Scientists On Edge After Confirming the Impossible Earthquake

[00:00:00]The earthquake that happened this morning and I think it happened about 10 minutes before 8:00. Maybe the most important thing to say is that it was a moderate-size earthquake.

[00:00:21]>> Imagine this.

[00:00:23]It's early morning, February 24th, 1979.

[00:00:28]Most people in the tiny town of Randolph, Utah are still asleep. No alarm goes off. Nobody feels anything.

[00:00:36]Nobody hears a thing.

[00:00:38]And yet, at that exact moment, the earth shakes. Deep, incredibly deep. A seismograph at the University of Utah captures it. A magnitude 3.8 earthquake.

[00:00:51]Strong enough that people should have felt it.

[00:00:54]But nobody does.

[00:00:56]How is that possible?

[00:00:58]A young researcher leans over the data.

[00:01:01]And what he sees is so absurd, so impossible according to everything science knew [music] at the time, that he can barely believe it himself.

[00:01:10]The earthquake didn't occur in the crust, like they normally do.

[00:01:14]It occurred at a depth of 90 km deep inside Earth's mantle.

[00:01:20]A place where earthquakes simply should not exist.

[00:01:24]For almost 50 years, this finding was brushed aside, ignored, too crazy to take seriously. Until now.

[00:01:32]Because in 2026, scientists at the University of Utah have definitively confirmed that earthquake was real. And it wasn't alone. Welcome. This is the story of the earthquake that shouldn't exist and what its discovery means for everything we thought we knew about the ground beneath our feet.

[00:01:54]Part one.

[00:01:57]What is an earthquake, anyway?

[00:02:01]Before we go further, let's do a quick refresher. Because to understand why this earthquake is so shocking, you need to know how earthquakes normally work.

[00:02:11]Earth is built like an onion. On the outside, you have the crust, the thin layer we live on.

[00:02:18]Continental crust averages about 30 to 50 km thick. Oceanic crust is thinner, around 5 to 10 km.

[00:02:27]Below that is the mantle, a massive layer of rock stretching from the base of the crust all the way down to about 2,900 km.

[00:02:36]And then, there's the core. But, we'll leave that for another day.

[00:02:40]Now, earthquakes normally start in the crust. They begin at a fault line, [music] a place where two pieces of rock slide past each other, collide, or pull apart.

[00:02:51]Enormous pressure and friction build up stress over time.

[00:02:56]At some point, the rock snaps. That snap is what we feel as an earthquake.

[00:03:02]This works because crustal rock is brittle. It can store stress and then suddenly release it.

[00:03:09]But, in the mantle, the temperature there is so extreme, hundreds to thousands of degrees Celsius, that rock doesn't break. It flows.

[00:03:19]Incredibly slowly, over millions of years, but it flows.

[00:03:24]Like honey you warm up, it becomes liquid. And a flowing substance cannot cause an earthquake. That's not an opinion. That's physics.

[00:03:34]Or so we thought.

[00:03:37]Because that logic has one enormous problem. The 1979 earthquake in Utah.

[00:03:44]Part two.

[00:03:48]The discovery nobody believed.

[00:03:52]Back to February 1979, [music] George Sand is a young post-doctoral researcher at the University of Utah.

[00:03:59]He works at the university's seismograph stations, and his job is to analyze earthquake data.

[00:04:06]On February 24th, the station detects an earthquake beneath Randolph, a tiny town in northeastern Utah, near the borders of Idaho and Wyoming.

[00:04:16]Magnitude 3.8.

[00:04:18]Nothing unusual, you'd think. At that strength, people should feel it.

[00:04:23]But two things immediately catch Sand's attention.

[00:04:27]One, nobody felt the quake. Not a single report from locals, zero. Two, the seismic waves look strange. They have a pattern that doesn't match a normal crustal earthquake.

[00:04:41]So, Sand starts calculating. He analyzes the wave patterns, compares them to other earthquakes, and works out the depth from which the quake must have originated.

[00:04:51]And the answer he gets, 90 km deep.

[00:04:55]He recalculates. Same answer.

[00:04:58]That's deeper than the bottom of the Earth's crust.

[00:05:01]That is, quite literally, inside the mantle.

[00:05:06]"The deep depth explained why it wasn't felt by people at the surface," Sand later said. "But it was hard to convince others of the highly anomalous mantle earthquake occurring in a region where none should exist."

[00:05:19]He wrote a short note about his finding, an abstract for the journal Earthquake Notes, but it went largely unnoticed.

[00:05:27]Too controversial. Too unbelievable.

[00:05:31]And just like that, [music] George Sand's discovery was buried in the archives for nearly half a century.

[00:05:38]Part three.

[00:05:41]A new generation picks up the trail.

