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Andre
Joined: 21 Jul 2007
Posts: 298
Location: Germany - The Nederlands
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 Posted: Sat Jul 21, 2007 8:19 pm Post subject: Earth solid? |
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Earth is not really solid as in the third rock from the sun. that's a mistake that many people make, an easy assumption for geologists and planetary physisists. But this is how it appears to work:
plenty of fluids in there, it's more like a raw egg.
But the Earth is also this:
and all that is doing this:
Now for many specialities you will find that they can cope with two of the elements out of the three. But we're trying to find out what if we can think of everything.
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billiards
Site Admin
Joined: 21 Jul 2007
Posts: 81
Location: London, UK
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| Posted: Sat Jul 21, 2007 11:31 pm Post subject: |
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Hi Andre,
You are right that the Earth is not all solid, for starters it has a fluid outer core with a viscosity similar to water, but also, over long time-scales the mantle will flow viscously. The very fact that the Earth is round teaches us that the Earth is fluid.
However, the passage of S-waves through the mantle teaches us that over shorter time scales the Earth is predominantly a solid. P-wave reflections from the inner core have long established that the centre of the Earth is solid, and of course, any sane person will testify that their homes are built on a solid crust (unless they live on a boat!).
Many people consider ice to be the solid form of water, yet over long time-scales it flows viscously and so is really a fluid; however in every day life, for pragmatic purposes, it is often reasonable to treat ice as a solid. The Solid Earth section is perhaps then a misnoma, for pragmatic purposes it seemed easier to describe the Earth as a solid, to distinguish discussion of rocks from discussion of the atmosphere.
Of course, in some problems, like for example mantle convection and plate tectonics, we should be careful with the "solid earth" label. However, a discussion of these phenomena would still be found in the "Solid Earth" forum, although this might appear confusing and somewhat contradictory, there is little else I can do, I don't want to split the forum into too many separate boards at this early stage; unless anyone can suggest a more suitable name to encompass such a broad range of topics from mineral physics to structural geology, the solid earth tag will live on. |
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Baywax
Joined: 23 Jul 2007
Posts: 113
Location: Pacific West Coast
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| Posted: Mon Jul 23, 2007 10:34 pm Post subject: |
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I think Andre is reflecting on the "lava lamp" effect that may explain certain extreme variations in sea level that took place at the end of the pleocene or thereabouts(?)
http://www.sciencedaily.com/releases/2001/06/010619072105.htm
This could also explain the oblong shape of our planet and perhaps the effects of the moon on tides....
The amount of geological activity earths fluidity causes by disrupting the crust could be attributed to this effect.
BTW, what are the chances of the crust slipping on all this magma??? (Yes...... shades of Hapgood..... ewwwww)
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Baywax
Joined: 23 Jul 2007
Posts: 113
Location: Pacific West Coast
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| Posted: Thu Jul 26, 2007 2:31 am Post subject: |
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Sorry if I spoke for you Andre.
I'm just rather excited about all of those humungous cycles and objects... like earth, that we're talking about.
I've got a close friend out on the prairies who says the sun is setting further north than it should be at this time of year. Is this a possibility? If it is then what would contribute to this kind of misalignment? Thanks.
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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.
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Andre
Joined: 21 Jul 2007
Posts: 298
Location: Germany - The Nederlands
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| Posted: Thu Jul 26, 2007 9:49 am Post subject: |
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| Baywax wrote: | Sorry if I spoke for you Andre.
I'm just rather excited about all of those humungous cycles and objects... like earth, that we're talking about.
I've got a close friend out on the prairies who says the sun is setting further north than it should be at this time of year. Is this a possibility? If it is then what would contribute to this kind of misalignment? Thanks. |
Tell your friend that he has a vivid imagination, but no. The rotation axis of the Earth, the motion of the pole, is monitored by the inch as you can see here:
The location of the spin axis wanders a little bit around in the Chander wobble.
Also there is the tilt cycle (Milankovitch) with a period of 41,000 years and your friend is probably not that old. Moreover we are cycling to the upright position which brings the sun to a lower position.
