Why is the Titanic Disappearing when some Shipwrecks Last Thousands of Years?
If you were to venture to the bottom of the Atlantic Ocean, to the Titanic's final resting place, you would find it starting to corrode at an alarming rate. In fact, it is estimated that within 20-50 years, a mere 164 years after its famous icy sinking, it will have corroded to the point of being unrecognisable.
And yet, this is not the story of every shipwreck. If you take a journey to the seafloor off the coast of Mazarrón and Playa de la Isla in Southeastern Spain, you will find a very different tale. The creatively named Mazarrón Shipwreck II met a watery end in the second half of the 7th Century BCE, over 2,500 years ago, yet most of the hull remains remarkably intact.
So, why is this? Why do some ships, like the Mazarrón II, outlive a millennium, while others, like the Titanic, are reduced to fragments and erode back to nature within just a few hundred years?
Well, it isn’t just about how old a ship is, it’s fate is determined by more factors than that. Water chemistry, oxygen levels, temperature, marine life, sediment, depth, currents, construction, and even global warming all play a part in whether a shipwreck survives or fades away.
What Happens to a Ship When It Sinks?
It is April 1912, and it has been a bad night for the Titanic, a very, very bad night, and the world-famous ocean liner has found herself at the bottom of the Atlantic.
While many ships, like the Titanic, reach the seafloor already with considerable damage from the sinking itself, even a perfectly preserved ship faces a hostile seafloor. Salt, water, currents, and marine life all start to get to work.
Two major processes drive a wreck's deterioration: chemical deterioration and biological deterioration.
Chemical deterioration occurs when seawater and dissolved oxygen trigger corrosion in metals like iron and steel, made primarily from steel; that’s bad news for the Titanic.
Biological deterioration happens when bacteria, fungi and marine organisms consume or break down materials, particularly wood, which is why even if ships like Mazarrón II have survived the millennium, the seabed around the world isn’t littered with the shipwrecks of yesteryear; the Mazarrón II, quite simply, was lucky in where and how it sank.
Once it hits the seafloor, a wreck also becomes part of its new ecosystem. Marine life doesn’t care if it is a ship or a reef; fish and other creatures can shelter around it, while microorganisms colonise its surfaces and contribute to gradual decay.
The Titanic’s twisted metal hit the ocean floor in 1912 and was immediately subject to the very first onslaught of biological and chemical deterioration.
The Mazarrón II, on the other hand, was luckier, if you can call a ship that sank 'lucky'; it sank in the shallow waters of the Mediterranean and was quickly covered in sediment and seagrass. This created a low-oxygen environment that helped shield its timber from organisms and other processes that would normally cause it to decay.
Why Does Saltwater Make Ships Corrode?
For ships made from iron or steel, seawater provides almost ideal conditions for corrosion. Salt dissolved in the water allows electrical charges to move more easily, helping create the electrochemical reactions that turn iron into corrosion products.
Three ingredients are particularly important: salt, water and oxygen.
Water enables the reactions to occur, salt increases the water's electrical conductivity, and dissolved oxygen helps drive the corrosion process. Together, these ingredients are the perfect players to create corrosion and slowly weaken exposed steel.
So, for ships like the Titanic, made primarily of metal and spending a few centuries chilling at the bottom of a salty, wet ocean, corrosion has had the time and conditions to wreak havoc.
Now, the Titanic is deep, deep underwater, so that means slightly less oxygen and colder temperatures than the surface. But, even in the deep ocean, oxygen is still present, and there is no shortage of salty water, which means that the lower oxygen levels and lower temperatures simply weren’t enough to save the Titanic.
Why Is Titanic's Wreck Slowly Disappearing?
The Titanic is not simply resting intact on the seabed. Since it sank in 1912, sections of the hull and superstructure have deteriorated, while microorganisms have colonized the exposed metal.
Some of these microorganisms form rusticles. These are structures that, as the name suggests, look like icicles made of rust, and much like icicles hang from a porch in the winter, rusticles hang from the wreck. But where an icicle may be made of only ice, a rustilce is a little trickier than just being made from rust. Rusticles instead are entire microbial communities. These microbial neighbourhoods consume iron and contribute to the wreck's deterioration. These rusticles are effectively eating the iron of the Titanic.
Can Mud and Sand Protect a Shipwreck?
Unlike the exposed parts of the Titanic, part of what the Mazarrón owes its longevity to is the fact that it is covered in sediment. If you are a shipwreck, being buried in the ocean is a good thing for survival. Mud and sand burying a vessel limit its contact with moving, oxygenated water and marine organisms. As a result, buried material can often survive considerably longer than exposed sections.
