Wedged between two Norwegian islands, the strait of Saltstraumen is home to a truly awe-inspiring natural occurrence.

For more than two millennia now, an astonishing event has regularly manifested off the coast of Norway. Four times each and every day, a set of vortices open up in the waters of the county of Nordland. And according to experts, this phenomenon is the most powerful occurrence of its kind.

A little over six miles away from the Nordland region known as Bodø, a strait called Saltstraumen lies between two fjords. These are called Saltfjorden and Skjerstad Fjord. In simple terms, a fjord is a slim section of water, formed by a glacier, which is wedged between cliffs.

Measuring just under two miles in length and 490 feet in width, the Saltstraumen strait is by no means considered large. Yet even so, every six hours around 110 billion gallons of water surge through it. It is therefore known to possess one of the most powerful currents anywhere on Earth.

The water traveling through the Saltstraumen strait can attain tremendous speeds of almost 23 miles per hour. And when the currents there are at their most significant, a series of swirling tunnels materialize in the water. These long, briny spirals are what we refer to as whirlpools or maelstroms.

A whirlpool occurs when the direction or course of underwater currents is disrupted. Basically, it manifests as a spiral of spinning water which can appear to resemble a sort of downward passageway. We can actually see smaller examples of whirlpools when water from a bath travels down a drain.

A maelstrom is simply the term used for the more forceful whirlpools which can materialize in oceans. It’s apparently a Nordic phrase which itself might have derived from the Dutch word maalstroom, translating as “crushing current.” It may also have roots in the Swedish language, where the word malström translates roughly as “grinding current.”

For English speakers, however, the word “maelstrom” first appeared in a short story by acclaimed author Edgar Allan Poe. Published in 1841, “A Descent into the Maelström” appeared within a title known as Graham’s Magazine. Poe himself actually served as the editor of this magazine for a time.

In “A Descent into the Maelström,” a man recalls his terrible experiences having come across a gargantuan whirlpool. The character has apparently aged prematurely due to his encounter and expresses great terror at the memory of it. The story was supposedly inspired by a real-life complex of whirlpools called the Moskstraumen, which is actually located near Saltstraumen.

In the same century as “A Descent into the Maelström,” a number of other stories appeared which referenced whirlpools. Indeed, ten years after the 1841 publication of Poe’s story came Herman Melville’s Moby-Dick. And Twenty Thousand Leagues Under the Sea by French author Jules Verne was published in 1870.

Maelstroms, however, have been a source of great curiosity for far longer than a mere few centuries. In fact, even some of the myths of ancient Greece have touched upon the notion of these vortices. And we can see this if we consider the monstrous entity known as Charybdis.

One telling of the myth of Charybdis presents the figure as the daughter of the gods Gaia and Poseidon. Gaia, on the one hand, is presented as being the goddess of the Earth. Whereas Poseidon is described as the deity of the sea and was therefore said to look after sailors.

According to legend, Poseidon was once embroiled in a conflict with his brother, the deity known as Zeus. Charybdis entered the fray on the side of her father and aided him in covering some lands with water. This angered Zeus, who then took Charybdis and condemned her to bottom of the sea.

A curse then befell Charybdis which saw her transform into a great hulking water monster. Now described as a hideous creature with flippers, she perpetually drank the waters of the sea. And, according to myth, this act of drinking led to the formation of whirlpools in the ocean.

Greek mythology further also claims that Charybdis lived very close to another vicious sea creature known as Syclla. A sort of rock monster, Syclla was also a threat to sailors – just like Charybdis. Therefore, danger lurks when veering too closely to either one of them.

The legend of these two monsters actually led to the creation of a popular idiom, “Between Scylla and Charybdis.” This basically relates to deciding on a course of action when given a choice between two undesirable options. In other words, does one travel the oceans by passing close to deadly rocks or a whirlpool?

So it seems that whirlpools have managed to capture the imaginations of storytellers throughout the millennia. Yet even though they’re often the cause of huge levels of destruction in these tales, in reality they’re much more tame. But that’s not to say that they aren’t a threat to smaller craft or swimmers passing nearby.

For instance, French Pass is a body of water that lies between the two main islands of New Zealand. The currents there are famously strong and are even capable of overwhelming fish into a daze. And in the year 2000 they were actually responsible for the deaths of a number of people.

A group of students had been swimming through the pass as part of a scuba diving expedition. However, some got caught up in the pull of the tides and then got drawn into a whirlpool. The maelstrom reportedly dragged them some 292 feet underwater and resulted in several of the divers deaths.

Elsewhere, a group of documentary filmmakers in Scotland explored the potential dangers to human life caused by whirlpools. Indeed, the focus of their curiosity was the Corryvreckan whirlpool. This has been claimed as one of the top three biggest whirlpools found on the whole of planet Earth.

The Corryvreckan whirlpool, as its name might suggest, is located within the Gulf, or Strait, of Corryvreckan. This stretch of water lies in the middle of two islands called Scarba and Jura. These islands, in turn, are in the sea just west of the shores of the Scottish mainland.

