This week, a small crack unzipped under the Santa Monica Mountains north of Los Angeles, waking millions of people with a magnitude 4.4 earthquake. (LiveScience)

Feel the Earth move under your feet? Watch “Earthquakes 101” to understand why.

The USGS makes som pretty maps, don’t they? The St. Patrick’s Day “Shamrock Shake” jolted the Southern California coast just north of Encino, colored green on this lovely map. The red lines are, of course, California’s jigsaw of (geologic) faults. The famous San Andreas fault is the long diagonal just south of Lancaster.
Map by USGS

Discussion Ideas

• Read through the short, great LiveScience article, then take a quick look at the overview of earthquakes in our “Forces of Nature” interactive. (Earthquakes are the final “force of nature”, with the seismograph icon in the upper left.) Click on slide four. It lists the four major types of faults: normal, reverse…