How Do Tsunamis Work?

Hiroshi Kawahara, AFP/Getty Images
Hiroshi Kawahara, AFP/Getty Images

Tsunamis have been wreaking havoc on the world's coastlines for centuries. Since 1850 alone, tsunamis have been responsible for taking 420,000 lives and causing billions of dollars in damage. How do these monster waves work?

DON'T CALL IT A TIDAL WAVE

Tsunamis have nothing to do with the wind-generated waves we're used to seeing, or the tides—they’re a set of ocean waves caused by the rapid displacement of water. Most commonly, this happens when large underwater earthquakes push up the seabed; the larger and shallower the earthquake, the bigger the potential tsunami. Once generated, the waves split: A distant tsunami travels out into the open ocean, while a local tsunami travels toward the nearby coast. The speed of the waves depends on the depth of the water, but typically, waves roll across the ocean at speeds between 400 and 500 mph.

It’s not only the method of generation that differentiates tsunamis from wind-generated waves. On average, wind waves have a crest-to-crest wavelength—the distance over which the wave’s shape repeats—of approximately 330 feet and a height of 6.6 feet. A deep ocean tsunami will have a wavelength of 120 miles and amplitude (the distance from the peak of the wave to its trough) of only about 3.3 feet. This is why tsunamis are difficult to detect in the open ocean.

As a tsunami approaches the shore, the wave compresses: Its speed and wavelength decrease while its amplitude grows enormously. Most waves arrive on-shore not as a huge wave but as a fast-moving tidal bore that floods the shoreline. However, if the trough of the wave arrives before the ridge, or peak, the sea will recede from the shore, exposing normally submerged areas, as the trough builds into a ridge. This can serve as a brief warning that a tsunami is about to occur.

Other causes of tsunamis include underwater landslides and explosions. Another type of wave, called a mega-tsunami, is caused by above-water landslides or glacier calving. The largest recorded mega-tsunami struck in Alaska’s Lituya Bay in 1958; an earthquake triggered a landslide that displaced so much water that the waves created were 470 feet taller than the Empire State Building.

MONITORING WAVES

Like earthquakes, tsunamis can’t be predicted—but that doesn’t mean scientists aren’t trying to figure out ways to warn people before the flooding starts. Using a system of buoys called DART—Deep-Ocean Assessment and Reporting of Tsunamis—researchers can monitor ocean wave height in real time. When an earthquake occurs that scientists believe is likely to trigger a tsunami, these strategically placed buoys send reports on sea level change back to tsunami warning centers. There, scientists use that data to create a model of the potential tsunami’s effects and decide whether to issue a warning or make populations evacuate.

In the 2012 action film Battleship, the DART system took a star turn. Director Peter Berg used it as a method of creating the game’s iconic grid. (The Hollywood version of DART is much more robust than the real-world version, which has just 39 buoys.)

LOCATION, LOCATION, LOCATION

Tsunamis are mostly generated by quakes that occur in subduction zones: areas where denser oceanic plates slide underneath lighter continental plates, causing vertical displacement of the seafloor and water column above it. The majority of the world's subduction zones are in the Pacific Ocean bordering Oceania, Asia, North America, and South America. This highly unsettled loop is nicknamed the "ring of fire" for its concentration of geologic upheavals.

Because the Atlantic Ocean has far fewer subduction zones than the Pacific, Atlantic tsunamis are rare, but possible. The most likely cause would be an earthquake creating a submarine landslide that would displace a huge volume of water and trigger the wave.

In 2001, geophysicists Steven N. Ward and Simon Day suggested that an Atlantic mega-tsunami could be generated by a massive landslide off La Palma, the most active volcano in the Canary Islands archipelago. The theory was based on modeling a number of worst-case scenarios, the authors said. Others have argued that the danger is overblown.

Great White Sharks May Have Led to Megalodons' Extinction

iStock.com/cdascher
iStock.com/cdascher

The megalodon has been extinct for millions of years, but the huge prehistoric shark still fascinates people today. Reaching 50 feet long, it's thought to be the largest shark to ever stalk the ocean, but according to a new study, the predator may have been brought down by familiar creature: the great white shark.

As Smithsonian reports, the analysis, published in the journal PeerJ, finds that the megalodon may have vanished from seas much earlier that previously believed. Past research showed that the last megalodons died roughly 2.6 million years ago, a time when other marine life was dying off in large numbers, possibly due to a supernova blasting Earth with radiation at the end of the Pliocene epoch.

A team of paleontologists and geologists revisited the fossils that this conclusion was originally based on for their new study. They found that many of the megalodon remains had been mislabeled, marked with imprecise dates, or dated using old techniques. After reassessing the specimens, they concluded that the species had likely gone extinct at least 1 million years earlier than past research indicates.

