Shipwreck

From Wikipedia, the free encyclopedia

This article is about the remains of a wrecked ship. For the SS-N-19 Shipwreck anti-ship missile, see P-700 Granit. For the G.I. Joe character, see Shipwreck (G.I. Joe).

Shipwreck of the SS American Star

Shipwreck in the Saugatuck River mouth in Westport, Connecticut

A shipwreck or sunken ship can refer to the remains of a wrecked ship or to the event that caused the wreck, such as the striking of something that causes the ship to sink, the stranding of the ship on rocks, land or shoal, or the destruction of the ship at sea by violent weather.

1 Types of shipwrecks
2 Shipwrecks and the law
3 Salvage of wrecks
4 Causes
5 State of preservation
6 See also
7 References
8 External links

[edit] Types of shipwrecks

Historic shipwrecks are attractive to maritime archaeologists because they preserve historical information; for example, studying the wreck of Mary Rose revealed information about seafaring, warfare and life in the 1500s. Military wrecks that were caused by a skirmish at sea are studied to find details about the historic event and reveal much about the battle that occurred. Discoveries of treasure ships, often from the period of European colonisation, which sunk in remote places, leaving few living witnesses, such as the Batavia, do occur but only very infrequently.

Some contemporary wrecks, such as the Prestige or Erica, are of interest primarily because of the potential harm to the environment. Other contemporary wrecks are scuttled in order to spur reef growth, such as Adolphus Busch and the Ocean Freeze. Wrecks like Adolphus Busch and many historic wrecks such as SS Thistlegorm are of interest to recreational divers who enjoy diving shipwrecks because they are often interesting to explore, provide large habitats for many types of marine life and have an interesting history.

A very few shipwrecks are famous catastrophes like the wrecks of the Titanic or Estonia. There are also thousands of wrecks that were not lost at sea but have been abandoned or sunk. These are typically smaller vessels such as fishing vessels. These vessels can provide an interesting recreational dive but are usually of little interest to historians. They may pose a hazard to navigation and may be removed by Port Authorities. These vessels are sometimes referred to as abandoned or derelicts.

[edit] Shipwrecks and the law

Shipwreck law determines important legal questions regarding wrecks, perhaps the most important question being the question of ownership.

MSC Napoli beached off Branscombe

The British Protection of Wrecks Act, enacted to protect historic wrecks, controls access to wrecks such as Cattewater Wreck which can only be visited or investigated under licence. The British Protection of Military Remains Act 1986 also restricts access to wrecks which are sensitive as war graves. The Protection of Military Remains Act in some cases creates a blanket ban on all diving, for others divers may visit provided they do not touch, interfere with or penetrate the wreck. In the United States waters shipwrecks in state waters are regulated by the Abandoned Shipwreck Act of 1987. This act is much more lenient in allowing more open access to the shipwrecks.

Following the beaching of the MSC Napoli, as a result of severe damage incurred during European windstorm Kyrill, there was confusion in the press and by the authorities about whether people could be prevented from helping themselves to the flotsam which was washed up on the beaches at Branscombe. Many people took advantage of the confusion and helped themselves to the cargo. This included many BMW motorbikes[1] and empty wine casks as well as bags of disposable nappies. The legal position under the Merchant Shipping Act 1995 is that any such finds and recovery must be reported within 28 days to the Receiver of Wreck [2]. Failure to do so is an offence under the Merchant Shipping Act and can result in a criminal record for theft by finding[3]. After several days, the police and Receiver of Wreck, in conjunction with the landowner and the contracted salvors established a cordon to prevent access to the beach[4]. A similar situation occurred after the wreck of the MV Cita in 1997.

A very important international Convention aiming at the protection of underwater cultural heritage (including wrecks) is the UNESCO 2001 Convention on the Protection of the Underwater Cultural Heritage.

[edit] Salvage of wrecks

Often, attempts are made to salvage recently wrecked ships to recover the whole or part of the ship, its cargo, or its equipment. A good example of this was the salvage of the Kaiserliche Marine High Seas Fleet at Scapa Flow in the 1920s. The unauthorized salvage of wrecks is called wrecking.