The name of this gulf derives from the Gaelic term Coire Bhreacain. Possible translations for the term include “cauldron of the plaid,” and “cauldron of the speckled seas.” According to Scottish legend, this gulf is where a deity named Cailleach Bheur used to clean an item of clothing.

Apparently, the great roar from the Corryvreckan whirlpool is audible around ten miles from its source. And a sailing manual titled Admiralty Sailing Directions: West Coast of Scotland Pilot has referred to the waters there as being “very violent and dangerous.” Moreover, the book warns that “no vessel should attempt this passage without local knowledge.”

Yet in any case, the documentary makers wanted to reach their own conclusions regarding the threat of the whirlpool. And so they tossed a lifejacket-wearing dummy carrying a device for measuring depth into the gulf. And the dummy was very quickly sucked into the vortex.

The dummy later reappeared along the shore. The lifejacket, it seemed, had been powerless against the strength of the maelstrom. The group then studied the findings recorded by the depth-measuring device. And they found that the dummy had been pulled around 860 feet underwater.

This rather informal experiment illustrates how dangerous a maelstrom is for human beings caught in its pull. However, the lethal hazards of these water vortices are quite limited. But when a whirlpool is created by humans, the consequences can actually prove far more devastating.

Back November 1980, a group of oil workers under contract with Texaco were working on Lake Peigneur in Louisiana. Due to a positioning error, the workers accidentally drilled into the wrong place and thereby initiated a disaster. The mistake created a void at the bottom of the lake and the waters flooded into it.

This drainage of the lake’s waters into the hole created by the workers resulted in an enormous maelstrom. The whirlpool then managed to drag 11 barges, multiple trees, surrounding land and even the drilling platform itself underwater. Somehow, though, there were no human fatalities – but a number of dogs reportedly weren’t so lucky.

Yet despite rare disasters such as the one on Lake Peigneur, the vast majority of maelstroms are natural occurrences. And examples of the phenomena are visible in waters the world over. In North America, for instance, two particularly large examples exist just off the coast of Canada.

Old Sow is a massive whirlpool in the water between Canada’s Deer Island and Moose Island in the U.S. state of Maine. It apparently forms a vortex which can measure up to around 250 feet across. The name “Old Sow” reportedly derives from the fact that the noise coming from the maelstrom sounds like a pig.

Meanwhile, whirlpools also materialize in the Skookumchuck Narrows, a strait in Canada’s Sunshine Coast region. The currents created there capable of reaching speeds of more than 18 miles per hour. The consequent rapids are, in turn, thought by some to be the world’s quickest.

The largest natural whirlpool on Earth, however, is said to be Norway’s Saltstraumen maelstrom. This is actually a complex of multiple whirlpools which appear together and morph into and away from one another. The strait itself is over 2,000 years old, the result of a geographical event in the wake of glacial activity.

The Saltstraumen strait joins Norway’s Skjerstad Fjord together with Saltfjorden. The current for which the strait is famous happens when tidal forces attempt to fill in the Skjerstad Fjord. Tides, in effect, are the changes in sea level which occur because of the Moon’s gravitational pull.

So in other words, the strength of the current at Saltstraumen depends on the phase of the Moon. If the satellite appears large in the sky, then the current will be at its most powerful and spectacular. Therefore, the best time to observe the natural maelstrom is during a full moon.

For those looking to observe the Saltstraumen maelstrom, however, it can be difficult to time it correctly. Arriving around a full moon is a good start, of course, but the specific times of its appearance can fluctuate. On the other hand, it shows up four times each day – so it’s not exactly rare.

The Saltstraumen maelstrom is apparently visible from the edge of nearby land. The optimum place to catch a glance of the phenomenon, however, would probably be from somewhere above it. Thankfully, there’s no need for flying equipment to achieve this perspective, as it can be provided by the Saltstraumen Bridge.

First opened back in 1978, the Saltstraumen Bridge connects two Norwegian islands which are known as Straumøya and Knaplundsøya. The prestressed concrete structure measures up at 2,520 feet in length and 37 feet in width. It’s made up of ten individual spans, the longest of which is reportedly 520 feet long.

The Saltstraumen Bridge gives curious tourists the chance to catch a glimpse of this powerful natural occurrence. And a number of companies located in the area offer boat tours to allow for sea-level perspective of the phenomenon. Yet the Saltstraumen maelstrom is an attractive prospect for more than just inquisitive human beings.

The conditions present at the Saltstraumen strait have, in fact, attracted an abundance of plankton. This is defined as a group of generally small water-based organisms which act as food for larger creatures. The presence of plankton in a body of water can, in turn, cause large numbers of fish to inhabit the area.

The large quantities of fish in Saltstraumen have made the region a popular fishing spot today. But the area seemingly has a history of the tradition, as evidenced by the discovery of an ancient human settlement there. It seems that people once inhabited the lands close to the sea, perhaps drawn there by the numerous fish.

So the Saltstraumen strait and its surrounding areas possess an extremely rich history, stretching back many thousands of years. But ultimately, the most compelling aspect of the area is the tremendous maelstrom which comes into being there everyday. And though it might not be as dramatic as the maelstroms of mythology, it’s nonetheless capable of inspiring genuine awe.