The pull of the moon is so strong that it can trigger earthquakes on Earth.  Scientists are still baffled by its potency.
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  • The Moon’s gravity is constantly pulling on the Earth.
  • Its appeal to the oceans is undeniable, but some scientists are studying less visible effects.
  • They discovered that the moon could trigger earthquakes, if the time was right.

Our moon has an undeniable effect on the Earth’s tides. Its gravitational pull causes our planet’s sea level to rise and fall.

But what if the moon were to have a smaller, less visible effect on our planet?

A small handful of experts claim to have proof that our satellite produces forces that can trigger earthquakes.

The effect of the moon on earthquakes was hidden

Scientists have long wondered if the moon’s tides could be linked to earthquakes. After all, our satellite is still there, shifting the weight of the oceans and tugging at our planet.

A gif showing the earth and the static moon shows how the tides lift the oceans towards our moon.

An animation illustrates how the moon’s gravity creates tides on Earth.

NASA/Vi Nguyen



Certainly, all this pressure, even if gradual, would have a significant effect, the scientists asked.

But until recently, the datasets weren’t good enough to show the link between the moon and earthquakes, and the pull was deemed too weak to have a significant impact.

“For a while it was a field where only fools worked,” Chris Scholtz, a geologist and professor emeritus of earth and environmental sciences at Columbia Climate School, told Insider.

But with the advent of larger and more comprehensive datasets over the past 20 years, the influence of the moon has begun to emerge from the data. And it seems that in some cases the moon has helped trigger earthquakes around the world.

“With these huge datasets, they started to get a small but significant correlation,” Scholtz said, adding, “Now it’s believable,” he said.

The moon can put the weight of the ocean on a volcano

Images taken by a satellite show the Moon passing through the Earth.

The images show the moon rotating around the Earth. Scientists are beginning to uncover the moon’s tiny but powerful effect on Earth’s earthquakes.

NASA/NOAA



One place where the impact of the moon is clearly visible is in submarine earthquakes. That makes sense, given the moon’s pull on the oceans.

A 2004 paper published in the peer-reviewed journal Science, for example, found that earthquakes along submarine fault lines appeared to follow ocean tides.

Scholtz and his team set out to study how the moon might exert its power on earthquakes from Axial Volcano on the Juan de Fuca Ridge off the west coast of the United States. Earthquakes here are about ten times more likely to occur when the tide has receded, Scholtz said.

A graph shows that earthquakes are much more frequent when the tide is around its 0 phase, i.e. when the tide is low.

A graph shows the number of earthquakes occurring as a function of tidal phase. Phase 0 means the tide is receding.

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Scholz, CH, Tan, YJ & Albino, F. Nat Commun 10, 2526 (2019). DC BY 4.0



Their study, published in Nature Communications in 2019, found an explanation for the link between the moon and earthquakes. This suggested they were caused by the weight of the ocean pressing down on a volcano’s magma chamber.

“What happens is that the tides actually cause the magma chamber to inflate and deflate,” he said. “That’s what causes earthquakes.”

Then, when the tide is low, less water presses against the chamber, which then inflates. This, in turn, puts more pressure on the fault line, making it more likely to shake and create an earthquake.

The moon also pulls on the rocks of the Earth

an image shows the moon peeking out against the daytime sky behind a mountain ridge.

The moon also pulls like the rock of the Earth.

Getty Images



It’s not just in the oceans that the moon is wreaking havoc. Although we may not feel it, the moon also causes tiny but significant tides in the rocks.

Standing on the Earth’s surface, it can be hard to imagine mountains ebbing and flowing like the ocean, but rocks bulge and crash under the pull of the moon.

“Solid earth tides are the same as tides, it’s just on solid earth. And the amplitude of motion is very small because the earth is very rigid,” Scholtz said.

“You can measure it with a very sensitive instrument. But you can’t notice it,” he said.

These tides can distort the Earth by up to about 22 inches vertically and about 11 inches horizontally each day, Davide Zaccagnino, a doctoral student in geophysics at Sapienza University in Rome, told Insider in an email.

Digging into these datasets, a few studies have suggested a link between earth tides and earthquakes.

“While fluids can flow, rocks can slightly change shape depending on the intensity and direction of the tidal disturbance, which promotes stress buildup,” Zaccagnino said.

If the rocks are already overloaded due to the action of tectonic forces, even a small stress the pull of the moon can be the chaff that breaks the camel’s back, creating a crack in the rock, he said. .

“If the surrounding rocks are also unstable, the fracture can accelerate to involve large faults. The end result is an earthquake,” Zaccagnino said.

He can push earthquakes overboard

Let’s get one thing clear: the moon doesn’t cause these earthquakes. Rather, it’s when the rock is about to collapse that the moon’s little tug could push it past that final tipping point.

This only happens in very specific circumstances, such as when the pressure of the moon’s gravitational pull lines up perfectly with the fault line. So it’s not like we can say that every earthquake is more likely to happen when the moon is out.

“Tides cannot help us predict earthquakes. But they can help us better understand their physics, which is still largely unknown,” Zaccagnino said.

Knowing when the moon’s pull might have kicked in during an earthquake can help us, for example, understand when the crust was at a breaking point, Zaccagnino said.

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