Traditionally an archive is a store of documents or artefacts of a purely documentary nature. The rise of performance art in the twentieth century meant that artists became heavily reliant on documentation as a record of their work. A similar problem arose in relation to the Land art movement of the 1960s whose interventions in the landscape were often eradicated by the elements. Conceptual art often consisted of documentation. In practice the documentation—photograph, video, map, text—was rapidly adapted to have the status of artwork. Some artists have used the actual structure of the archive for their work. In 1999 Mark Dion sifted the silt beds of the Thames and displayed the contents in mahogany cabinets at Tate Britain, London. Over six years Jeremy Deller, together with Alan Kane, collated his epic Folk Archive, which documents popular culture around the United Kingdom and Ireland.