Earthquake!



Not living in an earthquake area (on a fault line), I had never experienced an earthquake, so when our floor and walls began to move in a rippling fashion, I was stunned. Steven, being from California, immediately recognized it as an earthquake. I couldn't believe it! I told him, "No, we don't have earthquakes," meaning, of course that it must be something else causing the movement but that he was thinking was an earthquake because he was used to having them from time to time as a child. Since we live across the bay from a proving ground, and we do feel shocks from it and hear them. I, at first, assumed it had something to do with that. Turns out it was indeed an earthquake registering 5.9 and centered in Richmond, Va., about 200 miles away.





We have studied plate tectonics before when we floated graham crackers on molasses to represent the earth's plates resting on the plastic rock of the upper mantle. We also rubbed graham crackers together to represent the earth's plates pushing against each other.
With the boys experiencing an earthquake this week, though, I thought we would review again some of the concepts of how and why earthquakes happen.

My youngest was not in the mood for the lesson, however, and grumbled about why we had to study earthquakes. I am sure you have experienced the grumbling with your students from time to time, too. Rather than answer the question, however, I just went on with the lesson, and picked up an egg I had hard-boiled earlier in the day with this lesson in mind. I dramatically cracked it on the table, while I said, "this is the earth."  This got everyone's attention.

source

I then talked about how the cracks represent the plates and while I moved a piece of shell around with my thumb, I talked about how these plates sometimes move about and sometimes they get hung up on each other. As one plate moves, it gets caught on the rough, jagged fault and the stationary rocks then resist the motion, eventually even bending the rock a little. At some point the moving rock breaks free of the jagged fault edges which results in the vibrations of an earthquake. For the older students, you can tell them that this is called the "Elastic Rebound Theory." If you have little ones and they don't understand how the effects could be felt so far away, you can fill a metal baking pan full of water and have them them tap the side with a fork or the like and let them see how the effects of their energy ripple through the water. It helps them to visualize the rolling effect that can felt during an earthquake.

Now, this was fun and so they then wanted earths of their own to move the plates on. I, of course, had planned on this and had plenty of eggs for them to experiment with and eat as a snack afterwards.

They then wanted to know why we had an earthquake when we don't live on a fault line. I explained to them that there are many small faults located within a plate, not just on the major fault lines, just as the eggs not only had major cracks and but lots of smaller cracks as well.

We also talked about the Richter scale, which runs from 1-10.  Each step, however is an increase of 32 times the energy of the previous step. This means that an earthquake measuring 2 on the Richter scale releases 32 times more energy than one that measures 1. Level three then is 32 x 32 times more energy, or 1,024 times more energy than a level 1 earthquake. A little hard for the little ones to understand perhaps, but interesting for the older ones.

source: Exploring Creation with Physical Science, Jay Wile