Maritime archaeology

An example from the prehistoric era would be the remains of submerged settlements or deposits now lying under water despite having been dry land when sea levels were lower.

[6] Maritime archaeological sites often result from shipwrecks or sometimes seismic activity, and thus represent a moment in time rather than a slow deposition of material accumulated over a period of years, as is the case with port-related structures (such as piers, wharves, docks and jetties) where objects are lost or thrown off structures over extended periods of time.

A feature of maritime archaeology is that despite all the material that is lost, there are occasional rare examples of substantial survival, from which a great deal can be learned, due to the difficulties often experienced in accessing the sites.

As a result, marine channels, navigable rivers and sea crossings formed the trade routes of historic and ancient civilisations.

Later, nations with a strong maritime culture such as the United Kingdom, the Netherlands, Denmark, Portugal and Spain were able to establish colonies on other continents.

Of late maritime archaeologists have been examining the submerged cultural remains of China, India, Korea and other Asian nations.

There are significant differences in the survival of archaeological material depending on whether a site is wet or dry, on the nature of the chemical environment, on the presence of biological organisms and on the dynamic forces present.

[8] Survival in this instance is largely due to the remains being buried in sediment Of the many examples where the sea bed provides an extremely hostile environment for submerged evidence of history, one of the most notable, RMS Titanic, though a relatively young wreck and in deep water so calcium-starved that concretion does not occur, appears strong and relatively intact, though indications are that it has already incurred irreversible degradation of her steel and iron hull.

As such degradation inevitably continues, data will be forever lost, objects' context will be destroyed and the bulk of the wreck will over centuries completely deteriorate on the floor of the Atlantic Ocean.

USS Monitor, having been found in the 1970s, was subjected to a program of attempted in situ preservation,[10] for example, but deterioration of the vessel progressed at such a rate that the rescue of her turret was undertaken lest nothing be saved from the wreck.

The shipwreck lay forgotten at the bottom of the sea until it was discovered in 2002 by an oilfield inspection crew working for the Okeanos Gas Gathering Company (OGGC).

[12] Large pipelines can crush sites and render some of their remnants inaccessible as pipe is dropped from the ocean surface to the substrate thousands of feet below.

The wrecks, and other archaeological sites that have been preserved have generally survived because the dynamic nature of the sea bed can result in artifacts becoming rapidly buried in sediments.

Wet environments, whether on land in the form of peat bogs and wells, or underwater are particularly important for the survival of organic material, such as wood, leather, fabric and horn.

While the land surface is continuously reused by societies, the sea bed was largely inaccessible until the advent of submarines, scuba equipment and remotely operated underwater vehicles (ROVs) in the twentieth century.

The engine of SS Xantho that was recovered in 1985 from a saline environment after over a century underwater is presently considered somewhat anomalous, in that after two decades of treatment it can now be turned over by hand.

A site that has been discovered has typically been subjected to disturbance of the very factors that caused its survival in the first place, for example, when a covering of sediment has been removed by storms or the action of man.

Active monitoring and deliberate protection may mitigate further rapid destruction making in situ preservation an option, but long-term survival can never be guaranteed.

Unlike the wrecking of a ship, the destruction of a town by a seismic event can take place over many years and there may be evidence for several phases of damage, sometimes with rebuilding in between.

The first known use of the method comes from 1446, when Leon Battista Alberti explored and attempted to lift the ships of Emperor Caligula in Lake Nemi, Italy.

In the 19th century, the standard copper helmet diving gear was developed, allowing divers to stay underwater for extended periods through a constant air supply pumped down from the surface through a hose.

Nevertheless, the widespread utilisation of diving gear for archaeological purposes had to wait until the 20th century, when archaeologists began to appreciate the wealth of material that could be found under the water.

The third tier consists of the archaeology of maritime cultures, in which nautical technology, naval warfare, trade and shipboard societies are studied.

Notable early Iron Age shipwrecks include two Phoenician ships of c. 750 BC that foundered off Gaza with cargoes of wine in amphoras.

Though sailing was the safest, fastest, and most efficient method of transportation in the ancient world, some fractional percentage of voyages ended in shipwreck.

Discovered in 1900 by Greek sponge divers, the ship probably sank in the 1st century BC and may have been dispatched by the Roman general, Sulla, to carry booty back to Rome.

In the same area, the submerged town of Puteoli (Pozzuoli, close to Naples) contains the "portus Julius" created by Marcus Vipsanius Agrippa in 37 BC, later sunk due to bradyseism.

Other finds are consistent with some passages of the Bible (like the so-called Jesus boat,[clarification needed] which appears to have been in use during the first century AD).

Maritime archaeology in Australia commenced in the 1970s with the advent of Jeremy Green due to concerns expressed by academics and politicians with the rampant destruction of the Dutch and British East India ships lost on the west coast.