Between 1969 and 1972, Apollo astronauts placed seismometers on the moon. Data collected from them shows that the moon experiences moonquakes, the result of steady shifting of material in the moon’s interior. In the 9170s, a 5.5-magnitude moonquake shook the lunar surface at full force for more than 10 minutes. There are four classifications of moonquakes: deep, thermal, meteoroid impact and shallow. Moonquakes are less common than earthquakes and, other than shallow moonquakes, are weaker than earthquakes.
When the tectonic plates rumble and an earthquake occurs, the huge amount of energy spreads out through the mineral-rich crust of the earth, which has largely been infiltrated by water in the stone. In effect, this makes the material slightly more compressible, and able to absorb energy and seismic waves, diminishing the power and slowing the shaking. Even so, they can still be scary – and unexpected!
On the moon, things are very different, as the entire ball is hardened, rigid and dry. When a tremor rocks the surface of the moon, it resonates powerfully, without anywhere to naturally dissipate. It isn’t uncommon for a moonquake to last for ten minutes or more, and for smaller trembling to continue for hours afterwards.
Picture Credit: Google
