The carvings include birds, plants, spiders, humanlike figures with headdresses, decapitated heads and an orca wielding a knife.

Described in study published Monday in the journal PNAS, the discovery almost doubles the number of known Nazca geoglyphs, mysterious artworks formed in the ground by moving stones or gravel that date back some 2,000 years. The researchers' findings also shed some light on the symbols' enigmatic purpose.

Located 50 kilometers (31 miles) inland from Peru's south coast, the huge symbols were found in the desert beginning in the early 20th century. Some 500 meters (1,640 feet) above sea level, the geoglyphs have survived the ages because the dry desert region is sparsely populated, not affected by flooding and unsuitable for growing crops.

The rate of new finds has increased in recent years due to the use of remote high-resolution imaging, with an average of 19 geoglyphs found annually from 2000 to 2020, according to the research. However, the use of AI to narrow down potential candidates has since turbocharged the pace and, more broadly, promises "a revolution in archaeological discoveries," according to the study.

A group of researchers led by Masato Sakai, a professor of archaeology at Japan's Yamagata University, pulled off the latest geoglyph discovery by training an object detection AI model with high-resolution imagery of the 430 Nazca symbols mapped as of 2020. The team included researchers from IBM's Thomas J. Watson Research Center in Yorktown Heights, New York.

Their main challenge was the limited number of images. Typically, such models are trained with the use of tens of thousands of images, according to the study.

Narrowing the Nazca field

The team chose to focus on the smaller and more figurative of the two types of symbols discovered in the desert. Figurative geoglyphs are typically around 9 meters (30 feet) in length and have been more difficult to identify than the larger line-type, which are 90 meters (98 yards) in length and thus have been more easily spotted during aerial surveys.