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Scientists are warning about shifting forces that could have serious consequences for our planet. From Earth’s tilt to the rising risk of megathrust earthquakes, here’s what you need to know.
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00:00Doctor, I can't understand what's going on. I feel dizzy and, uh, how do I say it? I'm tilted.
00:07It didn't happen overnight. Like, I didn't wake up and couldn't stand straight.
00:12No, one day, I felt that my axis had shifted by one inch. Another day, it was two inches.
00:19And once, you won't believe it, it was 31.5 inches. That's alarming.
00:25What if I accidentally turned upside down and all my inhabitants fall off my surface?
00:30Ah, dear Earth, we ran some tests and are ready to explain an unfortunate combination of factors that has affected
00:37your axis.
00:38The last one will perhaps be the most unexpected and upsetting.
00:42It all started back in March 2011, when a devastating magnitude 9 earthquake struck off the coast of Japan.
00:50It was so powerful that not only did it shift Earth's axis, but it also shortened the length of the
00:57day.
00:58This earthquake displaced our planet's axis by approximately 6.5 inches and may have moved Japan's main island by about
01:078 feet.
01:08Like other similarly massive earthquakes, it also altered Earth's rotation speed.
01:13To make it easier, let's compare it to a spinning ice skater.
01:18When a skater pulls their arms close to their body, they spin faster by concentrating their mass near the axis
01:25of rotation.
01:25Something similar happens during the most powerful earthquakes.
01:30They shift Earth's mass closer to its rotational axis, causing it to spin faster and shortening the day length.
01:38The calculations showed that the Japanese earthquake sped up Earth's rotation by about 1.8 microseconds, which is about 1
01:46.8 millionths of a second.
01:48Not a big deal, but at the end of the day, every nanosecond counts.
01:54For comparison, the infamous Indonesian earthquake shortened the length of a day by 2.68 microseconds.
02:02It struck on December 26, 2004 at 0.58 UTC.
02:08The epicenter lay off the western coast of northern Sumatra, Indonesia.
02:13This powerful undersea earthquake triggered devastating tsunamis that swept across the Indian Ocean,
02:20causing widespread destruction and immense loss of life in countries like Indonesia, Sri Lanka, India, and Thailand.
02:29Even coastal areas as far as East Africa had severe damage.
02:33The Earth's magnitude, initially recorded at 9.0 on the Richter scale, was later adjusted to between 9.1 and
02:429.3,
02:44making it the most powerful earthquake ever recorded in Asia.
02:48The faulting, that's when Earth's crust completely breaks and its parts slide past each other,
02:54lasted between 500 and 600 seconds, and it was the longest duration ever observed.
03:01The immense force of the quake caused the entire planet to vibrate by at least half an inch
03:07and triggered other earthquakes as far away as Alaska.
03:11All that immense energy the earthquake released caused subtle but quite measurable changes to Earth.
03:18The shift in mass slightly changed the planet's rotation, shortening the day.
03:23It also caused a small wobble in Earth's axis, from 1 to 2.4 inches, toward 145 degree east longitude.
03:33So, when it comes to changes in Earth's rotation speed and axis,
03:38it's all about the redistribution of mass.
03:41This can happen naturally, through disasters, but human activities can also trigger it.
03:48Take the Three Georges Dam, for instance.
03:51This massive structure across the Yangtze River in China's Hubei Province may seem to be an engineering triumph,
03:59but it's pretty ambiguous.
04:02Finished in 2012 after nearly 20 years, this massive dam is 7,660 feet long and 607 feet high.
04:11And yes, and yes, it is so big that it can affect the way our planet spins.
04:18Its reservoir is capable of holding 9.5 cubic miles of water,
04:24has enough mass to slightly alter the Earth's rotational inertia,
04:28slightly slowing the planet's rotation.
04:32According to NASA, the Three Georges Dam reservoir could shift Earth's pole position by almost 1 inch
04:38and increase the length of a day by 0.06 microseconds.
04:44Dams aren't the only worry.
04:46If polar ice melts, water rushes into the oceans, hiking up sea levels, especially near the equator.
04:53This mass shift slows Earth's spin way more than dams do.
04:58You won't feel it day to day, but it can affect ultra-precise equipment, such as atomic clocks.
05:04To fix this, scientists suggested a negative leap second,
05:09making a minute 59 seconds to balance Earth's spin changes.
