CPT Q. 051: Is sufficient energy available in CPT to melt enough basalt to resurface the ocean basins?

Q. 51. Is sufficient energy available in CPT to melt enough basalt to resurface the ocean basins? – I would like to bring up some energy considerations based on some crude calculations I made using your 1994 ICC paper “Computer Modeling of the Large-Scale Tectonics Associated with the Genesis Flood.” Using your Figure 3 and estimating the total length of the blue cold material at 1.5 times the earth’s circumference, its width as 1/40 the earth’s circumference and its depth as 400 km, and using information in your reference graphs in Figure 1, I estimated the amount of gravitational potential energy available to be 2.58x1028 J. (This included taking a buoyant force into account from the surrounding warmer mantle.) This is a large amount of energy, enough to provide the kinetic energy for the plates and the mantle to move. It would be expected to end up as heat, and probably dispersed through the mantle. Since this much heat would only raise the temperature of the mantle by about 3.5°C (using an average specific heat of 1100 J/kg/K and an average density of 4500 kg/m3), I am not sure why you feel there is a major heat problem. More of a problem, it seems, is the resurfacing of the oceans with basalt, since that requires the latent heat of fusion for the 2 km or so of basalt to be melted from mantle rock for the entire ocean floor, or by my estimation about 8.6 x 1026 J (using 4 x 105 J/kg for the latent heat and 3000 kg/m3 for the density). Although this is still small compared to the gravitational potential energy, it would need to be available at the specific locations of the mid-ocean ridges, instead of spread throughout the mantle, and in the narrow time window when the continents were moving rapidly (about 100 days). Isn’t it unlikely the ocean floors could have been resurfaced within these constraints?

Response: First of all the most glaring energy problem relating to CPT is the rapid cooling required for the new ocean lithosphere that is generated at the mid-ocean rift zones. Not only must approximately 6 km of vertical thickness of basalt be cooled from the molten state to the solid, but some 80 km or so of the mantle must be cooled from the conditions existing near the rift to those characterizing mature lithosphere, which means reducing the average temperature of this lithospheric layer by some 500 K.

A basic concept in heat transfer is that of thermal skin depth, which is given by σ = (κt)0.5, where σ is the skin depth, κ is the thermal diffusivity, and t is time. Skin depth has the following meaning. If one applies a temperature change ΔT to the surface of solid, the skin depth is the depth below the surface to which the temperature change has penetrated after time t. More specifically, in the case of cooling, it is the depth at which the local temperature has dropped by ΔT/e, where e = 2.718 is the base of the natural logarithm, also known as Euler’s number. Let us apply this to the ocean lithosphere. The thermal diffusivity of the rock is on the order of 10-6 m2/s. For this value for diffusivity, we find that after 5000 years, the skin depth for the lithosphere is nnn (10-6 m2/s x 5000 yr x 3.2x107 s/yr)0.5 = 400 m, in other words, less than one km. This shows that the process of thermal diffusion is seriously incapable cooling 80,000 m of oceanic lithosphere in the time available during and since the Flood. To the extent we can be confident that all of today’s ocean lithosphere has been formed by the seafloor spreading process at a mid-ocean rift zone (and I personally believe the case in favor of this conclusion is compelling), then this rapid cooling of the ocean lithosphere is a huge issue not just for CPT but for every serious Flood model.

To address your question directly, the primary energy or heat issue in CPT is not that of heating the mantle excessively. Nor is it in having sufficient energy to produce the 6 km of basalt that today forms the oceanic crust via partial melting of mantle rock. In that regard, the mantle is hot enough on its own to supply this amount of heat with little impact on its overall thermal energy inventory. Decompression melting generally readily does the trick, as solid but deformable mantle rock rises to fill the gap between diverging ocean plates. No, for CPT, the primary energy issue is that of cooling the ocean lithosphere quickly, much more quickly than thermal conduction, with measured values of thermal diffusivity, allows. Some might inquire whether hydrothermal circulation might here come to the rescue. Hydrothermal circulation appears not to be a viable option because the quantity of heat that must be removed to cool 30-80 km thickness of lithosphere by 500 K would vaporize the oceans several times over.