25 Things You Didn't Know About the World's Oceans

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iStock

In 2008, the United Nations recognized World Oceans Day on June 8 as a time to celebrate the immense bodies of water that make up roughly 70 percent of the surface of the Earth. The goal of the day is to promote conservation efforts and engage activists in preserving these five crucial areas—the Pacific, Atlantic, Indian, Arctic, and Southern (Antarctic) Oceans—and their inhabitants.

If you don’t know much about the deep blue sea—like why it's not actually blue, for example—check out 25 facts we’ve culled about the world’s largest and most fascinating real estate.

1. THE SUN GIVES IT THAT BLUE TINT.

A look at calm, blue ocean waters
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One of the most indelible features of the oceans is the deep blue waters that are continually churning, rolling, and coming in waves. The color is the result of the sun’s red and orange wavelengths being absorbed by the surface and its blue wavelengths penetrating deeper, giving way to a blue tint. And because those wavelengths can travel further down, the ocean will tend to appear more blue the lower you go. Why isn't water in a glass blue when you're sitting outdoors? There aren't enough molecules to absorb the light.

2. THEY'RE KEEPING THE INTERNET ONLINE.

If you could catch sight of the miles of cable criss-crossing the world’s oceans, it would look like a giant, submerged web. Communications companies maintain international connections by feeding cables down to (hopefully) flat surfaces on the ocean floor. Some require shark-proof layers to prevent predators from biting into your Netflix stream (although the danger of sharks has been vastly overhyped—human activity is a far bigger threat).

3. THE DEEPEST PART IS REALLY, REALLY DEEP.

The Mariana Trench is considered to be the deepest part of the world’s oceans. Inside of the Trench is a valley known as Challenger Deep that extends roughly seven miles (36,070 feet) below the surface. For comparison, the entirety of Mount Everest—at 29,029 feet—could easily be accommodated there. Manned explorations haven’t gone any further than 35,797 feet below the surface, a record set by two oceanographers in 1960. In 2012, filmmaker James Cameron explored roughly the same depths in a solo mission. It’s considered the deepest point on Earth.

4. SOUNDS CAN TRAVEL TO THE DEEPEST EXPLORED AREAS.

Researchers once lowered an underwater microphone called a hydrophone to almost the bottom of the Mariana Trench to see what sounds—if any—it might pick up. After feeling relieved the immense pressure at those depths—about 8 tons per square inch—didn’t implode the equipment, they discovered that sound from earthquakes, passing baleen whales, and other ambient noise was audible.

5. LAKES AND RIVERS LIE BENEATH THE SURFACE.

Some surfaces in the ocean feature sights that don’t seem to make any logical sense—rivers and lakes, some of them miles long, can stretch across the ground even though they’re submerged. How can a body of water exist in a body of water? Water from under the sea floor seeps up and dissolves salt layers, forming depressions. Because the water in the depression is more dense than the water all around it, it settles into the depression and forms a distinct pool.

6. THERE ARE 20 MILLION TONS OF UNTOUCHABLE GOLD IN THE OCEANS.

If you’re hoping to find a fortune in gold prospecting, don’t expect the ocean to cooperate. You may be able to plunder a shipwreck, but you won’t be able to collect much of the 20 million tons of gold estimated to exist in the water. That’s because it’s so diluted that it’s measured in parts per trillion. One liter of seawater might net you a 13-billionth of a gram.

7. WE KNOW MORE THAN YOU MIGHT EXPECT.

A dolphin swims in the ocean
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You might see mentions that we’ve "mapped" more of Mars than we have the Earth’s oceans, but that’s not quite true. Oceanographers have been able to visualize almost 100 percent of the ocean floors, albeit in a resolution that makes it difficult to spot a lot of detail. In that sense, images of Mars and other planets have been able to offer more information because they’re not covered in water that can block radar. Although we haven't explored the vast majority of the oceans first-hand, technology has enabled us to have a rough idea of their layouts.

8. THE BIGGEST WATERFALL ON EARTH IS IN THE ATLANTIC.

Putting Niagara Falls to shame is the Denmark Strait, a waterfall below the Atlantic Ocean that, in terms of water volume, is the equivalent of 2000 of the world’s most notable waterfalls, with cascading liquid pouring 11,500 feet down. The Strait’s cold water on the eastern side is more dense than the warm fluid coming from the west. When the two waters mix, the colder supply sinks, creating a waterfall.

9. WE DON'T KNOW ANYTHING ABOUT MOST OF THE MARINE LIFE.

An octopus is photographed by an ocean photographer
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Size and water pressure conspire to limit our exploration of the oceans, so much so that it’s estimated we’ve identified only one-third of the potential marine life lurking beneath the surface. It’s possible most of those are smaller organisms, but it’s likely that some whales and other mammal species have yet to be discovered. We’re making progress, though: An average of 2000 new species are described each year.