As a general rule, civilian shipwrecks are considered fair game for salvage; military wrecks, however, remain under the jurisdiction--and hence, protection--of the government that lost the ship, or that government's successor. Hence, a German U-boat from World War II still technically belongs to the German government, even though the Third Reich is long-defunct.

Older wrecks are often protected from pillaging and looting through national laws protecting cultural heritage. Internationally they may be protected by a State ratifying the Unesco Convention on the Protection of the Underwater Cultural Heritage. In this case pillaging is not allowed.

Shipwreck , by Claude Joseph Vernet.

[edit] Causes

Ships are lost for many reasons, including:

poor design or failure of the ship's equipment
instability, due to poor design, improperly stowed cargo, or cargo that shifts its position
navigation errors and other human errors, leading to collisions or running aground
bad weather
warfare, piracy, mutiny, or sabotage including: guns, fire, torpedoes, depth charges, mines and bombs.
fire
intentional sinking (scuttling)
- to form an artificial reef
- during scheduled target practice or in testing a new weapon
- to create an obstacle to close a harbor, river, etc against enemy ships
- to prevent a ship from falling into an enemy's hands
- to destroy a derelict ship that poses a menace to navigation
- as part of an insurance scam

[edit] Equipment failure

Failure or leaking of the hull is a serious problem that can lead to the loss of buoyancy and the sinking of the vessel. Even the hulls of large modern ships have cracked in heavy storms. Leaks between the hull planks of wooden vessels is a particular problem.

Failure of the means of propulsion, such as engines, sails or rigging, can lead to the loss of a ship. When the ship's movement is determined only by currents or the wind and particularly by storms, a common result is that the ship is unable to avoid natural hazards like rocks, shallow water or tidal races.

[edit] Instability

Instability is caused by the center of mass or other forces acting on the ship rising above the center of buoyancy resulting in the ship tipping on its side or capsizing.

This can lead to a sinking if the openings on the upper side of the side are not watertight at the time of the capsize. To remain buoyant, the hull of a vessel must prevent water entering the large air spaces of the vessel. Clearly for the ship to float, the submerged parts of the hull will be waterlogged, but the upper parts of the hull must have openings to allow the crew to work and to load and unload cargo.

[edit] Bad weather

Poor weather can cause several problems:

wind
low visibility
cold

Wind causes waves which result in other difficulties. Waves make navigation difficult and dangerous near shallow water. Also, waves create buoyancy stresses on the structure of a hull. The weight of breaking waves on the fabric of the ship force the crew to reduce speed or even travel in the same direction as the waves to prevent damage. Also, wind stresses the rigging of sailing ships.

The force of the wind pushes ships in the direction of the wind. Vessels with large windage suffer most. Although powered ships are able to resist the force of the wind, sailing vessels have few defences against strong wind. When strong winds are imminent, sailing vessels typically have several choices:

try to position themselves so that they cannot be blown into danger
shelter in a harbour
anchor behind a sheltering landform

Many losses of sailing ships were caused by sailing, with a following wind, so far into a bay that the ship became trapped upwind of a lee shore, being unable to sail into the wind to leave the bay.

Low visibility caused by fog, mist and heavy rain increase the navigator's problems.

Cold can cause metal to become brittle and fail more easily. A build-up of ice high on the ship can cause instability.

[edit] Fire

Fire can cause the loss of ships in many ways. The most obvious way would be the loss of a wooden ship which is burned until watertight integrity is compromised. The detonation of cargo or ammunition can cause the breach of a steel hull. Often a large fire causes a ship to be abandoned and left to drift. Should it run aground beyond economic salvage, it becomes a wreck. In certain cases, the use of seawater to extinguish a fire results in loss of buoyancy, as was the case for the liner SS Normandie.

[edit] Navigation errors

Many shipwrecks have occurred when the crew of the ship allowed the ship to collide with rocks, reefs, icebergs, or other ships. Accurate navigation is made more difficult by poor visibility in bad weather. Also, many losses happened before modern navigation aids such as GPS, radar and sonar were available. Until the twentieth century, the most sophisticated navigational tools and techniques available - dead reckoning using the magnetic compass, chronometer and sextant - were rather inaccurate.

