During the early prehistoric period, between approx. 700,000 and 8,000 years ago, sea level varied greatly. As a result of climatic change and a cycle of cold and warm periods, sea level rose and fell as large amounts of water were alternatively locked away in and released from ice sheets. Consequently, during various times in the Late Quaternary sea level was much lower than today and during these periods the North Sea and the English Channel became land surfaces. At times, Britain was no longer an island but became a northern peninsula of continental Europe.
During these periods this landscape became habitable to human populations. Prehistoric river valleys, or palaeovalleys, still surviving in the seabed stratigraphy are remnants of these prehistoric land surfaces. At various times during the Palaeolithic (c. 700,000-12,000 years ago), and particularly during the Upper Palaeolithic (c. 30,000-12,000 years ago) and early Mesolithic period (c. 12,000-6,000 years ago), parts of both the English Channel and the North Sea were inhabited by people.
The landscape would often have been suited to hunter-gathering-fishing communities. The pollen and fossilised micro-organisms from sediments within the seabed stratigraphy can be analysed to produce reconstructions of that environment; creating a picture of the plants, habitat, animals and the resources available to humans. This, combined with the palaeogeography (the topography of the land surface), can provide the information needed to assess the likelihood that a particular area was lived in by prehistoric communities.There are also terrace-like deposits associated with these relict, prehistoric river valley systems. The largely gravel, terrace-like deposits contain older material reworked by the ancient rivers, moved from higher up their drainage systems and redeposited in new locations. This reworked material can contain older, Lower and Middle Palaeolithic archaeological material (c. 700,000 - 30,000 years ago), primarily stone tools such as handaxes which can survive the redeposition process.
There are still a number of key research questions that need to be answered. The cycle of sea level rise and fall has created ‘layers’ of land surfaces and river valleys that overlay and cut into each other. Dating the sequence of these land surfaces so that palaeogeographies can be linked to a particular point in the early prehistoric period is an important step. Questions of how material remains were affected by being submerged, and most probably exposed and re-submerged, still remain. Equally, the effect of the sea’s movement, of waves, storms and long-term marine processes, on archaeological deposits is only beginning to be understood.
However, inshore, submerged archaeological sites in the Baltic, Scandinavia, the western Solent and Tynemouth have already been investigated. Flint tools and the bones of prehistoric animals are often dredged up by fishermen and have been found in the seabed grab-samples taken for benthic (marine life) analysis by marine biologists working on behalf of aggregate companies. Plus, the potential for preservation of organic material, such as wooden spears, axe shafts, bone harpoons, fishing equipment, skins and even dwellings, is much more likely in submerged conditions. This is exactly the kind of material that is often missing from the terrestrial archaeological record.
The study of submerged prehistoric landscapes and associated archaeological deposits is still a young science. However, the field promises to provide a different and valuable source of information about prehistoric peoples - societies in the very distant past. It has the potential to expand our knowledge of those societies and inform terrestrial archaeology, possibly even to transform the currently prevalent, terrestrial perspective itself.