The rock carvings on the Pyramid Lake Indian Reservation in Nevada are fairly well known, but no one knew just how old they were before paleoclimatologist Larry Benson dated them using the history of the area's climate.
"They're almost unique in the sense that the grooves have been carved down almost an inch deep in some cases," says Benson, an emeritus scientist with the U.S. Geological Survey who does research for the University of Colorado and its Museum of Natural History.
Just by looking at the designs, Benson thought he might know how old they were. He noticed that the symbols are much whiter than the gray rock they're carved into.
He knew from his climate research that the dry area where the petroglyphs are located was once a lake, and that the white coating was probably left from the last time the rocks were submerged in water, which suggested that the petroglyphs may be older than 11,000 years
"And I did know, at least from my limited knowledge, that these were probably older than the oldest dated petroglyphs in North America," he recalls.
By comparing the coatings of the carved rocks with non-carved rocks in the area, he determined that the petroglyphs were carved in a dry period between 10,000 and 14,800 years ago. Read more about the dating process at NPR. Link -via Metafilter
(Image credit: Larry Benson)