If the megalodon vanished 3.6 million years ago rather than 2.6 million years ago, it wasn't the victim of supernova radiation. One known factor that could explain the loss of the 13 million-year-old apex predator at this time is the rise of a new competitor: the great white shark. This predator came on the scene around the same time as the megalodon's decline, and though a full-grown great white shark is less than half the size of a mature megalodon, the species still would have been a stressor. Adult great whites likely competed with juvenile megalodons, and with the megalodon's favorite prey—small whales—becoming scarce at this time, this may have been enough to wipe the megalodons from existence.

Even if great white sharks eventually beat megalodons for dominance in the oceans, the megalodon's status as one of the most fearsome predators of all time shouldn't be contested. The giant sharks had 7-inch teeth and a bite stronger than that of a T. rex.

[h/t Smithsonian]

From Squatty Potty to Squat-N-Go: The Best Toilet Stool for Every Bathroom

iStock.com/eldemir
iStock.com/eldemir

In 2015, Squatty Potty's bathroom stool plopped into the popular conscience with a viral commercial that featured a unicorn joyfully pooping out a conveyor belt's worth of ice cream. The video racked up more than 35.9 million views on YouTube and reportedly caused a 600 percent jump in sales. "The stool for better stools" was a hit.

Now, it's a hit with the medical community, too. New research out of Ohio State University finds that the toilet stool—which aims to relax the puborectalis muscle and straighten out the rectum, making it easier to poop—really does help people who strain to empty their bowels. The study, published in the Journal of Clinical Gastroenterology's March 2019 issue, only involved 52 people, but it's the first clinical research into the Squatty Potty, and the results were very positive—71 percent of participants said they experienced faster bowel movements after using the stool for a month. A full 90 percent said they experienced less straining than before.

Since the Squatty Potty debuted, the company has inspired plenty of copycats, as well as launching a number of other official Squatty Potty design iterations targeted at every type of user. Here are the best toilet stool options for every bathroom.

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1. If You're Hesitant to Commit: The Squatty Potty Original

At just $25, the original Squatty Potty is a great entry-level option that will allow you to try out the system without sinking a ton of money into it. (And it's a whole lot cheaper than an endless supply of Metamucil.) The white plastic isn't the most elevated decor option, but it's durable, easy to clean, and relatively unobtrusive. It's available in a 7-inch-tall version for standard toilets or a 9-inch-tall version for comfort-height porcelain thrones. If you're not sure how tall your toilet is, the company makes an adjustable height Squatty Potty that can be configured to fit anywhere.

Buy it on Amazon, from Squatty Potty's website for $25, or at these other retailers:

2. If Your Bathroom is Tiny: The Squatty Potty Curve

The original Squatty Potty can be a bit clunky, but a newer version offers all the health benefits without taking up as much space. The Curve has a thinner footprint so that it doesn't stick out quite so far from under your toilet, but still has just enough room for your feet. The 7-inch stool comes in white, pink, black, and gray.

Buy it for $25 on Squatty Potty's website.

3. If You Text on the Toilet: The Keeney Bathroom Stool

A white and blue Keeney toilet stool
Keeney, Amazon

Keeney's toilet stool offers a few unusual features. For one, it has a storage bin designed to keep your wet wipes close at hand. More importantly, it's designed to hold up more than just your feet—it has a smartphone/tablet holder, too. Though toilet stools are designed to make your bowel movements speedier, if you're the kind of person who likes to spend a lot of time on the can, you can also tuck your smartphone into the built-in groove in the stool designed to keep your screen at optimal viewing angles. Whether you're watching Netflix or looking at Tinder, it offers a hands-free option that you're not going to find on any brand-name Squatty Potty. Ergonomically, it's also got slightly angled footrests designed to put you in the optimal pooping position.

Buy it on Amazon for $21.

4. If You're Into Minimalist Design: The Squatty Potty Slim

Great bowel movements and great interior design don't have to be mutually exclusive. Squatty Potty's high-fashion option may be pricier, but it doesn't have the medical-device vibes of the original model, either. Designed for small, urban apartments, it's a bit bigger than the Curve but a lot more aesthetically pleasing. The teak finish is great if you're going for a Scandinavian minimalist vibe, while the acrylic glass Slim Ghost model has an artsy mid-century modern look.

Buy the Slim Teak or the Slim Ghost on Squatty Potty's website for $60 and $80, respectively, or on Amazon for $80 or $83.

5. If You Need to Go on the Go: Squat-N-Go Bamboo X Toilet Stool

While Squatty Potty does make a portable version of its bathroom stool (the cleverly named Porta-Squatty), the most convenient travel stool is made by a competitor. Squat-N-Go's foldable footstool comes in two different pieces for easy storage and portability. The two bamboo platforms essentially act as stilts, propping up your feet separately. They offer the most customizable fit, with 7-inch, 8-inch, and 9-inch heights and the ability to place each footstool anywhere around the toilet, at any angle. When you're done, they fold down to just an inch tall and can be stowed in the included travel bag.

Buy it on Amazon for $40 or at these other retailers:

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