So, last week, I mentioned the number of earthquakes in the world each year. Did you know that the moon has quakes too? Not surprisingly, they are called "moonquakes."
Buzz Aldrin planted a seismometer in the Sea of Tranquility while he was there. (Hmmm, that explains one of the little black boxes. My roommate from college always wondered about those, but I digress.)
According to NASA, there are at least four different kinds of moonquakes: (1) deep moonquakes, which are about 700 km below the surface, apparently caused by tides; (2) those that register vibrations from the impact of meteorites; (3) thermal quakes, believed to be caused by the expansion of the frigid crust when the morning sun first hits a spot after two weeks of deep-freeze lunar night; and (4) shallow moonquakes occurring only 20 or 30 kilometers below the surface.
Their equipment has even registered a 5.5 magnitude quake, which is strong enough to move heavy furniture and crack plaster on earth, according to NASA. Some scientists would like to deploy a series of seismometers around the moon to conduct a better study of moonquakes. That would give NASA a better idea of which parts of the moon are more stable so that they'd know where the best possible lunar base locations could be.
Too bad scientists didn't have a chance to do that before all those people moved to California.