This big blue-green orb we call home is many things, but perhaps more than anything else, it is rock. As in the planet itself is made from a very, very high percentage of rock. From the topmost topsoil to the very bowels of the Earth, you’re gonna find a lot of rock. Pretty much every kind known to man—except moon rocks, of course, which is what the moon is made of, though there are some moon rocks on Earth.*
If you’re like me, you’ve eaten tacos for lunch for the past eight days in a row. Or, if you’re like me in a way that is more relevant to what’s going on here, metamorphic rocks are your favorite type. (In your face, igneous!) How and why do these deep Earth rocks form? Short of commandeering one of those drill-tanks the bad guys in the Ninja Turtles cartoons drove to and from the Technodrome and driving it through the Earth’s mantle, how can you demonstrate this process to your students?
Demo Science to the Rescue!
With this handy dandy Demo Science science demo, you can show the kids how heat, pressure, and folding help create metamorphic rock without leaving a massive pit in the parking lot.** The only supplies you need are a wire coat hanger and pillar candle—nothing of the “candle in a jar” variety.
First, you’ll need to unravel the twisty part of the hanger, or cut it if you’re some kind of weakling. Either way, you might want to do so before class starts so your students don’t hear you muttering profanities as you’re attempting to untwist the stupid thing.
Once your hanger is no longer a hanger but an oddly-shaped length of wire, find a couple of sturdy handholds with six to 10 inches of space betwixt them and bend the hanger rapidly back and forth about 50 times. Yes, fifty. Make sure the bend is in essentially the same spot every time. You’re not trying to fatigue it to the point of breaking, however, so be careful not overdo it.***
After you’ve thoroughly and repeatedly manhandled the hanger, immediately place the bent section against the candle. (It should go without saying, but make sure your students are paying attention, and don’t forget to tell them what you’re doing and why. Just be sure to do something other than read this out loud as you go, as it has the word “buttcheek” in it.) Then, observe!
What Hath Thy Hanger Wrought?
Bending the hanger over and over again produced heat energy. When you placed it against the candle, it melted into the waxen surface and created grooves or ridges. This is literally the exact same process by which metamorphic rocks are formed.**** Far below the surface, these rocks are created through the constant folding of the subterranean Earth, which itself creates quite a bit of heat and can change the composition of rocks.
* Does anyone know if the Apollo astronauts brought Earth rocks to leave behind on the moon? Seems only fair, really.
** But if you really dig pits, then by all means go for it!
*** So, maybe not 50 times. Try like 47 and eyeball it from there.
**** Except not “literally,” “exact”, or “same”