Of course there are some issues with the spin axis of the Earth in the past, forget Hapgood, that's impossible but yet:
| Quote: | Abstract
A new apparent polar wander path (APWP) from the beginning of the Paleocene (65 Ma) to the middle of the mid-Eocene (42 Ma) is shown to be correlated with polar climatic data of the same time period. Rather than applying the classical method based on analysis of site-based poles, we "stacked" the APWPs obtained from magnetostratigraphies. Magnetostratigraphies have the advantage of displaying an unbroken record of local APWPs through time and, for a magnetozone (defined as the a combination of normal and reversed polarity intervals), the instantaneous poles are synchronous. Seven magnetostratigraphies located on 4 different plates covered sufficient time to be used in the analysis. An average APWP was then determined with respect to age at the magnetozone level for the African plate, which was arbitrarily chosen as a reference frame; virtual geomagnetic poles were transferred onto the African plate using ocean kinematic Euler rotations. The calculated APWP is characterized by a loop with two main changes of direction at magnetozones 26–25 ( 61.5–56.5 Ma) and 24–22 (56.5–48.6 Ma) distinct at a 95% level of probability, and indistinct poles related to magnetozones 29–27 (65.5–61.5 Ma) and 21–19 (48.6–40.6 Ma).
We also show that the implied rapid shift of the lithosphere with respect to the geographic pole, possibly an episode of true polar wander, was coeval with the time evolution of vertebrate occurrence on Ellesmere Island (Canadian Arctic) and with the tree ring growth rate in Western Antarctica.
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Moreau M.G. et al 2007 A new global Paleocene–Eocene apparent polar wandering path loop by "stacking" magnetostratigraphies: Correlations with high latitude climatic data Earth and Planetary Science Letters
Volume 260, Issues 1-2, 15 August 2007, Pages 152-165
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Baywax
Joined: 23 Jul 2007
Posts: 113
Location: Pacific West Coast
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| Posted: Fri Jul 27, 2007 4:04 pm Post subject: |
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| Andre wrote: | | Baywax wrote: | Sorry if I spoke for you Andre.
I'm just rather excited about all of those humungous cycles and objects... like earth, that we're talking about.
I've got a close friend out on the prairies who says the sun is setting further north than it should be at this time of year. Is this a possibility? If it is then what would contribute to this kind of misalignment? Thanks. |
Tell your friend that he has a vivid imagination, but no. The rotation axis of the Earth, the motion of the pole, is monitored by the inch as you can see here:
The location of the spin axis wanders a little bit around in the Chander wobble.
Also there is the tilt cycle (Milankovitch) with a period of 41,000 years and your friend is probably not that old. Moreover we are cycling to the upright position which brings the sun to a lower position.
Of course there are some issues with the spin axis of the Earth in the past, forget Hapgood, that's impossible but yet:
| Quote: | Abstract
A new apparent polar wander path (APWP) from the beginning of the Paleocene (65 Ma) to the middle of the mid-Eocene (42 Ma) is shown to be correlated with polar climatic data of the same time period. Rather than applying the classical method based on analysis of site-based poles, we "stacked" the APWPs obtained from magnetostratigraphies. Magnetostratigraphies have the advantage of displaying an unbroken record of local APWPs through time and, for a magnetozone (defined as the a combination of normal and reversed polarity intervals), the instantaneous poles are synchronous. Seven magnetostratigraphies located on 4 different plates covered sufficient time to be used in the analysis. An average APWP was then determined with respect to age at the magnetozone level for the African plate, which was arbitrarily chosen as a reference frame; virtual geomagnetic poles were transferred onto the African plate using ocean kinematic Euler rotations. The calculated APWP is characterized by a loop with two main changes of direction at magnetozones 26–25 ( 61.5–56.5 Ma) and 24–22 (56.5–48.6 Ma) distinct at a 95% level of probability, and indistinct poles related to magnetozones 29–27 (65.5–61.5 Ma) and 21–19 (48.6–40.6 Ma).
We also show that the implied rapid shift of the lithosphere with respect to the geographic pole, possibly an episode of true polar wander, was coeval with the time evolution of vertebrate occurrence on Ellesmere Island (Canadian Arctic) and with the tree ring growth rate in Western Antarctica.
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Moreau M.G. et al 2007 A new global Paleocene–Eocene apparent polar wandering path loop by "stacking" magnetostratigraphies: Correlations with high latitude climatic data Earth and Planetary Science Letters
Volume 260, Issues 1-2, 15 August 2007, Pages 152-165 |
Thanks Andre. I'll have to console my friend. Its those lonesome prairie nights drivin' a man to visit too many websites.
Excellent data you found. Do you think the lava lamp effect could skew our rotation and orbit by much?
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billiards
Site Admin
Joined: 21 Jul 2007
Posts: 81
Location: London, UK
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| Posted: Sat Jul 28, 2007 4:31 pm Post subject: |
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By "lava lamp effect" do you mean convection? The mantle does convect, although it convects so slowly, many many orders of magnitude more slowly than the periodocity that earth spins and orbits, thus mantle convection would not have an effect on our rotation and orbit.
