Heat release from tectonic friction

Frictional heat dissipation isn't necessarily a problem for heat budget problems because once you initiate melting slip efficiency will increase. You could look at this in detail using realistic rheologies (flow laws for rocks under stress) with all sorts of dependencies which theoretical geophysicists like myself are very interested in, but this doesn't really matter in our case.Heat is, to me, probably the most obvious problem inherent to any young earth hypothesis. The heat problem is (at least) two-fold: (a) radiogenic heat (most heat producing radioisotopes are concentrated in continental crust) and (b) the conductive cooling of oceanic lithosphere.I'm on vacation now so I'll just do a quick calculation focusing on the latter problem, which happens to be close to my research specialty. The thermal structure of oceanic lithosphere is, to first order, extremely well understood. The main idea is that we know that oceanic lithosphere is formed at spreading centers, migrates away and cools. Observable consequences of cooling are things like surface topography, surface heat flow, potential fields (gravity, geoid), and tomographic methods (mostly in seismology), so models can be well constrained. A very rough approximation of the heat content removed from exposed oceanic lithosphere is about 9*10^28 Joules, which comes from cooling the upper 100 km of the mantle below oceans (~3*10^19 m^3) by about 700 K with a volume heat capacity of about 4*10^6 J m^-3 K^-1. This is close to a quick integration of seafloor heat flow for a detailed lithospheric cooling model I have developed. I get about 8.4*10^28 J.We can probably consider this a lower bound since you will have to account for a far more than currently exposed seafloor given the record of tectonic motion and subduction, anyway.This amount of heat is enough to heat the oceans by about 14300 K (mass=1.4*10^21 kg, specific heat=4200 J/kg/K), or boil an ocean 140 times more massive than Earth's.If you want to release heat over the course of a year, the average surface heat flux over that time would have to be about 3*10^8 terrawatts. Released over 1000 years the surface heat flux is about 3*10^5 TW. This can be compared to the present day seafloor heat flux of about 30 TW or the solar heat flux of about 1.7*10^5 TW.I hope I haven't made any mistakes.

The energy released from reducing the velocity of the mass of the oceanic and continental lithosphere (~2.5*10^23 kg) from 0.3 m/sec to 0 m/sec is about 10^22 J. Although this is a large amount of energy which almost certainly should have left a signature in geophysical observations, this could be dissipated over a large volume in the mantle by viscous forces (not released into the oceans) and is about 7 orders of magnitude less than heat content removed by lithospheric cooling.

I calculated the energy dissipated by reducing the velocity of the lithosphere assuming all of it goes into heat. Where this heat is dissipated depends on where the resisting forces are. We could consider this resisting force to be friction along interfaces, but heat dissipated will quickly generate melt, reducing friction and thus the resistance to slip. Thus, you can't dissipate this much heat along thrust faults that quick. The most 'reasonable' expectation would be that mantle convection and subduction loses power and is stopped by the increasing rigidity of the mantle (e.g., Baumgardner's runaway model). Thus the 'frictional interface' wouldn't be localized and could be distributed throughout much of the lithosphere and asthenosphere.

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Those are al resistive forces.
You are trying to calculate all the possible Forces that resist the motion.

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The energy that it takes to move the weight of the plates through the distance of whatever is the case, over a period of unit time ought give us the answer, right?

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E = 1/2mv^2?

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Yes, this is the formula I have used. The distance is only important inasmuch as it is related to velocity.

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It seems the main difference in our numbers is that you accounted for cooling of the entire seafloor 100km deep. I assumed that the majority of the seabed would have been cooled prior to the flood, maybe it was created cooled off?

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The trouble with that is that the thermal structure of the Earth is a fossil of transport processes, the history of which can be constrained to impressive precision by observation and experiment. An analogous hypothesis with similar credibility is the suggestion that the universe was created last thursday in the form that we remember.

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I am not sure that heat from below maybe 10km would actually be absorbed into the ocean though? Wouldn't it be more likely to go into surrounding rocks? But even if only half of the heat made it to the oceans it would still raise the temperature by 7,000K.