[00:05:45]Fast forward to the present. A new generation of seismologists at the same University of Utah starts re-examining archived data. They now have better tools, [music] more powerful computers, and far more sophisticated analysis methods.

[00:06:00]Professor Keith Koper, a geology professor at the university, leads the team. They take the waveforms from the 1979 earthquake and put them through fresh analysis. But they also look at eight other suspected deep earthquakes that had been recorded since then in northern Utah and southwestern Wyoming.

[00:06:20]And slowly, the picture begins to come into focus.

[00:06:23]One by one, they confirm it.

[00:06:26]All nine earthquakes did not originate in the crust. They all happened well below the Moho, the official boundary between the crust and the mantle, named after Croatian geophysicist Andrija Mohorovičić, who first identified it in 1909. In this part of Utah, the Moho sits at around 45 to 50 km [music] depth.

[00:06:49]These earthquakes happened 5 to 60 km below that boundary.

[00:06:54]The scientists published their findings in 2025 in the journal Geophysical Research Letters.

[00:07:01]But the story wasn't finished because on September 10th, 2025, the earth moved again. Part [music] four.

[00:07:11]The 2025 earthquake, the proof comes alive. September 10th, 2025.

[00:07:17]6:00 in the evening. Near the town of Maeser in Utah's Uinta Basin, the ground shakes.

[00:07:25]Magnitude 4.1. [music] Again, almost nobody feels it.

[00:07:31]But the seismographs capture everything.

[00:07:34]And when Professor Koper's team analyzes the data, they find something extraordinary.

[00:07:40]This earthquake originated at 68 km depth, more than 20 km below the Moho.

[00:07:47]This was no longer a historical archive artifact. This was real-time confirmation that something fundamental is happening beneath Utah and Wyoming.

[00:07:58]Something we are only just beginning to understand. The team published this new case in April 2026 in the Seismological Record under the title The 10th of September 2025 magnitude 4.1 earthquake in northeastern Utah.

[00:08:16]An archetypal continental mantle event.

[00:08:20]In other words, a textbook example of a continental mantle earthquake.

[00:08:25]Science now had a name for the phenomenon, CMEs.

[00:08:30]Continental mantle earthquakes.

[00:08:33]And with that, [music] George Zandt's 1979 discovery was finally, after nearly 50 years, officially recognized.

[00:08:42]Part five.

[00:08:46]Why here? The role of the Wyoming Craton.

[00:08:50]Now the big question.

[00:08:51]Why is this happening here?

[00:08:53]Why Utah and Wyoming and not everywhere else?

[00:08:57]The answer lies in a geological structure most people have never heard of, the Wyoming Craton.

[00:09:05]A craton is an ancient, stable piece of continental lithosphere.

[00:09:10]It's literally the skeleton of a continent, billions of years old rock that barely changes.

[00:09:16]The Wyoming Craton is one such structure, and it extends beneath a large portion of Wyoming and neighboring states.

[00:09:24]But here's the fascinating part.

[00:09:27]The western edge of the Wyoming Craton borders the tectonically active western United States, a zone full of volcanoes, fault lines, and shifting tectonic plates.

[00:09:39]That's an unusual combination.

[00:09:41]An ancient, stable chunk of earth sitting right [music] next to an enormously dynamic zone. Professor Kopriva explains it with a brilliant metaphor. Think of an iceberg in a river.

[00:09:53]On the scale of millions of years, the mantle [music] is hitting the craton and then flowing around it.

[00:09:59]It's that interaction where mantle flow is being diverted around this hard cratonic root that's causing the increased strain rate, the increased deformation, and it's also creating extra stresses.

[00:10:12]We think it's that interaction between the keel of the iceberg and the medium around it [music] that's leading to these earthquakes.

[00:10:20]In other words, the Wyoming craton is like a boulder in the middle of a river.

[00:10:25]The water flows into it, around [music] it, and through that turbulence, eddies and forces are created that wouldn't normally exist.

[00:10:33]In the earth, that turbulence isn't water, but slowly flowing rock. [music] And the forces it generates are apparently powerful enough to, against all expectations, cause that rock to break.

[00:10:47]There's also another mechanism researchers [music] are investigating.

[00:10:51]Thermal runaway. When rock is compressed under extreme pressure and heat, the friction can generate so much local warmth that the rock becomes even more fluid, which accelerates deformation, which generates more heat until a fracture forms.

[00:11:07]This is a different kind of breaking than [music] in the crust, but the result, an earthquake, is the same. Part six.

[00:11:17]What does this mean for science?

[00:11:21]Okay, but why is this such a big deal?

[00:11:23]Aren't these just a handful of small earthquakes in a remote corner of America? Well, the implications reach far beyond Utah and Wyoming. First, we need to rewrite the textbooks. The definition of where earthquakes can occur has always been based on the assumption that mantle movements are too slow and [music] too hot to cause brittle fractures.