Even today, when highly accurate navigational equipment is readily available and universally used, there is still scope for error. Using the incorrect horizontal datum for the chart of an area may mislead the navigator, especially as many charts have not been updated to use modern data. It is also important for the navigator to appreciate that charts may be significantly in error, especially on less frequented coasts. For example, a recent revision of the map of South Georgia in the South Atlantic showed that previous maps were in some places in error by several kilometres.

Over the centuries, many technological and organisational developments have been used to reduce accidents at sea including:

pilotage aids including lighthouses and sea marks
basic navigation tools such as the magnetic compass, nautical chart, chronometer, sextant, log
advanced navigation tools such as the radio communication, gyrocompass, sonar, hyperbolic radio navigation and satellite navigation
inspection of shipbuilding quality and maintenance of seaworthiness of the ship such as "A1 at Lloyd's"
better defences to protect the ship from acts of violence, war and piracy
use of fireproof/unflamable materials to prevent fires from spreading rapildly
built-in devices to delay flooding long enough for rescue ships to retrieve survivors and/or tow the ship to the nearest shipyard for repairs, such as watertight compartments and pumps.

[edit] State of preservation

Many factors determine the state of preservation of a wreck:

the ship's construction materials
the salinity of the water the wreck is in
the level of destruction involved in the ship's loss
whether the components or cargo of the wreck were salvaged
whether the wreck was demolished to clear a navigable channel
the depth of water at the wreck site
the strength of tidal currents at the wreck site
the exposure to surface weather conditions at the wreck site
the presence of marine animals that consume the ship's fabric
temperature

[edit] Construction materials

Exposed wooden components decay quickly. Often the only wooden parts of ships that remain after a century are those that were buried in silt or sand soon after the sinking. An example of this is the Mary Rose.

Steel and iron, depending on their thickness, may retain the ship's structure for decades. As corrosion takes place, sometimes helped by tides and weather, the structure collapses. Thick ferrous objects like cannons, steam boilers or the pressure vessel of a submarine often survive well underwater in spite of corrosion.

Propellers, condensers, hinges and port holes were often made from non-ferrous metals such as brass and phosphor bronze, which do not corrode easily.

[edit] Salinity of water

Shipwrecks typically decay rapidly when in sea water; however shipwrecks in some fresh water lakes, such as the Great Lakes of North America, have remained intact with little degradation. There are two reasons for this. Iron-based metals corrode much more quickly in sea water due to the dissolved salt present; the sodium and chloride ions chemically accelerate the process of metal oxidation which, in the case of ferrous metals, leads to rust. Bacteria found in sea water cause the wood on ships to rot more quickly than in fresh water. In some sea areas, most notably in Gulf of Bothnia and Gulf of Finland, salinity is very low, and centuries-old wrecks have been preserved in reasonable condition.

[edit] Loss, salvage and demolition

An important factor in the condition of the wreck is the level of destruction at the time of the loss or shortly afterwards due to the nature of the loss, salvage or later demolition.

Examples of severe destruction at the time of loss are:

being blown onto a beach, reef or rocks during a storm
collision with another ship
destruction in warfare

After the loss the owners of the ship may attempt to recover valuable parts of the ship or its cargo. This can cause damage.

Shipwrecks in shallow water near busy shipping lanes are often demolished to reduce the danger to other vessels.

[edit] Depth, tide and weather

Wrecks are slowly broken up by exposure to breaking waves, the weather and the tides. Additionally, wrecks in deeper water suffer more degradation due to higher levels of water pressure.

[edit] Temperature

Extreme cold (such as in a glacial-fed lake) can slow degradation of organic ship materials.

[edit] See also

[edit] References

Hans Blumenberg, Shipwreck with Spectator: Paradigm of a Metaphor for Existence (Cambridge, Mass.: MIT Press, 1997)

[edit] External links

Wikimedia Commons has media related to:

Shipwrecks

Retrieved from "http://en.wikipedia.org../../../s/h/i/Shipwreck.html"

Category: Shipwrecks