Mud and sand can also help to protect against currents. The Titanic is an area exposed to the western boundary current. This current is strong, changeable and constant, it stops sediment from building up against the hull of the Titanic, brings new organisms and corrosive materials to the Titanic site, and the current itself quite literally wears away and causes holes in what remains of the ship.
Why Doesn't the Wooden Part of a Shipwreck Just Rot Away?
Wood faces a different set of threats underwater than its metal counterparts. Bacteria, fungi and marine organisms gradually break down timber, with the rate depending heavily on the surrounding environment. The shipworm is one organism that is particularly destructive. This pesky marine mollusk burrows into and consumes submerged wood.
For wood vessels, warmer waters can actually prove more problematic than colder ones, which means again, the Mazarrón II was lucky that it got covered with sediment. Warm water is often more biologically active than freezing water, which means things like shipworm are more active and more destructive.
However, this doesn’t mean that ships in the icy deep are safe; the rate of decay just may be slightly slower than exposed wood in warmer waters. Among the ecosystem of the Titanic are bacteria found nowhere else in the world, and the wooden decks of the ship have already been lost to nature.
Why Do Some Metals Survive Better Than Others?
Not all metals behave the same way underwater. Iron and steel corrode easily, while metals such as copper and some of its alloys can be considerably more resistant under certain conditions. The exact composition of an alloy, its surface and the surrounding water all affect how quickly it deteriorates.
Using different metals together can also create additional corrosion problems because they can participate in electrochemical reactions with one another; unfortunately for many wrecks, using multiple types of materials is common in shipbuilding. The Titanic, for example, has steel, iron, copper, just to name a few, and these metals not only deteriorate at different rates, but also can help each other to deteriorate too.
Does a Ship's Location Determine How Long It Survives?
Temperature affects chemical reactions and biological activity; salinity influences the chemistry of water and corrosion rates; oxygen contributes to chemical corrosion and biological processes. Meanwhile, currents expose surfaces and move sediments, marine organisms colonize, consume or chemically alter wreck materials, and depth changes pressure, temperature, light and the surrounding ecosystem. Where a wreck has come to rest will change its chances of surviving the centuries.
A shipwreck isn't just sitting in the ocean. It is sitting in a particular chemical, biological and physical environment, and that environment is part of what makes a wreck last or be erased by the elements.
What Can Titanic Teach Us About Shipwreck Preservation?
The Titanic was an incredible tragedy, but out of that tragedy an underwater scientific laboratory has emerged, offering researchers a rare opportunity to observe the long-term deterioration of a large steel ship in the deep ocean. Remotely operated vehicles have mapped the wreck, and its changing condition has been studied; microbial ecosystems, the impact of currents, depth, and pressure and the formation of rusticles have all been examined to give insights into how materials react, behave, and survive or perish in the deep.
This information goes beyond just shipwrecks; it gives insights into materials that can be used for underwater infrastructure and how long-term exposure to this environment impacts structures.
But the wreck is only half of Titanic's story. The other half begins in Belfast.
Visiting Belfast and The Home of the Titanic
The Titanic is more than just a shipwreck; it is a tale of tragedy, adventure, perseverance, and over 2200 lives in the middle of the Atlantic Ocean. Visitors to Belfast can explore the city where the ship was designed, built and launched, and see the places that connect the modern city to one of the most famous ships in history.
Titanic Belfast and a Let’s Walk Belfast tour offer an opportunity to learn about the Titanic’s construction and the people who built her, while the surrounding Titanic Quarter preserves much of the industrial landscape that made Belfast one of the world’s great shipbuilding centres.
Seeing the Titanic’s origins in Belfast alongside its gradual disappearance on the floor of the North Atlantic adds another dimension to the tale. The ship may be slowly returning to nature, but its connection to the city that built it remains very much alive.
Every Shipwreck Has Its Own Tale
The Titanic and the Mazarrón Shipwreck II show us that a shipwreck's survival is not simply a matter of age. The environment around a wreck can determine whether it survives for centuries or slowly disappears in just a few generations. For the Titanic, saltwater, oxygen, microorganisms, currents and time are gradually breaking down the steel that once made it one of the greatest ships ever built.
Yet, as the wreck disappears beneath the waves, its story continues above them. From the seabed of the North Atlantic to the shipyards of Belfast, the Titanic remains a reminder that while ships may eventually return to nature, the stories we attach to them can last for thousands of years.
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