This past August saw a fairly significant earthquake strike northern California, resulting in hundreds of millions of dollars in damage and multiple injuries, not to mention the loss of who knows how many bottles of fine wine. If you’re looking to explain to your kids or students how earthquakes happen, this tasty experiment is for you!
Putting the Crack in Graham Cracker
All you really need for this demonstration is a few graham crackers, but you might as well be cool about it and add some marshmallows and chocolate bars to that list. The last two aren’t necessary for the experiment, but if you’re fiddling with graham crackers, you might as well make s’mores, amirite?
Start by breaking a graham cracker in half along its perforations and realigning the two halves at the break point. With the split line pointing toward you (as opposed to sideways), slide the two graham cracker halves against each other, with one moving toward you and the other away. The two halves scraping together will create crumbs and break off a few small chunks, but the pieces should remain essentially intact.
Then, break another graham cracker apart, but not at the perforations. Snap it in twain randomly, doing your best to create a jagged split. (The good thing about his demonstration is, if you don’t get this part quite right on the first try, you can just eat your supplies and try again.) When you’ve created a good, irregular split, repeat the same process above: realign the pieces at their split point and slide their edges against each other.
You’ll notice that this time, the cracker pieces don’t move so smooth. It’ll take a bit more force, and will cause considerably more breakage and much larger crumbs.
The Delicious Science
The break line between the graham cracker pieces represents a transform fault line, which is where real earthquakes occur. The crackers themselves represent tectonic plates. In moving them past each other, you’ve replicated the mechanics of an earthquake—tension between the plates causes the mighty vibrations.
A rougher fault (or a rougher break between graham crackers) requires more pressure for the plates to move past each other. This additional pressure causes the plates to smash against each other harder, resulting in larger earthquakes and larger debris, just like the second round of cracker sliding.
Now, take the rest of your graham crackers and your previously unnecessary marshmallows and chocolate and cook up some s’mores. You can’t put those three things in front of kids and not make s’mores!