The ancient, intricate geometric patterns stamped on the surface of a desert in Peru have long been thought of as messages to the gods, or as markers that tracked celestial objects. Now new details about these geoglyphs suggest they may have been made for "prayer walking".The Nasca lines are a collection of lines, giant trapezoids, and figures of humans, plants and animals in a desert 400 kilometres south of Lima, Peru. They were created between 400 BC and AD 650 by the removal of reddish oxidisedstones from the desert pavement to reveal the lighter sand beneath.Tomasz Gorka of Munich University in Germany analysed five geoglyph complexes near the city of Palpa, focusing on the large trapezoidal structures which are etched on the plains there.
He measured anomalies in the Earth's magnetic field caused by changes in soil density at various depths. The team walked the entire site, an area of about 60 hectares, using hand-held sensors. "We found other lines, in the interior of the trapezoid structures, which were not visible from the air," says Gorka, who presented his findings at an archaeological geophysics meeting in London last month. "The geoglyphs visible today are the most recentstage of a prolonged construction process during which the whole complex of drawings was constantly added to, remodelled, obliterated or changed by use," adds Gorka. Some of the lines produced stronger magnetic anomalies than others, prompting Gorka and Karsten Lambers of the University of Konstanz in Germany to suggest that the soil beneath was compacted by people walking back and forth during prayer rituals. "This activity was closely connected to the placing of ceramic vessels along the lines," perhaps as offerings, says Lambers.