10. MAGELLAN NAMED THE PACIFIC OCEAN.

When Ferdinand Magellan crossed the Atlantic beginning in 1519, he eventually found his way to another body of water—what he dubbed the Pacific, or peaceful, ocean due to the calm surface. He didn’t know it at the time, but the Pacific would eventually be recognized as the largest ocean on the planet at 59 million square miles.

11. THE MOST REMOTE PLACE ON EARTH IS IN THE SOUTH PACIFIC.

Point Nomo is illustrated
Courtesy National Oceanic and Atmospheric Administration

Known as Point Nemo, the area is roughly 1000 equidistant miles away from the coasts of three neighboring islands and so remote that astronauts are often closer to any theoretical occupants than anyone on dry land.

12. MOST VOLCANIC ERUPTIONS ARE UNDERWATER.

Up to 80 percent of volcanic eruptions go unnoticed by land-dwellers. That’s because they’re erupting underwater. An estimated one million volcanoes—some extinct and some very active—spew molten hot lava. Despite the heat, creatures can still be found near their superheated vents. Researchers believe these areas harbor several undiscovered species that are invulnerable to the harsh conditions, including water temperatures up to 750 degrees Fahrenheit.

13. THERE MAY BE BILLIONS IN SUNKEN TREASURE DOWN IN THE DEEP.

A sunken ship sits on the ocean floor
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It’s impossible to offer an accurate estimate of how many shipwrecks and accompanying treasures are lurking in the oceans, but a few people have made an honest effort of it. The National Oceanic and Atmospheric Administration (NOAA) thinks a million sunken ships lurk in the dark; others peg the total value of the unrecovered treasures at $60 billion. So why don’t we hear more stories of watery grave-robbing? Because governments or private parties are likely to make a legal claim to those funds, making an expensive expedition for treasure a gamble at best.

14. THEY KEEP US BREATHING.

Forget all the beauty and wonder of the world’s oceans: At the bare minimum, they’re responsible for supplying us with oxygen. Oceans produce 70 percent of the oxygen supply in the atmosphere thanks to marine plants releasing it as a byproduct of photosynthesis. One phytoplankton, Prochlorococcus, is estimated to be solely responsible for one in every five breaths a human will take.

15. "DEAD ZONES" CAN BE BARREN OF ANY LIFE.

Dark ocean waters can be devoid of life
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One reason pollution is such an issue for oceans: It can rob them of the oxygen needed to support life. When run-off from waste disposal gets into the water, it can feed an overabundance of algae, which then dies, sinks, and as it decomposes, consumes the available oxygen in the water. That creates hypoxic areas, or hot spots with a lack of oxygen. If fish and other marine life don’t find a new space to dwell in, they’re toast.

16. THE FISH ARE EATING A LOT OF PLASTIC.

With over seven million tons of plastic winding up in the ocean each year, it’s inevitable that a lot of it winds up as part of an unwelcome addition to a fish’s diet. For fish in the northern Pacific, researchers at the University of California, San Diego once estimated they swallow between 12,000 and 24,000 tons every year.

17. KEEPING TROPICAL PET FISH MIGHT BE HARMING THE OCEANS.

Colorful tropical fish swim in the water
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Those aquariums in pet stores and dental offices might remind you of marine life, but they might also be having a negative impact. When tropical fish are caught, fishermen use sodium cyanide to make them float out of the reef for easy scooping. While the hope is that it just stuns them, the residue of the chemical can bleach coral reefs and kill scores of other fish.

18. TSUNAMI WAVES CAN REACH 100 FEET...

When waves reach shallow water near land, energy that would normally be dispersed goes up, elongating the wave. A 1958 earthquake and landslide in Alaska generated a tsunami 100 feet high and destroyed all vegetation up to 1720 feet, the largest in recorded history.

19. ...BUT THE BIGGEST WAVES ARE UNDER THE SURFACE.

Called internal waves, these water walls have been found three miles below the surface. The waves are part of water layers with different densities and can reach heights of 800 feet before collapsing. Scientists believe these massive forces can help move heat and nutrients to other areas.

20. WE'RE TRYING TO MAKE THE OCEAN DRINKABLE.

As most everyone knows, drinking salt water is perilous at best and deadly at worst. In a process called desalination, that salt is removed, leaving fresh water. But building facilities and the energy required to process water this way has traditionally been more expensive than sourcing water from potable sources.

21. THE BRISTLEMOUTH IS THE MOST ABUNDANT VERTEBRATE IN THE WORLD.

A bristlemouth snacks on a shrimp
Courtesy National Oceanic and Atmospheric Administration

Not familiar? If you saw one, you’d know. The bristlemouth is a fish a little smaller than your average human finger that has a mouth full of fangs and can glow in the dark. It’s also the most common vertebrate in the world. For comparison? Chickens could number as many as 24 billion on land, while bristlemouths are said to add up to the hundreds of trillions.

