Discovering ancient settlements is often rather hit and miss, but the odds would be improved with a bit of chemical analysis. Plants growing over old sites of human habitation have a different chemistry from their neighbours, and these differences can reveal the location buried ruins.
Plants mostly take in nitrogen from the soil as the isotope nitrogen-14, with just a dash of nitrogen-15. Plants growing above archaeological sites in Greenland, however, seem to have absorbed a larger dose of nitrogen-15.
Rob Commisso and Erle Nelson from Simon Fraser University in British Columbia, Canada, spent three summers collecting plants from sites in south-west Greenland. Some of their samples were unusually rich in nitrogen-15, and subsequent digs revealed that these plants had been growing above long-abandoned Norse farmsteads (Journal of Archaeological Science, vol 33, p 1167).
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Human habitation and farming can explain the enrichment. 鈥淔or archaeological sites the nitrogen is derived from refuse or other nitrogenous compounds that people have deposited in the past,鈥� says Commisso. This will contain more nitrogen-15 than uncultivated soil.
