marine and underwater archaeology
Humankind's artefacts litter the seabed, partly as a result of mercantile and naval activities, but also because landscapes have become submerged. This submergence is not only the result of the sea level rising as the ice caps melted at the end of last glaciation 20,000 years ago, but also a result of tectonic movements. For example, the southern half of the North Sea was only inundated by the sea about 7,000 years ago. Up until then it had been sparsely populated by bands of stone age hunter-gatherers and in 2003 two stone-age settlements dating back to the Mesolithic period, between 10,000 and 5,000 years ago, were found off the coast of Tyneside. The seashore always offered a rich abundance of resources for these early peoples. In historical times tribes of North American indigenous peoples such as the Haida of the Vancouver region had lifestyles intimately adapted to life on the coast. On islands in the Caribbean the refuse tips or middens left by the Caribs, when excavated, have shown how the diets of these coastal peoples changed, partly because of climate change, but also because of their impact on the resources they were exploiting. Sea levels also change locally because of tectonic movements. These can be slow, gradual shifts: for example in south-east Britain the land is sinking about 1 mm per year, fast enough to turn several coastal archaeological sites into marine sites over the centuries. However, in many places siltation has meant that harbours used in Roman and medieval times are now some distance from the sea. In the Mediterranean the impact of the African tectonic plate pushing up against the Eurasian plate has been rotating the island of Crete so that Graeco-Roman harbours are now high and dry above sea level on one side of the island but submerged on the other.
Some tectonic movements are sudden and violent. On Christmas Day 1968 a strong earthquake near Anchorage in Alaska resulted in vertical shifts of some parts of the coast by over a metre, and Charles Darwin was greatly influenced by witnessing the impact of a metre shift in sea level near Santiago in Chile. But perhaps the most significant archaeological event was the explosive end of the island of Santorini in the Mediterranean that brought the Minoan civilization centred on Crete to an abrupt end. Such events add to the archaeological record not only by dropping local sea levels but also through the destructive power of the tsunamis they generate, which wash immense numbers of artefacts into the sea.
Perhaps one of the most remarkable prehistorical underwater sites is the Cosquer Cave near Marseille, which is at the end of a 175-metre- (575-ft)-long tunnel 37 metres (120 ft) below sea level. The cave is not accessible to the general public, but it is now possible to make a virtual visit to see the remarkable paintings of horse, ibex, aurochs, jellyfish, great auks, and human hands, which were probably painted during the last glaciation when the sea was 70 metres (230 ft) lower than today.