22. GIANT KELP GROWS VERY QUICKLY.

Giant kelp, or Macrocystis Pyrifera, is a type of seaweed that experiences an astonishing growth spurt. To reach its usual height of 100 feet, the species can grow up to two feet in a single day.

23. RUBBER DUCKS HAVE HELPED OUR UNDERSTANDING OF THE OCEANS.

A rubber duck floats in the water
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In 1992, a shipment of bath toys was headed from China to the U.S. when the cargo ship dropped a container. More than 28,000 rubber ducks—or duckies, depending on your preference—and other play-animals were dumped into the North Pacific Ocean. Oceanographers tracked where the ducks wound up in order to better understand the water currents, with some landing ashore in Europe and Hawaii. The duck sightings didn’t ease up until the mid-2000s.

24. ANTARCTIC FISH HAVE NATURAL ANTIFREEZE.

Curious how aquatic life can survive the temperatures at the poles? Antifreeze proteins in the fish prevent ice crystals from growing, preventing their blood from being overcome by the chill and allowing it to continue flowing.

25. SEASHELLS DON'T ACTUALLY SOUND LIKE THE OCEAN.

A child holds a seashell up to her ear
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Seashells have long been perceived as the iPods of the sea, tiny little devices that can mimic the static, hissing noise of the water. What they’re actually doing is acting as a resonator, or a cavity that allows sound to vibrate. By holding up the shell to your ear, you’re hearing the ambient noise around you amplified. All that whooshing air typically sounds a lot like the movement of cascading waves. If you can't make it to beach, though, it might be the next best thing.

Could Gigantic Coconut Crabs Have Played a Part in Amelia Earhart’s Mysterious Disappearance? At Least One Scientist Thinks So

Getty Images
Getty Images

Amelia Earhart's disappearance during her attempt to fly around the world has captivated historians and conspiracy theorists for more than 80 years. One organization is now suggesting that her fate may have been sealed by giant crabs.

The International Group for Historic Aircraft Recovery (TIGHAR) believes that Amelia Earhart and navigator Fred Noonan may have landed their plane on Nikumaroro Island when they couldn't find their target, Howland Island, and that Nikumaroro's endemic crustaceans may have played a part in the ensuing mystery.

According to National Geographic, there are several clues supporting TIGHAR's theory. The large reef that hugs Nikumaroro’s coast makes it conducive to emergency aircraft landings. In 1940—just three years after Earhart’s disappearance—British colonists found 13 human bones beneath a ren tree on the island and shipped them to Fiji, where they were lost. The colony's administrator, Gerald Gallagher, sent a telegram back to England positing that it was Earhart’s skeleton. Then, in 2001, researchers uncovered U.S.-made artifacts around the ren tree including a jackknife, a woman’s compact, a zipper, and glass jars. The plot thickened even further in 2017, when four forensic bone-sniffing dogs all indicated that a human had indeed died at the site, though excavators failed to dig up any more evidence.

If those 13 bones beneath the ren tree did belong to the unfortunate castaway, where are the rest of her remains? Tom King, TIGHAR’s former chief archaeologist, thinks that coconut crabs can answer that question.

Nikumaroro is home to thousands of the colossal creatures, which can grow to a terrifying 3 feet across and weigh 9 pounds. They’re sometimes called robber crabs because of their penchant for absconding with objects that smell like food, and they’ll eat practically anything—coconuts, fruit, birds, rodents, other crabs, their own discarded body parts, and carrion.

It’s not unreasonable, then, to think that coconut crabs may have feasted on Earhart’s corpse and then taken her bones home with them. In one experiment to test the theory, TIGHAR researchers deposited a pig carcass on the island and filmed the aftermath. With the help of small strawberry hermit crabs, coconut crabs stripped the pig down to the bone in two weeks. After a year, some of the bones had been dragged 60 feet from the carcass’s original location, and some were never recovered at all.

King believes Earhart’s missing 193 bones could be hidden in the burrows of various coconut crabs. As in the pig experiment, crabs may have scattered some of Earhart’s bones dozens of feet away, but maybe not all of them—after all, the forensic dogs smelled bones near the ren tree that haven’t yet been located. Right now, TIGHAR is working with the Canine Forensics Foundation to further explore the area.

While we wait for more answers, dive into these other theories about Earhart’s disappearance.

[h/t National Geographic]

10 Juicy Facts About Leeches

Ian Cook
Ian Cook

Leeches get a bad rap, but they’re actually pretty cool once you get to know them—and we're finding out more about them, even today. Recently, a team led by Anna Phillips, curator of parasitic worms at the Smithsonian National Museum of Natural History, discovered a new species of medicinal leech (pictured above) in a Maryland swamp. We asked parasite expert and curator at the American Museum of Natural History Mark E. Siddall to share some surprising facts about the worms we love to hate. 

