00:007,500 years ago, the Pacific floor collapsed.
00:04Massive landslides buried the seabed in seconds.
00:08Fast forward to today, robot subs have examined the place.
00:11Scans have revealed proof of at least 10 distinct cyclical megaquakes.
00:16Now, researchers warn, the plates are still locked and building pressure, even today.
00:22If they start moving, that could trigger new red alert earthquakes and send disastrous tsunamis toward the coast.
00:30Let's look at the map.
00:32The fault here is like a giant zipper.
00:34It's over 600 miles, stretching from northern California to Canada.
00:39It's called the Cascadia Subduction Zone, and it's a part of the Ring of Fire.
00:44You know, the famous giant horseshoe around the Pacific that can serve as your where-to-go reminder if you're
00:50into volcanic and earthquake tourism.
00:53One of Cascadia's biggest events happened around the year 1700.
00:57There are no local written records of it, but there is a story.
01:02A well-known indigenous legend tells of an epic battle between a thunderbird and a whale.
01:08In the story, the thunderbird's wingbeats make the ground shake.
01:13The whales thrashing send seawater flooding inland.
01:16The thunderbird wins by finally grabbing the whale and slamming it back down, shaking the land itself.
01:24Many researchers believe that this legend originated from the real earthquake of 1700.
01:31But we don't just have cool myths to give us the full picture.
01:34In the early 1700s, samurai officials recorded waves flooding villages and rice fields.
01:40But nobody felt the earthquake that must come first.
01:43That's why they nicknamed this event the Orphan Tsunami.
01:47But it did have a parent.
01:49And it took scientists 300 years to finally connect it back to Cascadia.
01:56To see Cascadia's past, researchers sent robot subs to scan the bottom in crazy detail.
02:03They expected to see a simple crack, but what they found looked more like giant underwater steps.
02:10Some of those steps are about 33 feet tall, like a three-story building.
02:16That only happens when a big piece of the seafloor snaps off, breaks loose, and slides all at once, not
02:23slowly.
02:23When that happens, it kicks up a mud avalanche.
02:28Picture a jar of dirt and water.
02:30Shake it hard.
02:31And a fresh layer settles at the bottom.
02:34Each layer is basically a timestamp from a huge quake.
02:38When scientists counted and dated them, they found 10 separate megaquakes that hit one after the other over thousands of
02:46years.
02:47That means that Cascadia doesn't let pressure out little by little.
02:52It stays stuck for a long time, then suddenly breaks out violently.
02:57That pattern is why the Cascadia subduction zone is considered one of the scariest fault systems in North America today.
03:06So what's actually happening down there?
03:08The plates aren't sliding smoothly.
03:11They're stuck.
03:11And while they're stuck, the coastline is getting quietly bent out of shape, like a ruler you're flexing in your
03:17hands.
03:18It doesn't look dramatic day to day, but it's been loading up for centuries.
03:23When that tension finally snaps, the coast will instantly drop.
03:29Geologists call this co-seismic subsidence.
03:32We're talking about the ground plunging 6 to 8 feet vertically in a matter of minutes.
03:37Imagine standing on a beach.
03:39The shaking stops, and you realize the ocean is rushing in.
03:44Not just because of a wave, but because the land you're standing on has physically sunk below sea level.
03:51That one move is enough to shove the seafloor out of position and force the ocean above it to react.
03:59Cascadia can produce a magnitude 9.0.
04:03That's top tier, categorized as the most destructive natural event that can happen.
04:08It can shake the ground for minutes, pushing and pulling everything back and forth until buildings and bridges start falling
04:16down.
04:17A 9.0 class quake also means the seafloor is vibrating and shifting, lifting in some spots, dropping in others,
04:25all in one sudden motion.
04:28A tsunami starts when the seafloor moves and pushes a huge amount of water out of the way.
04:34If the bottom suddenly lifts or drops, the water above it gets displaced instantly.
