Earthquake Damage in a Small Town

About this drawing

An earthquake ground crack is one of the clearest signs that the planet has shifted beneath a town. Earth's outer shell is broken into giant slabs of rock called tectonic plates, and they are always creeping along, usually only a few inches a year, about as fast as your fingernails grow.

Where two plates grind past each other or push together, stress builds up in the rock for years or even centuries. When the rock finally snaps, it releases energy as seismic waves that race through the ground and make the surface shake. Scientists call the spot underground where the break starts the focus, and the point on the surface right above it the epicenter.

Some places shake far more often than others. Japan, Chile, California and Alaska all sit along the edges of big plates, many of them around the Pacific Ocean in a zone nicknamed the Ring of Fire. Seismologists track every tremor with instruments called seismometers, and most quakes are so small that people never feel them.

Talking about earthquakes gives kids a way to make sense of scary headlines. It also opens a conversation about how engineers design buildings that can sway without falling and why families keep an emergency plan.

• earthquake
• natural disasters
• earth science
• tectonic plates
• geology