1. Not all leeches suck blood.

Hematophagous, or blood-feeding, species are only one type of leech. “The vast majority of species are [hematophagous],” Siddall tells Mental Floss, “but it depends on the environment. In North America, there are probably more freshwater leeches that don’t feed on blood than there are blood-feeders.” And even among the hematophagous species, there are not too many who are after you. “Very few of them are interested in feeding on human blood,” Siddall says. “Certainly they’ll do it, if they’re given the opportunity, but they’re not what they’re spending most of their time feeding on.” 

2. Leeches are everywhere.

Japanese leech on a log
Pieria, Wikimedia Commons // Public Domain

“Every continent on the planet has leeches, with the exception of Antarctica,” Siddall says. “And even then there are marine leeches in Antarctic waters.” Humans have co-existed with leeches for so long, according to Siddall, that just about every language has a word for leech. 

3. Leeches have made a comeback in medicine.

Bloodletting for bloodletting’s sake has fallen out of favor with Western physicians, but that doesn’t mean medicinal leeches are enjoying a cushy retirement. Today, surgeons keep them on hand in the operating room and use them as mini-vacuums to clean up blood. “That is a perfectly sensible use of leeches,” Siddall says. Other uses, though, are less sensible: “The more naturopathic application of leeches in order to get rid of bad blood or to cure, I don’t know, whatever happens to ail you, is complete hooey,” he says. How on Earth would leeches take away bad blood and leave good blood? It’s silly.” 

4. Novelist Amy Tan has her own species of leeches.

Land-based leeches made an appearance in Tan’s 2005 book Saving Fish from Drowning, a fact that instantly put the author in leech researchers’ good graces. “There are not a lot of novels out there with terrestrial leeches in them,” Siddall says. So when he and his colleagues identified a new species of tiny terrestrial leeches, they gave the leech Tan’s name. The author loved it. “I am thrilled to be immortalized as Chtonobdella tanae,” Tan said in a press statement. “I am now planning my trip to Queensland, Australia, where I hope to take leisurely walks through the jungle, accompanied by a dozen or so of my namesake feeding on my ankles.”

5. Leeches can get pretty big.

The giant Amazon leech (Haementeria ghilianii) can grow up to 18 inches and live up to 20 years. And yes, this one’s a blood-feeder. Like all hematophagous species, H. ghilianii sticks its proboscis (which can be up to 6 inches long) into a host, drinks its fill, and falls off. Scientists thought the species was extinct until a zoologist found two specimens in the 1970s, one of whom he named Grandma Moses. We are not making this up.

6. Leeches make good bait.

Many walleye anglers swear by leeches. “A leech on any presentation moves more than other types of live bait," pro fisher Jerry Hein told Fishing League Worldwide. "I grew up fishing them, and I think they're the most effective live bait around no matter where you go." There’s an entire leech industry to provide fishers with their bait. One year, weather conditions kept the leeches from showing up in their typical habitats, which prevented their collection and sale. Speaking to CBS news, one tackle shop owner called the absence of leeches “the worst nightmare in the bait industry.”

7. Leech scientists use themselves as bait.

Siddall and his colleagues collect and study wild leeches. That means hours of trekking through leech territory, looking for specimens. “Whether we’re wandering in water or traipsing through a bamboo forest,” Siddall says, “we are relying on the fact that leeches are attracted to us.” Do the leeches feed on them? “Oh my god, yes. We try to get them before they feed on us … but sometimes, obviously, you can’t help it.”

8. Leech sex is mesmerizing.

Like many worms, leeches are all hermaphroditic. The specifics of mating vary by species, but most twine themselves together and trade sperm packets. (The two leeches in the video above are both named Norbert.)

9. Some leech species make surprisingly caring parents. 

“There’s a whole family of leeches that, when they lay their eggs, will cover them with their own bodies,” Siddall says. “They’ll lay the eggs, cover them with their bodies, and fan the eggs to prevent fungus or bacteria from getting on them, and then when the eggs hatch, they will attach to the parent. They’re not feeding on the parent, just hanging on, and then when the parent leech goes to its next blood meal it’s carrying its offspring to its next blood meal. That’s pretty profound parental care, especially for invertebrates.”

10. You might be the next to discover a new leech species. 

Despite living side-by-side with leeches for thousands of years, we’ve still got a lot to learn about them. Scientists are aware of about 700 different species, but they know there are many more out there. “I’ll tell you what I wish for,” Siddall says. “If you ever get fed on by a leech, rather than tearing off and burning it and throwing it in the trash, maybe observe it and see if you can see any color patterns. Understand that there’s a real possibility that it could be a new species. So watch them, let them finish. They’re not gonna take much blood. And who knows? It could be scientifically useful.”

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