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And as always, shipping is free! Ever since humans began exploring and trading by sea, we’ve known it can be a dangerous place. And no reminder is more potent than a shipwreck marking the spot where mariners met their tragic end.

Over the centuries, shipwreck graveyards have built up in particular spots around the world, where it seems the waters are exceptionally risky. The forces that create these can be oceanic, atmospheric, or even economic or political. So let’s dive in and look at the science behind these treacherous waters and why these graveyards form where they do.

One of these graveyards is the Graveyard of the Atlantic, located off the coast of North Carolina in the United States. Since the 1500s, this has been the site of around 2,000 shipwrecks, including Spanish galleons, oil tankers, and German U-boats. And some of the shipwreck’s survivors even ended up settling in North Carolina and are the ancestors of people still living there today.

But how the shipwrecks happened in the first place has to do a lot with the currents around there. See, around this graveyard is where the Labrador Current meets the Gulf Stream. And navigators take advantage of these currents to speed up their trips, which brings a lot of ships to this area.

It’s convenient that after following the east coast of North America, the Gulf Stream bends towards Europe, a highway for boats traveling from the Caribbean. Another feature of these currents is that Labrador brings cold water down from the North, and the Gulf Stream brings warm water up from the south. Generally, these currents remain stable because cold water is denser, so it flows underneath the warm water.

But when that process is perturbed, these two can mix, creating turbulence and challenging currents. Combine that with sandbars constantly shifting on top of an already complex shoreline of bays, inlets, and islands, and you have a seafarer’s nightmare. But there’s competition for this nightmare; another contender for the Atlantic’s graveyard is Sable Island off the coast of Nova Scotia, Canada.

This island is near a place where fish are pretty abundant, so it lured lots of ships to this treacherous area, and over 350 have been claimed. For around 125 days a year, this island is hidden in fog, and before radar or GPS, navigation instruments like sextants were the most accurate tool to figure out your location. But to use it, you need to be able to see the sky, a pretty difficult feat with all the dense fog.

So sailors could only estimate their position based on when they took their last accurate reading, so you can imagine how that went. Like many of the spots we’ll talk about, modern technology has done a lot to slow down the wrecks in both graveyards of the Atlantic. There has only been one wreck on Sable island since 1947, and the most recent one in North Carolina, in 2012, had extenuating circumstances related to Hurricane Sandy.

But all in all, it is still way less than before. Heading over to the other coast of the Americas, the Graveyard of the Pacific refers to the dangerous conditions that occur from the northern tip of Vancouver Island down to Oregon off the west coast of North America. In these waters, mariners contend with pretty much everything from harsh Pacific weather, to strong tidal currents, to rocky coastlines.

But the epicenter of this graveyard is likely the Columbia River Bar at the border of Washington and Oregon in the US, where the mighty Columbia River meets the ocean. When Europeans arrived, the wrecks started piling up, eventually reaching around 2000 ships. Big rivers carry lots of sediment, and when they meet a larger body, like the ocean, this sediment falls out of the water and accumulates.

For most large rivers, this eventually builds a delta, a large fan of sediment that slowly dissipates the river’s energy. But the Columbia doesn’t have a delta, so it hits the ocean at nearly full force. Many say it’s like the force of a “firehose” compared to other rivers.

This current collides with ocean waves coming from the other direction making the waters where they meet very unpredictable. While the Columbia has not built a delta, the sediment it carries has built a roughly 5-kilometer wide and 10-kilometer long sandbar extending out from the coast, which can shift rapidly and create another hazard for ships to contend with. But a lot of effort has gone into making this area safer.

Lighthouses were built in the 1850s, followed by jetties made of boulders to guide the current and the sand in the early 1900s. Massive amounts of sediment are also removed every year to help deepen the waterway. And these measures have increased the safe depth for ships from 7 to 12 meters.

If you’d like to see some shipwrecks up close, I got some news: you do not need scuba gear to see these. The shipwrecks of the Aral Sea located in Kazakhstan and Uzbekistan are high and dry in the middle of what is now a desert. But the forces that led to this bizarre sight were not natural; they were political and economic.

The Aral Sea was once the fourth-largest lake in the world. But in the 1950s, the Soviet Union began diverting two rivers flowing into it towards cotton farms instead. This caused the lake to shrink dramatically.

