the asthenosphere which have only a limited resolution. |
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scpg02
Joined: 22 Jul 2007
Posts: 221
Location: Sacramento
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| Posted: Tue Aug 14, 2007 7:33 pm Post subject: |
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| NileQueen wrote: | Do you recall which show? Was it NOVA or discovery channel?
The flood basalts seem to coincide with major geological events (extinction boundaries) and may indeed be linked to impacts. |
It wasn't NOVA, a good show but I rarely watch it. Probably one of the cable science channels. Might be able to dig something up with a web search. And yes extinction played a big part, may have actually been the main thrust of the original investigation. |
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scpg02
Joined: 22 Jul 2007
Posts: 221
Location: Sacramento
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| Posted: Tue Aug 14, 2007 7:54 pm Post subject: |
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As I recall the show said the impact was so large the Earth rang like a bell. The shockwave went around the globe and met where the Siberian traps are, causing the eruption and subsequent extinction. One of these links has a graph but I haven't really looked at it.
http://news.bbc.co.uk/1/hi/sci/tech/2030075.stm
Volcanic 'flood' linked to extinction
| Quote: | A huge outpouring of molten rock 250 million years ago may have been the decisive factor in the deaths of nearly all lifeforms on the Earth at that time.
The lava that gushed out of the ground was at least twice as extensive as previously thought, a team of international researchers now reports.
Its work suggests the "volcanic flood" was a kilometre and a half deep and covered an area half the size of Australia.
Its timing coincides with the disappearance from the fossil record of up to 90% of all marine species and 70% of land vertebrates.
Researchers suspect the upwelling released vast quantities of gas into the atmosphere, rapidly changing environmental conditions and making it impossible for most lifeforms to continue.
~snip~
Some scientists strongly suspect the impact of an asteroid or comet may also have played a significant role.
American researchers have found chemical traces in rocks from the time which they believe point to an extraterrestrial collision. |
http://users.tpg.com.au/users/tps-seti/crater.html
Asteroid/Comet Impact Craters and Mass Extinctions
by Michael Paine
| Quote: | The following graph shows impact craters on Earth by age and diameter. Also shown are the main geologic boundaries involving mass extinctions (tall, bold lines), minor boundaries (thin, short lines - fewer extinctions) and the approximate timing of "flood basalt eruptions". Originally the graph only showed craters which aligned with major extinction events but it was considered better to show all craters 20km diameter or more to avoid "counting the hits and ignoring the misses". Those which appear to align with a geologic boundary are shown as dark blue diamonds. The most notable is Chicxulub at the Cretaceous/Tertiary boundary - the event that saw the extinction of the dinosaurs.
Since multiple impacts appear to be very common throughout the solar system it is expected that some of the smaller craters are associated with other major impacts, evidence of which has not been discovered or has vanished over time. For example, the Triassic/Jurassic and Jurassic/Cretaceous boundaries appear to involve multiple impacts. Craters 40km diameter or more are likely to be caused by 2km diameter asteorids or comets. Such impacts would probably result in severe global climate disruption but it takes an asteroid/comet 10km or larger to cause mass extinctions. It is estimated that such impacts occur, on average, once every 50 to 100 million years. |
And just for balance:
Link
Contemporaneous mass extinctions, continental flood basalts, and ‘impact signals’: are mantle plume-induced lithospheric gas explosions the causal link?
J. Phipps Morgan, , T. J. Reston and C. R. Ranero
Abstract
| Quote: | Contemporaneous occurrences of the geologic signals of ‘large impacts’, craton-associated continental flood basalts, and mass extinctions have occurred far too often during the past 400 Myr to be plausibly attributed to random coincidence. While there is only a 1 in 8 chance that even one synchronous large impact within the interval of a continental flood basalt and mass extinction event should have happened during this period, there is now geologic evidence of four such ‘coincidences’, implying causal links between them. The 66 Ma (K–T) evidence suggests that impacts do not trigger flood basalts, since the Deccan flood basalt had started erupting well before the Chicxulub impact event. If extraterrestrial impacts do not trigger continental flood basalt volcanism, then we are really only left with two possible resolutions to the dilemma posed by these mega-coincidences: either the reported ‘impact signals’ at the times of great mass extinctions are spurious or misleading, or – somehow – a terrestrial process linked to continental rifting and the eruption of cratonic flood basalts is sometimes able to generate the shocked quartz, microspherules, and other geologic traces commonly attributed to large extraterrestrial impacts, while also triggering a mass extinction event. Here we explore a promising mechanistic link: a large explosive carbon-rich gas release event from cratonic lithosphere, triggered by mantle plume incubation beneath cratonic lithosphere, and typically associated with the onset phase of continental rifting. Sudden CO2/CO and SO2 release into the atmosphere would provide the primary killing mechanism of the induced extinction event. Such explosive deep-lithospheric blasts could create shock waves, cavitation, and mass jet formation within the venting region that could both create and transport a sufficiently large mass of shocked crust and mantle into globally dispersive super-stratospheric trajectories. We suggest these be called ‘Verneshot’ events.
