How flotation tanks can help archaeologists

Soils can hold a huge amount of archaeological evidence in their make-up. This includes not only the obvious flecks of charcoal or chips of flint that indicate past human activity, but also organic remains of plants and pollen grains, or even animal bones, which can help to identify the flora and fauna once dominant in the prehistoric landscape. All of this evidence can be used to help to reconstruct the environment that the people who left their footprints at Goldcliff 8,000 years ago would have known and lived in.

In order to retrieve as much material as possible, Time Team used flotation tanks. These are barrels that are pumped with a constant flow of water. A fine net is suspended just below the surface and the soil is dropped onto the netting. As the soil is broken down in the water the organic particles float to the surface and are then caught by successively smaller sieves at a run-off point to grade the evidence by size.

'This can be really useful for getting a picture of the prehistoric environment,' says Time Team's Goldcliff site supervisor Kerry Ely. 'A lot of the material we've picked up belongs to riverside reeds, but all the samples will be thoroughly checked out under a microscope and then we can really see what we've got.'

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