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Well it is precisely the 'surrounding rocks' which are cooling. Here is a 2D (average transect with age) tomographic inversion for upper mantle temperature over Pacific oceanic lithosphere as a function of lithospheric age: http://ciei.colorado.edu/...piro_research_files/image003.jpgThis thermal structure is clearly a consequence of gradual conductive cooling of the upper mantle with age, corroborated by many other geophysical observations in addition to seismic tomography. No other physical mechanism can account for these observations.

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I am interested in your thoughts regarding this portion of the problem. In order for the plates to move at the proposed speed, the mantle would have to have convection currents that increased proportionally. Theoretically this heat could come from a rapid acceleration of radiogenic decay rates (a favorite of creationist theories). Would it theoretically be possible to produce such convection currents? What kind of heat differential would be required?

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Well, the major heat producing radioisotopes are strongly concentrated in continental crust, so for every 1 K increase you might get from mantle radioactivity, you might increase the temperature of continental crust by 1000 K. Continental crust would expand into vapor long before the viscosity of the mantle decreased significantly. The magnitude of heat produced by accelerating radioisotopic decay is similar or larger than that transported by cooling oceanic lithosphere.If you could explain the geology of the Earth simply by granting accelerated radioisotopic decay, I might have still been a creationist. In reality, it explains nothing while itself generating an endless list of extraordinary problems in the most basic subjects of tectonophysics.

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I suggest the way to attack the heat problem is to calculate the average current heat flow from the earth and project that 4.5 ga into the past (this would be a minimum number since the heat flows of the distant past were certainly much higher - so we are only getting an end-member here).

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Okay, now compress that amount of heat into 6ky and see what happens.

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By the way, I'm not so sure that your statement about where the heat-forming radioelements are found is correct. While many of the elements are found in continental crust, where we can extract them, there is some consensus that the core is another concentration of radionuclides such as thorium and uranium. After all, what causes heating of the mantle plumes?

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The exercise of constraining the thermal history of the Earth given known present-day surface heat flow has been the subject of much interest in geophysics for a long time, and happens to be a major interest of my own. The primary factors which present difficulties for such calculations is the uncertainty in bulk Earth concentrations of the major heat producing elements, the fraction of surface heat flow originating in radiogenic sources in continental crust, and uncertainty in scaling laws for temperature-dependent rheology of the mantle (as temperature increases, viscosity decreases). The last of these has been given much more attention than the first two probably because a solution to this problem is a critical commentary on the fundamental nature of mantle convection.Incidentally, it should be of great interest to creationists that a long known problem with mantle viscosity scaling laws is that conventional scaling with conventional constraints on the present-day cooling rate of the Earth (around 50-120 K/Gyr), extrapolation into the past results in an exponentially increasing cooling rate of the mantle, until the whole mantle essentially melts. You need to go back in time at least a billion years to arrive at thermal catastrophe, but I'm sure YEC's like Baumgardner and Snelling would still jump all over this. Nevertheless, the conventional scalings are very simplistic and certainly wrong for many reasons related to coupling behavior of lithosphere and mantle and the like. I've just submitted a paper showing that the surface heat flux over seafloor is about 10-25% lower than conventional estimates, significantly changing an important boundary condition for thermal history calculations. In addition, I am in the middle of investigating a coupled thermal evolution and isostatic model of the Earth to estimate eustatic sealevel changes from present-day to the Archean. I should be able to show that the thermotectonic behavior of oceanic lithosphere (e.g. plate velocity) is not compatible with conventional scalings.Nevertheless, while I can't do the calculation now, the convective scaling doesn't matter for the young-earth hypothesis because even if the Earth were completely melted convective transport will not be able to transport nearly enough mantle heat and is irrelevant for transport of heat generated in continental crust.Finally, you doubt my comment on the concentrations of the major heat producing radioisotopes. First, I compared the concentration of radioisotopes in the mantle and continental crust, which I don't think is contrary to prevailing thought. Second, my understanding is that the consensus regarding concentrations in the core is that thorium and uranium almost certainly do not have an elevated concentration (they are strongly lithophile even at high pressure/temperature), but the jury is still out on concentrating potassium. Nevertheless, it is not clear if such a concentration in the core is necessary. It is known that at least some heat (something like 5-11 TW) must originate in the core to drive the geodynamo and maybe (a big maybe, in my opinion) drive mantle plumes, but this does not require radiogenic sources. Release of latent heat and gravitational potential energy associated with inner core growth might be enough. There are also mineral physics problems associated with estimating thermal core-mantle interaction because the thermal conductivity across D'' is not well understood.Anyways, the point is that since radioisotopes are preferentially concentrated in continental crust, the crust will be melted and vaporized long before the mantle temperature changes significantly from accelerated decay.Edited by TrueCreation, : No reason given.

