Does Magma Exist?

This is part of a series of articles responding to the claims made in Dean Sessions’ Universal Model.  Click the link to see the introduction to the series.

In Universal Model vol. 1, ch. 5, “The Magma Pseudotheory,” Dean Sessions is on a mission to disprove the existence of magma.  (You can’t have a “hydroplanet” with a core of ice if it gets hotter toward the center.)  To convince himself he has accomplished this, he performs his usual routine of misstating the actual scientific theory, disproving the fake theory he just made up, and then announcing that it all fits perfectly with the UM.  No, it doesn’t.  Oh, and he keeps forgetting about convection.

“Magma,” in geological parlance, means molten rock that exists below the Earth’s surface, whereas “lava” is the same thing after it is extruded out of a volcano.  Dean Sessions knows about volcanoes, and he knows that lava must come from under the ground.  So magma exists, right?  Well, okay, but Sessions wants to make it clear that he doesn’t think molten rock forms below the crust of the Earth, so he renames “magma” in the crust as “intrusive lava”.  Regular old “lava” becomes “extrusive lava.”  The term “magma” he reserves for the “only… theoretical molten rock that geologists think is generated in the layers below the crust” (UM, vol. 1, p. 70).

Magma is a “pseudotheory,” according to Sessions, because pseudotheories are false theories taught as fact.  It’s just a theory because we can’t drill holes down into the mantle and core of the Earth to directly examine what’s there.  Instead, we just have to “infer” what’s there by indirect means.  (You know, like we have to “infer” the existence of oxygen molecules by indirect means because we can’t shrink ourselves down small enough to look at them, and even if we could, our eyes wouldn’t work unless they were tuned to X-ray wavelengths, and so on.)

All Sessions has to do to show that deep magma is taught as a fact is to quote one geologist saying the opposite.  “Magmas properly belong to the realm of theoretical petrology…. [T]hey cannot be examined in the field, collected, studied or directly experimented with” (UM, vol. 1, p. 71).  Oh, wait!  That wasn’t the part that proves Sessions’ point!  It’s two pages later in the quoted text, where the geologist says, “There is, however, irrefutable direct evidence that materials with the physical properties of magma exist within the Earth.”  See?  How can there be direct evidence for magma if you can’t directly experiment with it?  Oh, wait!  Maybe the geologist was referring to the fact that we can detect substances that have the mechanical properties of molten rock by mapping how seismic waves travel through them.  Or maybe he was referring to the fact that we can sometimes drill right down into an underground magma chamber, and find it there… you know… underground.  I can hear the UM Team objecting that Dean Sessions knows quite well, thankyouverymuch, that molten rock exists in the crust (“intrusive lava”), but he was talking about “magma”–hypothetical molten rock below the crust.  Of course, if the quoted geologist was using the standard geological definition of magma as “underground molten rock,” he really wasn’t contradicting himself.  It’s only a problem if he was using the definition Dean Sessions made up.

Well, whatever.  The MAIN point is that Dean Sessions can also quote a bunch of other geologists (pp. 70-71) carefully specifying that they don’t know everything about what’s in the deep Earth, which just goes to show that they don’t know anything, right?

But those pesky geologists persist in believing that they do know some things about the Earth’s deep interior, such as that it must be really hot down there.  He quotes one geophysicist, “The interior of the Earth is clearly hotter than its surface, as shown by volcanoes and the temperatures within mine shafts” (p. 74).  In other words, we know it must be hot down there because hot stuff comes shooting out the surface from time to time, and because when we dig holes it gets hotter as we go deeper.

Sessions claims he can prove the geologists wrong by doing what the scientists should have been doing all along–making sure scientific theories conform to actual observations, instead of just assuming their theories are true.  Sessions points out, for instance, that the way heat escapes from the Earth is exactly the opposite of what the “Magma Pseudotheory” predicts, but it does follow what should be the case if the heat to melt rock is generated in the crust through frictional heating along faults, and kept going by tidal forces.

In reality, Dean Sessions just doesn’t understand what he’s talking about, and he is unable to recognize it when data do not conform to his ideas.  

