How Solids CAN Convect
Density.
It is density that allows solids to convect within the Earth. As mentioned, in a molten state, it is easier for denser materials to settle out. Just as from ice floating in water, we know less dense material (ice) will float above more dense material (water).
Wild Tangent: Why does water ice float? I think I mentioned this earlier, water is at its densest at 4°C. Still liquid. Below 4°C, water gets less dense and freezes solid. Water ice is only about 90% the density of liquid water. At 4°C, water masses 1000kg/m3 (1g/cm3). Ice is only about 900kg/m3 (0.9g/cm3). You now know why less dense materials will rise within a mass and denser materials will sink. The kilograns measure is for large mass objects, such as planets. The grams measure is used almost exclusively in chemistry. Another fact, water is the only Life solvent that freezes outside-in. All others, ammonia, methane, ethane, chlorine, etc., all freeze inside-out.
Here is a list of the most common elements within the Earth: Lithium, Beryllium, Boron, Carbon, Sodium, Magnesium, Aluminium, Silicon, Phosphorus, Sulfur, Potassium, Calcium, Iron, Nickel. Look up their densities and you shall see FeNi is the densest. It would easily migrate to the central point of gravitation within the mass while in a molten state. And it still took Earth about 4Ga to differentiate to where it is today. Only within the last 1Ga is there evidence that Earth had a GMF strong enough to allow life to complexify and diversify. 4 billion years with no shield. Is it any wonder Life squalored as microbial for so long.
Geologic time, as with astronomical time, are incredibly long periods of time. Remember, there is only one constant: “Change over time”. EVERYTHING changes. That happens to be the ultimate in simplest definitions for Evolution. Change over time.
Also remember that the entirety of the Earth, except LOC, is solid. So how do solids convect within? Virtually all convection within the modern Earth is entirely based on density, heat, and pressure.
Density only determines what will rise or sink in a greatly heated environment. That is all.
Pressure is what ultimately generates all that heat. As material accumulates, greater gravitational attraction. Greater the gravitational attraction, the greater the pressures within a mass. The greater the pressure, the more heat is generated. That is why the SIC is so damned hot. Enough gravitational pressure forces it into a very dense, solid ball of iron. That generates the 4500-6000°C temperature of the SIC. Then, all that heat wants to do is boil and bubble upward. This is thermal conduction. The transfer of heat from a hotter source to a cooler source. One way to think of it, heat radiates, cold absorbs. But that radiation/absorption is entirely subjective and relative.
Wild Tangent: Did you know the water coming out of a nuclear reactor is well above its vaporization point of 373K (212°F, 100°C)? Pressure is what keeps it in a liquid state. Research.
Heat is the main principle behind how solids convect. Hotter material is less dense than cooler material. We have mapped this within molten iron. Even if the material is the same composition. Heat radiates, conducts, AND convects unevenly. The image below shows “idealized” conditions.
Simple Convection Idealized Visualization
The image above should give a good idea how heat is convected. It upwells in narrow columns, unless under a continental land mass such as Africa, then it will spread out unevenly to unevenly sink in elongated sheets. The same phenomenon can be seen on Sol’s surface.
Watch a pot of water as it heats for a boil. With a bright enough light, you can actually see the “shadows” generated by the convection currents, which refracts light, within the water as it curliques about. The same happens within solids, just pitifully slow. Heat makes the solids more pliable, thus more pushable, pullable, risable, and sinkable. Think of them as modelling clay. Solid, but still highly pliable. That is what heat does.
OK. We know denser material will sink while less dense material rises. Look up the densities of the elements I listed above. If one could put all those under enough pressure to keep all molten together, how do you think they would separate into layers? The solids within the Earth work the same. However, that density convection also causes “stirring/mixing” of meterials. That is how rather dense uranium can be found on the surface in certain places. Usually in the form of an ore, a mineral that contains metal that is valuable enough to be mined. Pressurize material enough, and it will melt. Then separate into layers as it cools due to Density. Heated material is naturally less dense. If heated enough, it will actually begin to rise, creating a heat plume withn that layer. Remember the below image?
See that huge heat plume in the left image at about 45°? That is the heat plume going from the LIC/SIC (black) through the Lower Mantle, to the P′ interface, into the Upper Mantle underneath the African continental land mass. In the right image, also at about 45°, is a sinking region within the Lower Mantle. Above, in the Upper Mantle it is my hypothesis that this under the Eurasian continental land mass. Color Ramp: Red indicates hotter, less dense; while blues indicates cooler, more dense. The above images were made from a 100y of seismographs. See how great seismology has become? Sensitive enough we can use seismographs to map the convection within the Earth. Mapping the convection within the LOC/SIC is very difficult, nigh impossible. We need the S-waves to map this convection. S-waves do NOT propagate through the LOC. Thus, the SIC is also blocked. The method is rather complex. I shant try to explain it although I comprehend it. Think spherical trigonometry.
And remember, Africa is quite a large land mass. 7734, the Sahara is actually larger than the 48 contiguous United States. Or damned near, if it ain’t. In fact, globally on Earth, deserts dominate the lands. Something like 42% of all land is arid. Globally.
What thinkest thou of the size of the Sahara compared to the Contiguous USofA?
Two images from Google Earth Pro at the same altitude. Notice the latitude you can kind of draw using northern borders of North Carolina, Tennessee, southern border Missouri, and northern borders of Oklahoma, New Mexico, Arizona. Then you can imagine going on to Pacific. That fits between the Atlantic Ocean and Red Sea shores of the Sahara, with room to spare. I know my geography. It used to be Required Learning when I was in Elementary School and Middle School, then ended after 9th grade in High School. Now I have seen a news program that had High School Seniors and Juniors show on the map of the world where Nebraska was located. The first one went to Southeast Asia. OMdT, indeed.
Remember the gravity-viscosity experiment? Want to know how it truly works?
The steel ball is much denser than even frozen butter. Probably at least 6× denser. The downward pressure generated by gravity and density actually produces minute amounts of heat from the pressure. This causes the butter to become more viscous, but still solid, allowing the steel ball to convect downwards. Sink. Both remaining solid the whole time. That is how the Density-Gravity-Viscosity-Pressure thing works in the convections of solids. Pushing. Squishing. Squeezing. Through, past.
Wild Tangent: Did you know that within thermodynamics, anything >0K radiates heat? That is why “cold” is entirely relative. Subjective to each indiviual person. What may be “cold” for you, may be “warm” for me.
T…H…I…N…K…
You see that crap all the time in winter. Some people bundled more against the cold than others. It is obvious as your nose.
Heat is the main principle that drives convection. Differences in density will cause uneven distribution of heat outwards. Earth today would probably be “frigid” compared to the Earth in the Archaean Period. T…H…I…N…K… about that.
During the Hadean Period, when the Earth had a rather severe case of flatulence, if there was solid rock to stand on, it would have been warm enough to melt soles. The air temperature probably about 180+°F (82.2°C, 355.372K)
BTW: OMdT = O! My God-Thing.
— The Unknown Atheist
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