However, momentum transfer in the atmosphere, oceans, and fluid outer core all do have a noticeable effect on Earth's spin. |
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Baywax
Joined: 23 Jul 2007
Posts: 113
Location: Pacific West Coast
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| Posted: Sat Jul 28, 2007 11:54 pm Post subject: |
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| billiards wrote: | By "lava lamp effect" do you mean convection? The mantle does convect, although it convects so slowly, many many orders of magnitude more slowly than the periodocity that earth spins and orbits, thus mantle convection would not have an effect on our rotation and orbit.
However, momentum transfer in the atmosphere, oceans, and fluid outer core all do have a noticeable effect on Earth's spin. |
Very cool!
Here's what the lava lamp effect does to the ocean floor.
| Quote: | "It's a bit like pouring batter onto a hot griddle. As it hits the griddle it sets, and has to run sideways," said UC Davis geologist Charles Lesher, who is not an author on the paper.
The blobs of partially molten rock then flow along the mid-Atlantic ridge, about 90 miles (145 kilometers) below the surface. The molten rock slowly percolates upwards and eventually reaches the surface, where it "freezes" into solid crust. As the ridge pulls apart, it draws out the ends of the "V."
"This provides an explanation for the V-shaped ridges that links the surface features to the Iceland hotspot," said Lesher. |
I think I've overestimated its effect thinking it may be an assymetrical flow with cooler and more liquid spots in the magma causing an assymetical rotation and even possibly contributing to the orbital wobble. I have a feeling this is wrong.
I'm looking for a mechanism that may have knocked us off orbit slightly contributing to a warmer temperature due to a change in proximity to the sun.
The other half of the hypothesis is that the sun may have gained in temperature and radiance and cause us to warm up.
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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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NileQueen
Joined: 21 Jul 2007
Posts: 77
Location: southern Indiana/Cincinnati Ohio
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NileQueen
Joined: 21 Jul 2007
Posts: 77
Location: southern Indiana/Cincinnati Ohio
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| Posted: Sat Aug 11, 2007 4:20 am Post subject: |
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| Baywax wrote: | I think Andre is reflecting on the "lava lamp" effect that may explain certain extreme variations in sea level that took place at the end of the pleocene or thereabouts(?)
http://www.sciencedaily.com/releases/2001/06/010619072105.htm
This could also explain the oblong shape of our planet and perhaps the effects of the moon on tides....
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Beeswax, oblong = rectangular. I think you mean oblate spheroid, where a sphere (earth) gets flattened at the poles and bulges at the equator a.k.a. geoid.
Here is Garret Ito's (featured in your article) homepage. He is in Hawaii.
http://www.soest.hawaii.edu/GG/FACULTY/ITO/
Interesting article Baywax, and interesting research for sure, but no pictures. I want to see what these puzzling V-shaped ridges look like that are puzzling geologists near the ridge that goes through Iceland.
Okay I found the visuals I need in a link on his publication page for 2001
Here is Garret Ito's publication page
http://www.soest.hawaii.edu/GG/FACULTY/ITO/Publications.html
I am VERY interested in how transverse faults form at the mid-
Atlantic ridge and other spreading centers.
As far as pulsating lava lamps etc. yes the mantle, asthenosphere (plastic part of the mantle) --
lithosphere = hard rocky part of earth, which is comprised of the crust plus the upper part of the mantle directly under the crust layer
asthenosphere = the plastic part of the (lower) mantle
--would convect slowly, but can we be sure there are not pockets of softer material? Can molten material from the outer core come up through channels of any sort in the mantle? BTW the magma
at "hotspots" and volcanoes is supposed to be from friction of the plate movement and not come from too deep. Much discussion is going on about mantle plumes and hotspots at http://mantleplumes.org
Can they be that sure that a supervolcano such as Yellowstone not be that deep?
| Quote: | The amount of geological activity earths fluidity causes by disrupting the crust could be attributed to this effect.
BTW, what are the chances of the crust slipping on all this magma??? (Yes...... shades of Hapgood..... ewwwww) |
Well earth is not a layer cake and it is not a jelly sandwich. 
Let's say the crust/mantle moved while the spin axis stayed in place.
How then, would you explain the Hawaiian hotspot? |
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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 12:45 am Post subject: |
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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?
| Quote: | What makes the asthenosphere so slippery and why does it exist on Earth but not other planets? These are some of the key questions that have puzzled Earth scientists ever since plate tectonics was discovered, but only now are the answers starting to emerge. A combination of new experimental techniques and powerful computational theory is enabling scientists to work their way through the asthenosphere atom by atom.
