Two things:
1. The HEAT will only start to decay exponentially when the
fuel is depleted and the earth is just radiating heat.
Just like your example of the open oven. If the heat is still on the oven will
not cool.
2. The fuel is still in the process of being consumed. Indeed radioactive decay is an example of
first order rate kinetic and does decay non-linearly. HOWEVER, the decay is in the presence of the parent isotope. Many of the parent isotopes give rise to radioactive daughters which, themselves, decay along a different first order curve. But indeed the fuel is being consumed. Just as when we turn on the oven and use up electricity we are consuming the coal that makes the electricity. That doesn't mean YOU can measure the amount of "decay of coal" by tracking the temperature in your oven over 15 minutes while it's on. Do you get this point?
Now, we
know for a fact that radioactive decay of elements in the earth is going on and causing heat. There is a
measured geothermal gradient and we know quite a bit about the mineralogy of the mantle and, owing to the presence of p and s-wave shadow zones and travel times measured daily all over the globe, we know approximately what state many of these zones are in, be they liquid or solid or "plastic". Kimberlite pipes and other "windows" into the mantle give us some idea of the pressure and temperature regimes (as evidenced by the mineral assemblages present) down deep.
ALL THAT leads us to the conclusions that the deeper you go into the earth the hotter it is. Indeed it is
still hot down there. Like the open oven that is still on, we have fuel keeping the processes running.
You've been shown ample evidence that the
plates are still moving so where is the mystery? Why make claims that are not supported by the evidence?
If you think the plates were whipping around much faster in the past, then please explain the dating/distance curve from the Hawai'ian island chain or the magnetic anomalies around the spreading centers.
Do you not believe there are radioactive materials in rocks? Do you not believe in Uranium, Thorium or K-40?
If you would like,
HERE is a discussion of some of the details around heat flux and geothermal gradients.
Radiation is a fact of life with rocks. It may not be that you will be immediately radioactively poisoned by going up to a piece of granite but it is likely to contain a certain amount of radioactive material. Look at the little pink minerals. Those are a mineral called
orthoclase and it has the chemical formula KAlSi3O8, that K is a give away there. About 1 in 10,000 atoms of potassium is K-40 (approximately), and that's radioactive. In addition Uranium likes to hang out in "felsic" igneous rocks. It's part of the chemistry of this element and these rocks. That's why pegmatites which are even more "felsic", often contain abundant uranium minerals. In addition there are a number of other naturally occuring radioactive elements that are in various igneous rocks and in the magma that makes them, as well as sprinkled throughout the earth in other rocks.
The point being that while an individual chunk of regular rock may not be radioactive enough to melt another rock, the whole of the mantle of the earth plus the "insulative" properties of the huge mass of rock that is the earth, helps to provide enough heat to do the job.
There's no magic there. It's a matter of scale and interacting effects. There isn't a mystery to my knowledge.
I'm not a specialist in radiogenic isotopes, but I do know enough to understand why some cities that are built over large concentrations of certain types of rock have a
radon problem in their homes (
LINKY).
Well, it certainly has all the hallmarks:
1. Oversimplied to the point of cartoonish.
2. Ignorance of any underlying "detail"
3. Presupposition of an outcome
Yup, I bet it
is a new evidence of creationism!
Except we do see the plates moving daily and we see Mt. Everest still growing at about 3cm/yr (
SOURCE)
.