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Unless you have a number as an answer...

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I have already estimated the heat released by cooling of (presently exposed/active) oceanic lithosphere in Message 25 as on the order of 10^29 J. Then, in Message 28, I estimated the heat released from slowing plate tectonics from 0.3 m/s to 0 m/s as on the order of 10^22 J. Obviously the first number is more important for YEC's because it is far greater and, unless you want to appeal to magic, must be transferred through the oceans. Do you dispute this?Edited by TrueCreation, : No reason given.

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Dispute is the wrong word.

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I tend to believe your figures of 10^22Joul, because it seems straight forward and simply physics.

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I am not so sure of "estimated the heat released by cooling" because there seems to be too many mitigating factors that must be estimated or inferred.

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Of course, if this were important to me as it seems to be to you who are writing a paper on the matter, more attention to your mathematics and deductions could convince me, I am sure.

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But if the two numbers were closer, the cooling would essentially be a double check against the mechanical energy, which I tend to accept based on the confidence in your physics for E = mv^2/2.

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Well, it should be of interest to you because explaining the first-order thermal state of the upper mantle is pretty much the most basic and informative observation in all of plate tectonics.The two numbers are not close because cooling is a transport of internal energy, whereas the mechanical part is a transfer of kinetic energy. The gradual migration and cooling oceanic lithosphere with distance and age from spreading centers is one of the best established processes in all of geophysics since the observations which constrain it are simple and massively corroborated by different field observations and experimental constraints on the actual properties of the Earth. There are lots of uncertainties, but the uncertainties change results by percent, not orders of magnitude, let alone six orders of magnitude.A pretty good introductory survey of the problem is here:http://topex.ucsd.edu/geodynamics/07cooling.pdfAlso consider this page by Joe Meert, who addresses the problem of explaining seafloor topography (since it is related to the temperature of oceanic lithosphere) for YEC's:THE DEPTHS OF THE OCEANSAlso, you can take a look at a recent paper I published here:Dropbox - 4xxI use numerical techniques to solve the cooling problem, which is, at least to me, far simpler than analytic techniques, especially when you introduce certain complexities like temperature-dependent heat transport properties.

Mantle convection is driven by thermal buoyancy forces which originate in cooling at the surface, not a different mechanical source. Unless the Earth contracts or is acted on by an external force, kinetic energy available for plate tectonics at the surface originates in a conversion from the internal energy by mantle convection.A nice comprehensive review-style paper of some of the fundamentals of the thermodynamics of the Earth is given by Jaupart et al here:http://perso.ens-lyon.fr/...PDF/JaupartLabrosseMareschal.pdf

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There happens to be enough water in the lithosphere, asthenosphere and mantel to fill our oceans 7 times. That water had to get there some way, and sometime in the existence of the Earth.

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You're right. Although, perhaps a more useful question is why the water remains there. How it got there may be more of a cosmochemical question, although we know that at least some water is continually carried into the mantle by subduction. But why it remains there and is not completely degassed is a geochemical one. There is a lot of water (albeit in low concentration) in the mantle simply because water is soluble in major mantle minerals like olivine and pyroxenes at most mantle pressures.I don't see what your point is, though.Edited by TrueCreation, : No reason given.

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Isn't water the the cooling agent that cools the plates as they move?

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So my point is that the water would have got in the materials between the stationary materals and the moving materials during the movement, and into the mantel during any subduction.

