Earthquakes

I had another article written for today, but I thought that with yesterday's earthquakes, understanding earthquakes would be a better idea. Oh, and if you think earthquakes NEVER happen in your area, follow the link at the bottom of the article.

Yesterday, April 4, 2010 a large earthquake occurred in Mexico and was felt in a large area, including L.A.

The Earth’s crust isn’t a solid piece of rock. It’s broken up into pieces of different sizes called tectonic plates. These plates float on magma that’s about the consistency of corn syrup. As the pieces float, they bump and jostle and slide past each other. But they don’t do it smoothly. The edges of these huge stone plates are rough and jagged, and they catch on each other. Movement grinds to a halt, and the pressure builds. Eventually the strain becomes too much, and the rock gives away. The plate jumps forward and releases all of the pressure at once. Just like a rubber band that breaks when it’s stretched too far, the rock stretches and breaks and whips around.

The energy and the motion ripple out from the center in three types of seismic waves. The Primary waves travel the fastest. They move the ground back and forth. Then the Secondary waves move things side to side. Finally the Surface waves move like water waves, both up & down and back & forth at the same time. Because they move in two directions at once, surface waves can cause the most damage.

Earthquakes happen all the time, but most of them are too small to feel. Here’s a map of all of the earthquakes on Earth in the last 7 days.
Earthquake data by country