[00:11:45]CMEs prove this isn't always true. There are conditions, specific geological structures, specific temperatures and [music] pressures under which mantle rock can still behave like a brittle material. That opens an entirely new field within seismology. Second, there are probably far more of these earthquakes [music] than we realize.

[00:12:05]Because nobody took CMEs seriously, they were simply dismissed as measurement [music] errors or data anomalies in the past. Now that scientists know what to look for, old archives are being re-examined.

[00:12:18]A global catalog has already been published listing 459 confirmed continental mantle earthquakes since 1990 worldwide, not [music] just in America.

[00:12:30]This phenomenon is not unique to Utah.

[00:12:32]It also occurs near the Himalayas and Tibet and in other places where ancient cratons border active tectonic zones.

[00:12:40]Third, seismic hazard. This is the most practical question. Are these deep earthquakes dangerous? For now, the CMEs in Utah appear to have relatively small magnitudes between 3.8 and 4.1.

[00:12:56]They aren't felt at the surface because of the enormous depth, but the discovery raises real questions. Can deeper mantle earthquakes reach larger magnitudes? And if they do, what are the consequences at the surface? [music] Scientists don't know yet, but that's exactly why this research matters so much.

[00:13:16]Fourth, the nature of seismic silence.

[00:13:20]One of the most fascinating characteristics of CMEs [music] is that they occur in isolation.

[00:13:26]They almost never have foreshocks or aftershocks. They shoot up from deep in the earth like lone wolves, and then it goes quiet again.

[00:13:36]That makes them exceptionally difficult to study.

[00:13:39]Normally, you use the aftershocks of an earthquake to map the fault zone.

[00:13:44]With CMEs, you don't have that. It's like a ghost briefly passing through a wall and then [music] vanishing without a trace. Part seven.

[00:13:55]The man who was right all along.

[00:13:59]I want to take a moment to honor the man who started all of this.

[00:14:03]George Zandt.

[00:14:05]In 1979, he had the courage to say something that no colleague wanted to hear.

[00:14:11]He published his finding, watched it get ignored, and moved on with his career.

[00:14:16]Eventually becoming a professor of geology at the University of Arizona.

[00:14:20][music] But the data stayed. And the questions stayed.

[00:14:25]Nearly 50 years later, the world has finally caught up.

[00:14:29]"I did some other analysis that convinced me of the reality of the deep depth," Zandt said in a recent statement. "But it was hard to convince others of the highly anomalous mantle earthquake occurring in a region where none should exist."

[00:14:44]That's a story that repeats itself throughout the history of science.

[00:14:48]An extraordinary discovery that arrives years, sometimes decades too early for the rest of the world to [music] accept it.

[00:14:56]Sometimes the discoverer is right.

[00:14:59]Sometimes they're not.

[00:15:01]But one thing always holds.

[00:15:03]Good data doesn't disappear.

[00:15:06]It waits.

[00:15:07]In George Zandt's case, it waited nearly 50 years. Part eight.

[00:15:15]What comes next?

[00:15:19]So, what now? Professor Kopers' team continues to monitor the region. They now know that more CME's will likely follow. It's only a matter of time. With detection equipment far more advanced than what [music] existed in 1979, these earthquakes can now be recorded and analyzed in real time. There are also plans to expand the seismic network across the Wyoming Craton area. More seismometers, more data, better maps of [music] what is happening deep beneath the surface. Internationally, scientists are now re-examining earthquakes [music] that were previously dismissed as anomalies. There may be more hidden CME's waiting to be discovered in archives [music] all around the world.

[00:16:03]And the big question remains, is this phenomenon rare, or does it happen far more often than we ever imagined?

[00:16:12]Earth has always guarded her secrets [music] carefully. But with every new discovery like this one, we gain a little more insight into the enormous machine running beneath us. Day and night, invisible and silent, until suddenly a seismograph needle spikes.

[00:16:31]The earthquake of February 24th, 1979 beneath Randolph, Utah registered a magnitude of 3.8.

[00:16:40]Nobody felt it. Nobody heard it.

[00:16:43]But somewhere in an archive cabinet at the University of Utah, it slept all those years. Patiently waiting for the day science would finally take it seriously.

[00:16:55]That day has come. And what we now know fundamentally changes how we look [music] at the Earth. Not just at what happens on the surface, but at what is truly taking place deep, deep below in the flowing interior of our planet.

[00:17:13]The Earth is far from finished speaking.

[00:17:16]If you found this video fascinating, hit that like button and subscribe to the channel. [music] We regularly dive into the latest geological, astronomical, and scientific discoveries that will change the way you see the world. Until next time, take care of yourself and of the ground [music] beneath your feet.