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God Bless,

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Water is able to cool things by moving through it. Chemically bound water in the mantle won't accomplish any of that. On the other hand you could suppose that hydrothermal circulation in oceanic lithosphere removes heat and cools the lithosphere. In fact, we already know this happens in oceanic crust and to some extent in the mantle, but it is not more widespread than we would expect from present-day rates. Most heat is transported by hydrothermal circulation very close to spreading ridges where the lithosphere is mostly oceanic crust and is thin, but after a few million years of cooling thermal gradients at the surface are not enough to drive circulation and pore spaces are sealed by alteration processes like serpentinization. The lithosphere would be chemically and thermally nothing like what we see if cooling by seawater transported 10^29 J of energy, and none of this solves the heat problem anyway.Nevertheless, you are right that water in the lithosphere will be dragged into the mantle during subduction, which is well understood. This is why volcanism occurs in subduction zone arcs (think of the 'ring of fire'). On the other hand, note that this water taken to the mantle is chemically bound in serpentinites and such. Free pore water is mostly squeezed out of the plate long before it reaches significant depth.Edited by TrueCreation, : No reason given.

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Oh, I get it.
Its like spagetti moving in a boiling pot as the salty water bubbles, right?

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The bubbling energy is there all the time.
The qustion the OP asks then seems to guess what the temoerature would be to mive the spagetti faster than say 600 million years, and form Pangea in 4000 years.

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If the YECS wold entertain Pangea as a theory, the whole point of the question woulkd be moot.
But, supposing that they did accept a 600 million year duration, compacted into 4000 years, your calcuklations would expect the thermal energy of the moment to raise the present temperature.

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Is that what we are saying here?

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I think so. In the "spaghetti pot" of the Earth, the kinetic energy of motion is small compared to the huge amounts of heat removed by conduction at the surface of the boiling water/convecting mantle.The general point is that an understanding of geology and geophysics tells us that if the YEC hypothesis is true, the only way to make it work is to take the long history of the Earth and compact is into the younger timescale. The specific point I make in this thread, as you seem to correctly ascertain, is that if you do this one of the major problems is with heat. It is like witnessing a car crash--was the car going 100 kilometers per hour when it hit the brick wall, or was it going 30,000 kilometers per second? The latter causes a big heat problem, but we could also study the wreckage and find that no such speed was ever reached. Maybe the car was going 80 kph or 120 kph, but it certainly wasn't going a good fraction of the speed of light.

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Any water at the bottom of the ocean that was introduced into the oceanic crust would be able to account for a lot of cooling as it is 1.5C to 4.5 C.

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But water at 210 can still transfer heat as it becomes steam, as well as superheated steam. And yes the water in the lithosphere and asthenosphere would need vents to expell heat such as those in the ocean and through volcanos, as well as the cooler mass above the water.

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The temperature needs to be much higher than 200C for steam to form at depth in oceanic crust, let alone the mantle. In any case it doesn't matter much. Hydrothermal circulation in oceanic crust is a topic of much interest in geodynamic modeling. The kind of Nusselt numbers (convective/conductive heat transport ratio) for hydrothermal transport in the youngest oceanic crust are on the order of 10-100. You need to assume nonsense thermodynamics to significantly increase this number.

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And yes the water in the lithosphere and asthenosphere would need vents to expell heat such as those in the ocean and through volcanos, as well as the cooler mass above the water.

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I don't see how they "need" vents to expel heat except as an ad hoc mechanism (which doesn't work and is not compatible with geochemistry and petrology) to transport an enormous amount of heat from the lithosphere into the oceans, which then needs to be magically removed anyway. Also, I hope you aren't confused: the water in the rock of the lithosphere and asthenosphere is very small and will not contribute to cooling.

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How did that water get captured in the lherzolite and retained in nominally anhydrous minerals?

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Where did that water come from?

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Initial accretion of Earth and subduction over 3 or 4 billion years of Earth history.I don't know what you are trying to say in the other part of your message.

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Yeah, I see the point,...
The problem seems to be informingthe YECs that Pangea happened 600 million years ago, though, so we can do the math.

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I don't know if they will deny Pangea, but how could they accept it if the earth is only 6000 years old??

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Or, maybe they do accept Pangea but think it happened around 6000 years ago?
If so, your case has merit in informing them it just could not be.

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But there is NO hope this will change minds, since the atheists on the other side ar just as bad when they hear that Pangea supports Gen 1:9.

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Nobody wants the truth if it doesn't conform with their opinion.

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Well, convincing someone of a certain truth is not my concern if they do not value scientific method. I might go so far as to say that if one does not value scientific epistemology, they deserve to believe lies.