Björn Winker, a mineralogist at the Johann Wolfgang Goethe University in Frankfurt, Germany, believes that the key to the asthenosphere is water. “We have to have water in the asthenosphere to get it plastically deforming,” he explains. This water is no longer in its liquid state, but is bound to oxygen in crystal structures to form hydroxyl (OH-) groups instead.
The question that really interests Winkler is ‘where does the water go’? Which minerals are clinging on to their hydrogen and enabling the Earth to perform its plate tectonic dance?
Unfortunately we can’t get samples from the asthenosphere – no-one has ever managed to drill a hole deep enough. But seismic wave patterns and magma spurting out of volcanoes give us clues as to which minerals make up the majority of the asthenosphere. Winkler finds samples of these candidate minerals on the Earth’s surface and, using specialist experimental equipment, subjects them to the pressures and temperatures estimated for the asthenosphere.
The diamond anvil cell is just one of the tools his group uses. A sample is placed between two diamonds and compressed, to reach pressures of 10GPa – one million times the pressure at the Earth’s surface. When these experiments are carried out at a synchrotron, which provides extremely bright x-ray radiation, he is able to use X-ray diffraction to analyse the way the sample behaves as the pressure is ratcheted up. “It is only possible to make these measurements at a synchrotron,” says Winkler. “Laboratory x-ray sources are far too weak for such experiments.” In other experiments infra-red radiation shines through the sample and makes the O-H bonds vibrate. By measuring how much of the infra-red radiation is absorbed by the sample Winkler can estimate how much water the sample contains and whether it manages to hold onto it as the pressure increases. However, spectroscopic measurements can’t reveal everything. “They can only give you a frequency. It is like trying to figure out a car’s problems from listening to the way it rattles,” says Keith Refson, a colleague of Winkler’s who is based at the CCLRC Rutherford Appleton Laboratory near Didcot in the UK.
Afterwards Winkler and Refson use powerful computer calculations to work out what the atoms are doing and where the water might be held within the structure. “With computer models we can calculate where the sample should rattle and match the theory with experiment,” says Refson.
Already Winkler and Refson have analysed a number of minerals in this way including ‘diaspore’ and ‘clinochlore’. “It was known previously that diaspore would not survive going into the asthenosphere, but we are able to use the knowledge we have gained and apply it to other minerals,” says Winkler. Meanwhile, clinochlore was found to be good at holding onto water, but showed some interesting changes in its structure at around 8GPa. “The nature of the hydrogen bonds start to change and the layers within the structure slide,” explains Refson.
These kind of results have been invaluable for Hans Keppler, a geologist at the University of Bayreuth in Germany. He has been trying to work out why the asthenosphere exists.
Previous theories have suggested that this ‘wet’ and slippery layer exists because minerals leave their water behind them when they melt and turn into magma. “This explains why the asthenosphere appears beneath oceans, but it doesn’t explain why we have an asthenosphere beneath the continents,” says Keppler. Lava continually bubbles up at mid-ocean ridges, but continental plates don’t have an equivalent spring of constant magma. It also fails to explain why there is a lower boundary to the asthenosphere.
Instead, Keppler has been investigating water solubility in the asthenosphere. Using a loaded piston cylinder apparatus he was able to heat and pressurise mixtures of aluminium-saturated enstatite (estimated to make up around 40 percent of the asthenosphere) and water to asthenosphere values. Similar experiments were also done with olivine (thought to make up around 60 percent of the asthenosphere).
What he found was that water solubility in olivine continuously increases with temperature and pressure, whereas in aluminium-saturated enstatite the solubility reaches a distinct minimum at asthenosphere temperatures and pressures. “It means that the mantle minerals cannot contain all the water and the excess water forms a hydrous silicate melt,” says Keppler, who presenting his findings at the 1st EuroMinScI Conference in La Colle-sur-Loup, France, in March this year. The presence of even small quantities of melt in a rock in known to drastically reduce its mechanical strength.
EuroMinScI is the European Collaborative Research (EUROCORES) Programme on “European Mineral Science Initiative” developed by the European Science Foundation (ESF).
The water solubility model explains why the asthenosphere has a lower boundary and why it exists under continental and oceanic plates. Once the aluminium-saturated enstatite passes through its minimum solubility it starts to absorb water again and deeper in the mantle (at higher pressures and temperatures) the mantle becomes dry once more – creating a lower boundary.