Author Keywords: mass extinctions; flood basalts; large impacts; cryptoexplosions |
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Baywax
Joined: 23 Jul 2007
Posts: 113
Location: Pacific West Coast
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| Posted: Tue Aug 21, 2007 5:48 pm Post subject: |
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I found this while searching for the full explaination of the "Lava Lamp Effect".
Movement
| Quote: | | Due to the temperature difference between the Earth's surface and outer core, and the ability of the crystalline rocks at high pressure and temperature to undergo slow, creeping, viscous-like deformation over millions of years, there is a convective material circulation in the mantle. Hot material ascends as a plutonic diapir (somewhat akin to a lava lamp), perhaps from the border with the outer core (see mantle plume), while cooler (and heavier) material sinks downward. This is often in the form of large-scale lithospheric downwellings at plate boundaries called subduction zones. During the ascent the material of the mantle cools down both adiabatically and by conduction into surrounding cooler mantle. The temperature of the material falls with the pressure relief connected with the ascent, and its heat distributes itself over a larger volume. Because the temperature at which melting initiates decreases more rapidly with height than does a rising hot plume, partial melting may occur just beneath the lithosphere and causing volcanism and plutonism. |
[url]http://en.wikipedia.org/wiki/Mantle_(geology)[/url]
Mantle Plumes
Here's a good article on Mantle Plumes and it does actually mention the lava lamp effect.
| Quote: | | In this lecture we discuss hotspots and mantle plumes, the phenomena that explain why volcanoes can occur away from plate boundaries. Among the topics that will be discussed are the characteristics of hotspots and mantle plumes, the evolution of mantle plumes, and the interesting links that might be made between continental rifting, climate change, extinctions, magnetic reversals and mantle plumes. |
http://www.nipissingu.ca/faculty/ingridb/geology/hotspots.htm
Lava Lamp Plumes...
| Quote: | | Some authors (e.g., Cox & Van Arsdale, 2002) have held on to the Morgan-Crough Bermuda plume model, which would require a a pulsating (“lava lamp”) plume and/or severe control by lithospheric structure on melts rising into or erupting onto the crust. In support, Cox & Van Arsdale (2002) note that predicted Bermuda hotstpot tracks cross the ca. 65 Ma igneous activity in Mississippi, and also the ca 115 Ma activity in Kansas (Figure 2). However, there is no “LIP” (large igneous plateau) in Kansas or elsewhere that might represent the effects of a “plume head” at the beginning of the putative Bermuda plume track. Moreover, Cretaceous and Cenozoic igneous rocks elsewhere in North America (some are noted in simplified form in Figure 2) would necessarily require other plumes (McHone, 1996) [Ed: See also CAMP page]. |
http://www.mantleplumes.org/Bermuda.html
and lastly but not leastly... 
| Quote: | | What’s a lava lamp got to do with Northwest earthquakes? Visitors to the exhibit will learn that, too. |
http://www.washington.edu/burkemuseum/earthquakes/press/bigone.html
_________________
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory. Leonardo Da Vinci
Time flies like an arrow, fruit flies like a banana.
W.C. Fields |
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scpg02
Joined: 22 Jul 2007
Posts: 221
Location: Sacramento
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| Posted: Tue Aug 21, 2007 6:07 pm Post subject: |
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| Quote: | | Lava Lamp Plumes... |
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Baywax
Joined: 23 Jul 2007
Posts: 113
Location: Pacific West Coast
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| Posted: Tue Aug 21, 2007 10:04 pm Post subject: |
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That's the action!
The action of the lava lamp-like effect with denser material rising and falling inside of what her NileQueenishness has determined to be a "oblate spheroid" (earth) was considered to perhaps be the cause of the sea level rising to heights that exceed those caused by hydro and glacio-isostatic lift during the last "ice age".
Here's a time-lapse film of a lava lamp for your entertainment
http://www.youtube.com/watch?v=-Z0ne-xHlaM
The thread that thought about the geo-lava-lamp came up in is here:
http://www.physicsforums.com/archive/index.php/t-165114.html
Run away Lava...lamp...
http://www.austin-animation.flixprod.com/lava_lamp.mpg
_________________
Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory. Leonardo Da Vinci
Time flies like an arrow, fruit flies like a banana.
W.C. Fields |
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