The Moon has earthquakes too. They are called moonquakes. Apollo astronauts left machines on the Moon to measure shaking. From 1969 to 1977, these machines recorded thousands of moonquakes. Some shallow moonquakes were quite strong and shook for more than ten minutes.

Scientists think the Moon is slowly getting smaller as it cools. When it shrinks, the ground can crack and move.

Earthquakes do not happen only on Earth. Apollo astronauts placed seismometers on the Moon, and from 1969 to 1977 these instruments recorded thousands of moonquakes. Most were deep and weak, but some shallow ones reached about magnitude 5. Strangely, shallow moonquakes can keep shaking for more than ten minutes. This is because the Moon's rocks are very dry and full of cracks, so the vibrations bounce around instead of fading quickly.

Scientists believe some shallow moonquakes happen because the Moon is shrinking as its interior cools. Like a grape turning into a raisin, its surface forms wrinkles, which appear as cliffs along faults. This matters for future bases, because young faults have been found near the Moon's south pole.

The Moon may look geologically dead, but seismometers left by Apollo astronauts tell a different story. Between 1969 and 1977, instruments from four missions recorded thousands of moonquakes. Some were deep quakes linked to Earth's tidal pull. Others came from extreme temperature swings or meteorite impacts. The most powerful were shallow quakes, reaching up to about magnitude 5.5.

Shallow moonquakes also last unusually long, sometimes more than ten minutes, because the dry, heavily fractured lunar crust absorbs little energy and scatters the vibrations again and again. Their likely cause is global contraction. As the Moon's interior cools, the crust is squeezed and breaks along faults, forming cliff-like scarps. In 2019, a Smithsonian-led team reanalyzed the Apollo data and found that several shallow quakes occurred near young fault scarps, so some of those faults may still be active.

With only four stations, however, quake locations carry large errors, and the link is statistical rather than certain. This is more than an academic question. Young faults have been identified near the lunar south pole, where Artemis landings are planned, and mission planners now have to consider the risk of quakes and landslides there.