Earthquakes on the Computer

So why does the earth crackle?

We know some things. We know that Earth's crust moves, and that earthquakes happen at the places where different parts of the Earth's crust rub against one another. Each big piece of the Earth's crust is called a tectonic plate; the places where two plates rub and slide are fault lines. Normally, the two plates are stuck together at the fault line, and the plates get bent more and more as they slide in different directions. Every once in a while, the plates slip at the fault line, and this makes an earthquake!

Some scientist friends of ours came up with a simple version of a fault. If you see a bunch of green blocks sliding on a marble table, their theory is running on your computer! One of the tectonic plates is the marble table: it's sliding to the right. The other one is made of the green blocks, which are held together by springs and kept from moving by being connected to the black bar on top. You can see the green blocks sticking (sliding with the table) and getting unstuck (an earthquake!)