05:15Okay, so you're thinking you've got nothing to do with all those tilts.
05:19You don't build dams, right?
05:22Bad news.
05:23If you take regular showers, you're part of it too.
05:26Every time you turn on the tap, you're affecting Earth's tilt just a tiny bit.
05:31Thing is, our planet is always shifting and adapting,
05:35so even small actions like using water can influence its orientation.
05:41Over the past two decades, groundwater pumping has caused the Earth's tilt to shift by 31.5 inches.
05:49This water redistribution is equal to about 0.24 inches of sea level rise.
05:54It turns out that among climate-related causes,
05:59groundwater redistribution has the largest impact on the drift of Earth's rotational pull.
06:05But what is groundwater?
06:08It's the water stored beneath the Earth's surface,
06:11filling the spaces in soil, sand, and rock.
06:14It comes from rain and other precipitation that seeps into the ground,
06:19collecting in underground reservoirs, aquifers.
06:22Unlike rivers and lakes, groundwater stays below the surface,
06:26acting like a natural water reserve.
06:29Thanks to it, we have a steady supply even during dry periods.
06:34Many people, especially in rural areas,
06:37rely on groundwater as their main source of drinking water.
06:40Farmers use it to irrigate crops,
06:43while industries depend on it for manufacturing and cooling systems.
06:47It sounds pretty harmless, doesn't it?
06:49How can something so useful cause our planet to shift?
06:53Well, a study covering data from 1993 to 2010
06:57revealed that we've pumped about 2,150 gigatons of groundwater in that time.
07:05And this large-scale water removal has shifted the Earth's tilt and rotation.
07:10After we use groundwater, much of it eventually flows into the oceans,
07:15contributing to rising sea levels.
07:18In areas like western North America and northwestern India,
07:22people use a lot of groundwater.
07:25And it may have a connection to these shifts.
07:29Yikes! Let's face it.
07:31All these findings are rather disturbing.
07:33But, you know, understanding the impact of groundwater use
07:37is already a huge step in the right direction.
07:40Hey, I'm not done yet.
07:42This tilting issue isn't just about stuff happening on Earth.
07:46We also need to look at space.
07:49We've talked a lot about water, right?
07:52Well, you know that the Moon has a big role in that.
07:55Its gravity is super important for forming tides and all that.
07:58So, one more thing that affects our planet a lot
08:02is the gradual movement of the Moon away from Earth.
08:06These two bodies interact gravitationally,
08:09which makes Earth's rotation slow over time,
08:12even though significant events like earthquakes
08:14occasionally speed it up temporarily.
08:18How did we figure it out?
08:20Glad you asked.
08:21Once, someone paid attention to ancient corals.
08:24After analyzing them,
08:27scientists realized that Earth had once rotated much faster.
08:31The thing is,
08:33corals grow by laying down thin layers of calcium carbonate.
08:37They do it daily,
08:38and variations reflect seasonal changes.
08:41By counting these layers,
08:44scientists have calculated the number of days in a year
08:47millions of years ago.
08:49They found that Earth had about 420 days per year
08:54444 to 419 million years ago.
08:58But over time,
08:59the Moon's influence had caused Earth's rotation to slow.
09:03And now,
09:04we only have 365 days in a year.
09:07I feel robbed, you know?
09:10At the moment,
09:11the Moon is moving 1.5 inches away from Earth each year.
09:16That's about the same speed at which your fingernails grow.
09:19Astronomers have figured it out
09:21with the help of special mirrors
09:23placed on the Moon during the Apollo missions.
09:26For over 50 years,
09:28researchers have been sending laser beams to these mirrors
09:31and measuring the time it took for the light to bounce back.
09:35In any case,
09:36dear Earth,
09:37at the moment,
09:38your condition isn't critical.
09:40As for your inhabitants,
09:41they won't fall off your surface.
09:43All thanks to your gravity,
09:45pulling them toward your center.
09:47Just don't switch it off,
09:49and everything's going to be fine.
09:52There is a powerful force hiding underground
09:55where tectonic plates meet,
09:57and one forces another under it.
09:59This happens in the Pacific and Indian Oceans.
10:03Strain builds over centuries.
10:05The tension is unbearable
10:06until the megathrust awakens.