It lost over 80% of its water and split into several smaller lakes, including the North and South Aral Seas. Many areas, particularly in the east, dried up completely, leaving the abandoned boats in the desert as the last reminder of the prolific fishing place it used to be. 48,000 tons of fish were caught in the 1950s, and that went to zero by the late 1980s. And even in places that didn't dry up completely, the remaining water became so salty that many freshwater fish died, and the ecosystem collapsed.

To top all that off, the cotton farms that took the lake’s water also used a lot of pesticides, including the now-banned DDT. This left a barren desert landscape of contaminated salt and sand which can be whipped up by winds creating toxic dust storms. And scientists have traced these contaminants to the blood and breast milk of those living in the area.

Despite the massive scale of this ecological disaster, there has been some recent progress. A dam completed in 2005 has managed to raise the level of the North Aral Sea by over three meters in the first seven months. Salinity has dropped, and fish stocks have improved as a result!

The Skeleton Coast of Namibia was initially named for the sight of bones from the whaling industry. Now, many associate it with the skeletons of ships and even of the unlucky sailors aboard. There are around 500 wrecks along the coast, and a big reason is the way the wind blows.

Winds come from the south along the coast of the continent. But winds don’t transport water in the same direction as they blow. In the Southern hemisphere, a wind blowing towards the North transports water towards the west, away from the shoreline, due to an effect called Coriolis force.

Earth is constantly spinning eastward, so things like air and water at the Earth's surface are deflected slightly as they move. This is also why hurricanes spin counterclockwise in the northern hemisphere and clockwise in the southern! Moving water away from the coast pulls up nutrient-rich cold water from deep in the ocean, a process called upwelling.

These nutrients support a rich ecosystem that brings fishing ships to the area. But when warm air from the continent moves over the upwelled cold water, the moisture in the air condenses, and fog forms. As we’ve seen from a couple of these graveyards, before modern navigation, the dense fog made for a bad time.

Even with modern satellites and GPS, these conditions are challenging. A Japanese fishing ship ran aground in 2018. Perhaps the most famous shipwreck of the Great Lakes is also the most recent, the Wreck of the Edmund Fitzgerald that was immortalized in the folk song of the same name.

But this is one of an estimated up to 6,000 shipwrecks on the Great Lakes, which may have taken a staggering 30,000 lives. Here it comes down to the weather that can suddenly change into fierce storms. The “gales of November”' mentioned in the song begin over the Rockies when cold arctic air from Canada combines with moist low-pressure systems from the Gulf of Mexico.

Then the jet stream acts as an expressway to transport these building systems right over to the Great Lakes, where their relatively warm water can power them to even greater levels. And by greater levels, I mean waves on Lake Superior can easily top out around 8 meters. One of the most haunting lines in the song is that “The lake, it is said, never gives up her dead,” and there’s some science behind this too.

Bodies tend to float once bacteria produce enough gasses to make them buoyant. But the cold waters of the lakes slow bacterial growth and delay them bobbing back up to the surface. Cold, fresh water is also perfect for keeping these wrecks intact.

Even old wooden ships are in near pristine condition. Most of these graveyards occur due to a complex interplay of many different forces. But that wasn’t the case for Ripple Rock off the west coast of Canada.

The problem was just one rock! Well, more like a little undersea mountain that sat in the middle of a very narrow pass between Vancouver Island and Maud Island. Ships just kept hitting it.

In the same way I keep stubbing my pinky toe on the same spot on my dresser! This one rock sank 20 large and over 100 small boats, claiming at least 114 lives. But the advantage to having a single factor behind a ton of shipwrecks is perhaps you can do something about it.

That is easier said than done, though, in 1943 and 1945, attempts to drill into the top of the rock and blast it apart with dynamite failed. So instead, they dug a tunnel down from a nearby island under the seabed and up into the core of the rock itself and filled it with over 1300 tonnes of explosives. In 1958 they hit the button and triggered one of the largest non-nuclear explosions the world has ever seen, sending water and rock over 300 meters in the air.

And it worked! The channel now has over 13 meters of clearance! And ships are no longer harmed.

Shipwreck graveyards are a stark reminder of the dangers of the ocean. Most of these sailors were drawn into hazardous waters just trying to make a living. Luckily, these areas have become a lot safer.

Navigation technology has become more accurate and less expensive, and safety standards such as maximum cargo loads have improved. While the ocean will always have its dangers, hopefully, mass graveyards of shipwrecks are a thing of the past. And you know what else protects sailors is being awake when they need to be awake–with coffee.

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