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

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.

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NOAA, Wikimedia Commons // Public Domain
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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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Penn Vet Working Dog Center
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Stones, Bones, and Wrecks
New Program Trains Dogs to Sniff Out Art Smugglers
Penn Vet Working Dog Center
Penn Vet Working Dog Center

Soon, the dogs you see sniffing out contraband at airports may not be searching for drugs or smuggled Spanish ham. They might be looking for stolen treasures.

K-9 Artifact Finders, a new collaboration between New Hampshire-based cultural heritage law firm Red Arch and the University of Pennsylvania, is training dogs to root out stolen antiquities looted from archaeological sites and museums. The dogs would be stopping them at borders before the items can be sold elsewhere on the black market.

The illegal antiquities trade nets more than $3 billion per year around the world, and trafficking hits countries dealing with ongoing conflict, like Syria and Iraq today, particularly hard. By one estimate, around half a million artifacts were stolen from museums and archaeological sites throughout Iraq between 2003 and 2005 alone. (Famously, the craft-supply chain Hobby Lobby was fined $3 million in 2017 for buying thousands of ancient artifacts looted from Iraq.) In Syria, the Islamic State has been known to loot and sell ancient artifacts including statues, jewelry, and art to fund its operations.

But the problem spans across the world. Between 2007 and 2016, U.S. Customs and Border Control discovered more than 7800 cultural artifacts in the U.S. looted from 30 different countries.

A yellow Lab sniffs a metal cage designed to train dogs on scent detection.
Penn Vet Working Dog Center

K-9 Artifact Finders is the brainchild of Rick St. Hilaire, the executive director of Red Arch. His non-profit firm researches cultural heritage property law and preservation policy, including studying archaeological site looting and antiquities trafficking. Back in 2015, St. Hilaire was reading an article about a working dog trained to sniff out electronics that was able to find USB drives, SD cards, and other data storage devices. He wondered, if dogs could be trained to identify the scents of inorganic materials that make up electronics, could they be trained to sniff out ancient pottery?

To find out, St. Hilaire tells Mental Floss, he contacted the Penn Vet Working Dog Center, a research and training center for detection dogs. In December 2017, Red Arch, the Working Dog Center, and the Penn Museum (which is providing the artifacts to train the dogs) launched K-9 Artifact Finders, and in late January 2018, the five dogs selected for the project began their training, starting with learning the distinct smell of ancient pottery.

“Our theory is, it is a porous material that’s going to have a lot more odor than, say, a metal,” says Cindy Otto, the executive director of the Penn Vet Working Dog Center and the project’s principal investigator.

As you might imagine, museum curators may not be keen on exposing fragile ancient materials to four Labrador retrievers and a German shepherd, and the Working Dog Center didn’t want to take any risks with the Penn Museum’s priceless artifacts. So instead of letting the dogs have free rein to sniff the materials themselves, the project is using cotton balls. The researchers seal the artifacts (broken shards of Syrian pottery) in airtight bags with a cotton ball for 72 hours, then ask the dogs to find the cotton balls in the lab. They’re being trained to disregard the smell of the cotton ball itself, the smell of the bag it was stored in, and ideally, the smell of modern-day pottery, eventually being able to zero in on the smell that distinguishes ancient pottery specifically.

A dog looks out over the metal "pinhweel" training mechanism.
Penn Vet Working Dog Center

“The dogs are responding well,” Otto tells Mental Floss, explaining that the training program is at the stage of "exposing them to the odor and having them recognize it.”

The dogs involved in the project were chosen for their calm-but-curious demeanors and sensitive noses (one also works as a drug-detection dog when she’s not training on pottery). They had to be motivated enough to want to hunt down the cotton balls, but not aggressive or easily distracted.

Right now, the dogs train three days a week, and will continue to work on their pottery-detection skills for the first stage of the project, which the researchers expect will last for the next nine months. Depending on how the first phase of the training goes, the researchers hope to be able to then take the dogs out into the field to see if they can find the odor of ancient pottery in real-life situations, like in suitcases, rather than in a laboratory setting. Eventually, they also hope to train the dogs on other types of objects, and perhaps even pinpoint the chemical signatures that make artifacts smell distinct.

Pottery-sniffing dogs won’t be showing up at airport customs or on shipping docks soon, but one day, they could be as common as drug-sniffing canines. If dogs can detect low blood sugar or find a tiny USB drive hidden in a house, surely they can figure out if you’re smuggling a sculpture made thousands of years ago in your suitcase.

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