10:09The Earth shakes with a magnitude
10:11that can exceed 9 points,
10:13more powerful than any other earthquake.
10:16When the seafloor suddenly gets pushed up fast,
10:18it sends a huge ripple across the water,
10:21and a tsunami of huge force is out.
10:24These waves are called tele-tsunamis,
10:26and they cross entire ocean basins,
10:29ready to take over coastlines
10:31thousands of miles away.
10:33The thrust fall stretches over 600 miles.
10:36The Earth is not just shaking,
10:38it feels like it's tearing apart.
10:41This is the power of a megathrust earthquake.
10:44Those caught in its path
10:45will have to fight for their lives.
10:49Japanese authorities recently had to issue
10:51their first-ever megaquake advisory.
10:54It happened because of a strong tremor
10:56on the edge of the Nankai Trough ocean floor zone.
10:59In the end, most of the warnings were lifted,
11:02and there wasn't much damage
11:03from the 7.1 magnitude earthquake.
11:06Parts of southwestern Japan started to shake,
11:09and the super-fast trains in Japan
11:11slowed down to stay safe,
11:13which made travel slower for everyone.
11:15But everyone is staying alert
11:17as they know about the risk
11:18of a megathrust earthquake
11:20that could happen within the next few decades
11:22in the Nankai Trough.
11:24The tectonic plate under the Philippine Sea
11:27is slowly sliding underneath the land where Japan is,
11:30moving just a few inches every year.
11:33The last big earthquakes from this area
11:35happened in 1944 and 1946,
11:39both with a magnitude of 8.1.
11:41These quakes have caused
11:43a lot of destruction in the country.
11:45The next megathrust earthquake in the region,
11:47if it does happen,
11:49could be between a magnitude 8 and 9.
11:52Scientists still can't agree
11:53on how likely this mega-earthquake is to happen,
11:56but it could be up to 80% certainty.
12:01On the other side of the Pacific,
12:04scientists from the U.S. Geological Survey
12:06have studied a dangerous area
12:08along the U.S. west coast.
12:10It's called the Cascadia Subduction Zone,
12:13and it stretches from northern California
12:15to northern Vancouver Island in Canada.
12:18Over the past 14,200 years,
12:21there have likely been at least 30 big earthquakes
12:23in this region,
12:25when major quake happens every 500 years on average.
12:28But for a long time now,
12:30Cascadia has been quiet,
12:32and it worries scientists.
12:34They think this might be because the area is locked,
12:37meaning the tectonic plates are stuck together
12:39and building up a lot of pressure.
12:42Eventually, the part of the seafloor
12:44could suddenly break and move by several feet.
12:47The shaking would be just five minutes,
12:49but it would create a powerful tsunami
12:52as the seafloor shifts that would last for 10 hours.
12:55If it happens, it's going to be the worst natural disaster
12:58in the country's history, according to experts.
13:01The ground on some inland hills
13:03could turn into something like quicksand.
13:05This would cause the hillsides to slide and crumble,
13:09taking down roads and bridges.
13:11Around 620,000 buildings could be badly damaged
13:14or even collapse,
13:16including about 100 hospitals and 2,000 schools.
13:20People in Washington state
13:21might have to take care of themselves
13:23without help for two weeks,
13:25finding food, water, and shelter on their own.
13:30Scientists are studying slow-slip events,
13:33where the tectonic plates move very slowly
13:36over weeks or months,
13:37releasing some energy,
13:39but not enough to stop a big one.
13:41Every time the magnitude of an earthquake
13:43goes up by just one number,
13:46the energy it releases is 40 times bigger.
13:48So we'd need about a million small earthquakes
13:51every day for 500 years straight
13:54to release the same energy
13:55as one huge magnitude 9 earthquake.
13:58But these small earthquakes might be clues
14:01that a bigger earthquake is coming.
14:03To better monitor the Cascadia fault,
14:06experts are mapping the fault more accurately
14:08and adding better monitoring tools offshore.
14:11Scientists receive over $10 million
14:14to install seismic sensors
14:16and seafloor pressure gauges
14:17on a fiber-optic cable
14:19off the coast of Oregon.
14:21The goal is to be ready to warn people
14:23and potentially save lives
14:25when a big earthquake strikes.
14:30A sharp megathrust earthquake
14:32happened in this part of the world in 1964.