04:39That water has to go somewhere, so it races outward in every direction.
04:46Out in deep water, that wave is rarely tall.
04:49It spreads out across a long distance, so it can pass under ships without anyone noticing.
04:55The danger is speed.
04:57In the open ocean, tsunamis can travel around 500 to 600 miles per hour.
05:04That's like traveling from New York to Detroit in 60 minutes.
05:08Eventually, the ocean starts to pile up, getting taller by the second.
05:13Near shore, it can stack up to tens of feet, and in extreme cases, it can run up to 100
05:19feet on land.
05:21It swallows the coast, then drags everything back to sea with a violent tug before the next hit arrives.
05:29But that's not all.
05:30When the fault snaps, it often triggers massive underwater landslides.
05:34When a huge chunk of seafloor collapses, it can shove water locally, like dropping a boulder into a tub.
05:41In the Cascadia subduction zone, you aren't just dealing with the earthquake's kick.
05:46You're getting a one-two punch from the shifting crust and the crumbling slopes combined.
05:52On parts of the Oregon coast, emergency experts say the shaking could last 5 to 7 minutes, long enough to
05:59realize what's happening and still won't be over.
06:03Then comes the scariest part.
06:05In some places, a tsunami can hit in 15 to 30 minutes.
06:11Remember, the earthquake is a warning.
06:14If you're on the coast and you feel strong, long-shaking, you do not need to wait for a text
06:19alert or a siren, or someone on the news to yell, Tsunami!
06:23During the tremors, the basic recommendation is to literally drop to the ground, cover, and hold on, staying away from
06:30windows and chandeliers that can fall on you.
06:33As tempting as it is, we shouldn't stop to make a reel out of the situation.
06:39Before anything happens, make one decision while your brain is calm.
06:43Pick the closest high ground and go for it.
06:46Not somewhere uphill, an actual spot.
06:49If you ever needed a reason to learn your neighborhood, this is it.
06:53Your instinct might say, get into the car and drive.
06:57But don't.
06:58Roads are probably jammed and bridges could be damaged.
07:01People who live on the coast already know to keep it practical, with shoes on the bed and a go
07:06-bag prepared just in case.
07:08The danger doesn't end with the first impact because a tsunami waves, well, they come in waves.
07:15The initial hit is rarely the largest, and the ocean can continue to pulse in and out for hours.
07:22This creates a violent tug-of-war.
07:24The receding water acts like a massive vacuum, dragging anything caught in the backwash out to sea.
07:31Japan's 2011 disaster is the most recent vivid example of what a magnitude 9.1 can do.
07:38The seafloor shifted in a single massive heave, and minutes later, the ocean literally rearranged the coast.
07:46A huge wall of water crashed inland, reaching over 100 feet high in some spots, and turning the coastline into
07:55a conveyor belt of debris.
07:57It was like water turned cars into giant bowling balls and shipping containers into massive metal bricks, smashing ports and
08:05drowning low-lying airports and electrical substations.
08:09Finally, what do officials say about the timeline for the possible next disaster hitting Cascadia?
08:16Well, they can't give us precise dates, but they did announce some odds.
08:21For the biggest, scariest earthquake possible, the United States Geological Survey says there is about a 10% to 15
08:29% chance it'll happen in the next 50 years.
08:33Chances for a quake that isn't the mega version are 1 in 3 in the next 5 decades.
08:39Those odds are actually pretty high.
08:41But here is why it isn't all that grim.
08:45Scientists know this isn't random.
08:47Cascadia has a pattern, and patterns are what preparation runs on.
08:52We already know how to build for big shaking, and we're getting better at spotting where stress is building.
08:59It doesn't mean we can stop the earthquake, but it means we're getting way better at knowing what to expect.
09:05In the meantime, just keep a go-bag by the door and maybe take a walk around your neighborhood every
09:11once in a while.
09:13That's it for today.
09:14So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
09:19Or if you want more, just click on these videos and stay on the bright side!
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