He begins on p. 92 by showing us a U.S. Geological Survey map of the thickness of the Earth’s crust, which clearly shows that the crust is much thicker on the continents than the ocean floor.  He then uses the USGS map to make his own map of what the “Magma Pseudotheory” should predict, by assuming the heat flow through the thicker parts of the crust is less than through the thinner parts.

In the Magma Pseudotheory, heat coming from deep inside the Earth transfers to the surface through convection currents from the inner core toward the mantle and ultimately to the crust. It is then conducted to the surface, through the Crust. The flow of heat should be easily predicted and follow known patterns of heat transfer if the Earth’s heat is actually coming from magma.   (p. 91)

Here’s how he explains the heat transfer theory he’s using.

The physics of heat flow tell us that heat travels or flows across a gradient from hot to cold and that the flow will be greater when the gradient is steeper. In other words, more heat flows from hot toward cold than flows from hot toward warm. The bottom of the ocean, at around 2 °C (35 °F) is much cooler than the surface of the continents, which averages approximately 14 °C (57 °F). Because of this, we should expect heat flow to be greater through the oceanic crust than through continental crust. Note that we are not referring to why the surface of the Earth is warmer than the bottom of the ocean-that is primarily due to solar heating. We are considering the flow of heat through the crust.  (p. 92)

However, Sessions also produces (p. 92) another USGS Map showing actual measured heat flows around the globe (see below), and announces that they are totally different.

The greatest concentration[s] of heat… land on plate boundaries where gravitational frictional heating is highest…. This demonstrates unequivocally that the Earth’s heat flow through the crust cannot originate from a theoretical magma heat source beneath the crust, confirming the Frictional Heat Law and the Gravitational Friction Law.  (p. 92)

Well, actually… if you look at the “actual heat flow” map, it’s clear that the highest flows are not at all plate boundaries.  (Many plate boundaries appear to have quite low heat flows.)  Rather they are at mid-ocean ridges, which are only one kind of plate boundary.  These plate boundaries are where real plate tectonic theory (as opposed to the Magma Pseudotheory, whatever that is) says hot, plastic, solid material (NOT MAGMA) wells up from below in convection currents, pulling apart the overlying lithospheric plates.  When the overlying lithosphere cracks apart like that, it lowers the pressure on the rocks below in the mantle, lowering their melting temperatures, so that some minerals melt and the magma creeps up through the cracks.  So in reality, divergent plate boundaries are EXACTLY where conventional plate tectonic theory implies the greatest heat flow should be, because of convective heat transfer.

When Sessions used his simple conversion of crustal thickness to expected heat flow, he had to implicitly assume that the material below the crust has a uniform temperature all around the globe, and that no hot material is transported up through the crust.  In other words, he must have forgotten that he just said the hot material was supposed to be transported around the interior in convection currents.  In convection currents, hot material flows upward in certain places because it is less dense than the overlying cooler stuff.  When it reaches the top it spreads out to the sides and cools, while the cooler stuff at the top sinks down to the bottom and heats up.  This goes on over and over, as illustrated in this animation.

Geophysicists have not been able to explain why heat flow through the thin oceanic crust is less than the heat flow through the thick continental crust. The thicker and more insulated continental crust areas should have a significantly lower amount of heat flow whereas the thicker continental crust should theoretically be cooler than oceanic crust because of the distance from the heat source as predicted within magma theory. (p. 92)

Wait… look at that figure again.  On average, at least, the ocean floors do show higher heat flow than the continents, and in fact geophysicists estimate that the average heat flow from the continental crust is 65 mW/m^2, whereas the average heat flow from oceanic crust is 101 mW/m^2.  Why is Sessions now saying that there is less heat flow through the oceanic crust?