14:36It went down in history
14:37as the Great Alaska Earthquake
14:39and had a magnitude of 9.2.
14:42It lasted for more than four minutes,
14:44making it the most powerful earthquake
14:46in the history of the U.S. and North America.
14:49The ground shook so hard
14:51that it caused huge cracks and landslides.
14:54In Anchorage, many houses, buildings, and roads
14:57were destroyed
14:58because they weren't built
14:59to handle such a big earthquake.
15:01In some places,
15:02the land was permanently changed.
15:04For example,
15:05the coastline near Kodiak
15:07and Henschenbrook Island
15:08was lifted by 30 feet.
15:10In other areas,
15:12like Gurwood and Portage,
15:13the ground sank by 8 feet.
15:16They had to rebuild roads higher
15:17so they wouldn't be flooded by the time.
15:20A huge 27-foot tsunami
15:22wiped out the entire village of Chenega.
15:25Many coastal towns were heavily damaged,
15:27not just by the earthquake,
15:29but also by tsunamis
15:30in the fires that followed.
15:32After the main earthquake,
15:34there were thousands
15:34of smaller aftershocks for months.
15:39A moderate earthquake
15:40of magnitude 4.4
15:42shook Los Angeles in August 2024.
15:46Once it was over,
15:47the LA Fire Department
15:48checked around the city
15:49and didn't find any major damage
15:51or anyone hurt.
15:52In the nearby city of Pasadena,
15:55which is close
15:55to the earthquake's epicenter,
15:57a water pipe burst inside City Hall
15:59and everyone had to leave the building.
16:02Thankfully,
16:02there was no danger of the tsunami.
16:04The best we can do
16:06to avoid panic in such situations
16:08is to be prepared.
16:11Japan is one of the places on Earth
16:13where earthquakes happen the most
16:15because it sits on the edges
16:16of four tectonic plates.
16:18Around 1,500 of these earthquakes
16:21each year are noticeable.
16:23Because of this,
16:24the people in Japan
16:25have learned to live with earthquakes.
16:27The 1950 law set a rule
16:30that buildings should be able
16:31to handle earthquakes
16:32up to a magnitude 7
16:34without falling apart.
16:36An update 30 years later
16:38said that buildings
16:39should only have minor damage
16:40in such earthquakes
16:41and still work as usual.
16:43But if an earthquake
16:44is even stronger,
16:45the law says
16:46the building's main job
16:47is to not collapse
16:49and save people's lives.
16:51At the most basic level,
16:53buildings are made stronger
16:54with thicker beams,
16:55pillars, and walls
16:56so they can handle shaking better.
16:58Another technique
16:59is placing special pads
17:01made from materials like rubber
17:03at the base of a building.
17:04Some buildings
17:05are even built
17:06on thick layers of padding
17:07that separate them
17:08from the ground completely,
17:10which helps protect them
17:11during an earthquake.
17:12A skyscraper might sway
17:14back and forth a lot,
17:15moving up to 5 feet.
17:17To stop it
17:18from getting damaged,
17:19engineers can add
17:20something called dampers
17:22every second floor
17:23all the way to the top.
17:25These dampers
17:26are like giant bicycle pumps,
17:28but instead of air,
17:29they're filled with liquid.
17:30When the building shakes,
17:32the dampers push
17:33against the liquid
17:34inside them.
17:35Even though the liquid
17:36doesn't squish very much,
17:37it can still absorb
17:39some of the shaking.
17:42When they're building
17:43tall skyscrapers,
17:44engineers try to make
17:46the structure
17:46as simple and balanced
17:47as possible.
17:48This means having
17:50each floor the same height
17:51and placing the support
17:52columns evenly.
17:54But sometimes,
17:55architects who design
17:56skyscrapers
17:57don't want to make
17:58these compromises
17:59because they have
18:00creative ideas
18:01for how the building
18:02should look.
18:03Then, they have to find
18:04compromise solutions.
18:06For example,
18:07Tokyo's Skytree Tower,
18:09one of the tallest
18:10buildings in the world,
18:11is designed
18:12in a futuristic style
18:13but also includes
18:14special features
18:15to protect it
18:16from earthquakes.
18:17It has a central pillar,
18:19like in traditional
18:20Japanese pagodas
18:21and seismic dampers
18:22that help absorb
18:23the energy
18:24from an earthquake,
18:25keeping the building safe.
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