Meanwhile, temperatures increase more slowly underneath continents, meaning that the minimum water solubility zone for aluminium-saturated enstatite is not reached until a greater depth under continents, compared to oceanic plates. (see Fig 4 from the Science paper.)
For now the jury is still out on Keppler’s new model. “It is a very elegant, but simplified model,” says Winkler. “Essentially it is based on two minerals, which is definitely not the whole story. The question is, if we refine the theory and include a greater range of minerals will it change things much?”
Some scientists are quite hostile to Keppler’s water solubility model. “It puts a lot of people out of business,” says Keppler. Nonetheless, most people agree that the theory is consistent with what is known about the asthenosphere and that it can’t be discarded. “Only more experiments and calculations can reveal the truth,” says Winkler.
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http://www.eurekalert.org/pub_releases/2007-08/esf-kte081007.php |
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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 12:51 am Post subject: |
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| Quote: | Contact: Carl Marziali
marziali@usc.edu
213-740-4751
University of Southern California
Tectonic plates act like variable thermostat
Heat loss from Earth's interior depends on size and number of plates, says PNAS study
Like a quilt that loses heat between squares, the earth’s system of tectonic plates lets warmth out at every stitch.
But a new study in PNAS Early Edition finds the current blanket much improved over the leaky patchwork of 60 million years ago.
The study, appearing online the week of Aug. 13-17, shows that heat flowed out of Earth’s mantle at a high rate 60 million years ago, when small tectonic plates made up the Pacific basin.
The reason, the authors said, is that much of the heat from the mantle escapes near the ridges between newly formed plates. Those areas are thinner and allow more heat to pass.
The smaller the plates, the greater the heat loss from the mantle on which they float, said geophysicists from the University of Southern California, Johns Hopkins University and the University of Michigan at Ann Arbor.
Several small plates have more area close to the ridge – and allow more heat to pass – than one large plate, explained lead author Thorsten Becker, assistant professor of earth sciences at USC.
“When you go back 60 million years there were a bunch more smaller plates in the Pacific basin,” Becker said.
Using seafloor age reconstructions published last year, Becker and his co-authors found that heat flow out of the mantle in the last 60 million years was greater than previously estimated.
They also found that heat flow is relatively low now that the Pacific basin consists mainly of one large plate. |
There are no undersea vents or volcanoes or ridges there?
| Quote: | Becker added that variations in heat flow would not necessarily affect surface temperature, which depends on many factors, including solar activity and greenhouse gases in the atmosphere.
However, Becker said, a leaky tectonic quilt on average would lead to greater volcanic activity, earthquakes and plate movement. This would affect almost every aspect of Earth’s geography, from sea level to erosion to climate.
“There’s sort of a chain of things that follows from a good mechanical understanding of how plate tectonics works,” he said.
Like previous estimates of heat flow, the new study raises a nagging question. If heat loss for the past few billion years was comparable to Becker’s estimate, the mantle would have had to be impossibly hot at the beginning of Earth’s history.
Becker’s study, which implies an even greater rate of heat loss, shows that previous models designed to avert a “thermal catastrophe” do not work.
“A different solution to the thermal catastrophe needs to be found,” he said.
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Becker’s co-authors were Frank Corsetti, USC associate professor of earth sciences, USC graduate student Sean Lloyd, Clint Conrad of Johns Hopkins University and Carolina Lithgow-Bertelloni of the University of Michigan at Ann Arbor.
Becker is a recipient of a National Science Foundation Early Career award.
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http://www.eurekalert.org/pub_releases/2007-08/uosc-tpa081007.php |
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scpg02
Joined: 22 Jul 2007
Posts: 221
Location: Sacramento
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| Posted: Tue Aug 14, 2007 3:37 am Post subject: |
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| Quote: | | If heat loss for the past few billion years was comparable to Becker’s estimate, the mantle would have had to be impossibly hot at the beginning of Earth’s history. |
But it wouldn't be a steady loss. Woudn't you have to account for the heating caused by large impacts? |
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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 1:34 pm Post subject: |
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And, Maggie, have they taken into account period LIPs? LIP = Large Igneous Province such as Siberian flood basalts (traps)
or Deccan traps in India, and there is one in the North Atlantic. |
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scpg02
Joined: 22 Jul 2007
Posts: 221
Location: Sacramento
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| Posted: Tue Aug 14, 2007 3:10 pm Post subject: |
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I saw a good show that explained the Siberian traps by a large impact on the other side of the globe. Very interesting show.
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