Sessions explains on p. 93 that since the continental crust is about six times as thick as the oceanic crust, then the heat flow through the oceanic crust should be six times higher.  Conductive heat transfer is proportional to the thermal gradient (how much the temperature changes with depth) and the thermal conductivity of the material (how efficiently the material transmits heat by conduction), so assuming that the thermal conductivities of the oceanic and continental crust aren’t that different, the thermal gradient in the ocean crust should be steeper than that in the continental crust.  Next Sessions produces a quotation from an old Scientific American article saying that the thermal gradient in the ocean crust is about 15 °C/km depth, whereas that of the continental crust is about 25 °C/km, which is seemingly the opposite of what we would expect.

The answer to this conundrum is, once again, that Dean Sessions forgot about convection.

The oceanic crust is under the ocean, after all, so lots of water gets down in the rocks and is heated up, causing convective flow.  (NOTE:  Even Sessions agrees that it gets hotter with depth within the crust, so this should not be controversial.)  This hydrothermal flow actually increases the heat flow out of the interior, but simultaneously decreases the thermal gradient of the upper oceanic crust.  In a convection current, hot stuff does flow toward the cooler areas, but cool stuff also flows toward the hotter areas, so the relationship between the thermal gradient and the heat flow is more complicated than with heat conduction.

Heat flow estimates like those plotted in the figure above are not measured directly.  They are measured indirectly via thermal gradients.  If essentially only heat conduction is going on (like in most of the continental crust), then you can just measure the thermal gradient in boreholes, estimate the thermal conductivity of the rocks, and back out the heat flow.  If you know hydrothermal convection is going on, then you have to make corrections for that.  And geophysicists do.

So now it all makes sense through the lens of standard plate tectonic theory, even if we don’t have all the details worked out.  There is greater heat flow through the oceanic crust than the continental crust because ocean crust is thinner, because hot material is welling up at mid-ocean ridges, AND because of hydrothermal circulation under the ocean floor.  The thermal gradient in oceanic crust is lower than that in continental crust because hydrothermal circulation also reduces this gradient, while increasing heat flow.

Does it make sense within the UM?  Not really.  The UM predicts that you should have high heat flow at all kinds of plate boundaries, because the heat is generated by earthquakes.  So why don’t we see excess heat flow in areas where tectonic plates are causing continental lithosphere to collide (like in the Himalayas)?  There are lots of earthquakes there, after all.

In fact, Sessions is beset by the same problems as regular scientists.  That is, we can’t drill all the way to the center of the Earth to see what’s there.  So why should we believe that the Earth is cold in the center (as in the UM), when from what we CAN see it gets hotter and hotter toward the center?

Get ready for it…

Sessions says (p. 94) that the Earth appears to heat up too rapidly with depth.  He quotes a geophysicist from the 1930’s saying that “If the gradient determined [near the surface] should continue downward unchanged, the temperature at the center would exceed 350,000° F” (p. 94).  Sessions then goes on:

No one thinks the center of Earth is thousands of times hotter than the surface of the Sun. How can heat be so high in the crust and still be thousands of kilometers from the source of heat, residing at or near the core? This too-hot-too-fast problem just does not follow the physics of heat flow.  We would likely boil away if the Earth’s geotherm followed the assumed gradient of the magma model pseudotheory.  A temperature of 350,000″F at the core just does not work for any theory!  (pp. 94-95)

This objection would be correct… if convection were not going on in the mantle.  That’s right.  He forgot about convection again.  Remember how you can actually get more heat flow through convection, with a lower thermal gradient, than when there is only thermal conduction?  Once again, Sessions has disproved a prediction the standard theory does not actually make.  Here is what the temperature profile of the Earth is supposed to look like according to the standard theory.  Note how the gradient is lower in places like the atmosphere, mantle, and outer core, where lots of convection is supposed to be going on.

There’s really nothing left of the UM argument.  Oh, maybe some geophysicists didn’t get the thermal gradient they were expecting in the odd borehole somewhere, or whatever, but that doesn’t cancel out the thousands upon thousands of other measurements that show steadily increasing temperature with depth.  Sessions can complain all he wants about how geologists don’t know everything about the deep interior of the Earth (a fact geologists readily admit), but 1) he doesn’t either, and 2) none of the evidence that does exist supports his ideas.