Mid-Week Mini: The Moon Has Moonquakes

In this week’s Mid-Week Mini Episode, we talk about moonquakes.

A lot of people don’t know this, but the moon has earthquakes. Or, I guess, moonquakes.

When Apollo astronauts were up there in the late 60s and early 70s, they left behind seismometers to measure activity on the lunar surface. And sure enough, those instruments started detecting tremors. Scientists were shocked to find out that the moon shakes — not constantly, but often enough to prove it’s not just some cold, dead rock floating in space.

There are actually four types of moonquakes. Some are deep, happening hundreds of miles below the surface. Others are thermal quakes, caused when the moon’s crust expands and contracts as it goes from freezing cold at night to boiling hot in the daytime. Then there are shallow moonquakes, which can be the strongest — sometimes reaching up to a 5 on the Richter scale, powerful enough to move furniture if it happened on Earth. And finally, there are moonquakes caused by meteor impacts. Because the moon has almost no atmosphere, meteors don’t burn up like they do here. They just smack into the surface, and those hits ring through the moon’s crust like a bell.

That’s the weirdest part — the moon doesn’t quake like Earth does. On Earth, an earthquake lasts a few seconds or maybe a minute. But on the moon, quakes can last for up to an hour because the moon is dry, rigid, and doesn’t absorb energy the way our planet does. Some Apollo astronauts said the entire surface seemed to vibrate.

And this is more than just trivia. If humans are going to build bases on the moon, we have to know how these quakes might affect structures. A lunar house designed for tourists in 2080 is going to have to withstand a shaky, ringing moon.

So yes — not only does the moon cause tides here on Earth, but up there, it’s got its own tremors. The internet says it’s true.