Look: Drought in Brazil's Amazon reveals ancient engravings

An extreme drought in parts of the Amazon has led to a dramatic drop in river water levels, exposing dozens of usually submerged rock formations with carvings of human forms that may date back some 2,000 years.

The rock carvings are not usually visible because they are covered by the waters of the Negro River, whose flow recorded its lowest level in 121 years last week.

The surfacing of the engravings on the riverbank have delighted scientists and the general public alike but also raised unsettling questions.

The engravings comprise an archaeological site of "great relevance," said Jaime Oliveira of the Brazilian Institute of Historical Heritage (Iphan).

They are at a site known as Praia das Lajes and were first seen in 2010, during another period of drought not as severe as the current one.

Most of the engravings are of human faces, some of them rectangular and others oval, with smiles or grim expressions.

Archaeologist Jaime Oliveira shows ancient rock engravings that reappeared in the region of the Lajes Archaeological Site due to the severe drought affecting the region's rivers on the banks of the Negro River in Manaus, Amazonas State.

Archaeologist Jaime Oliveira shows ancient rock engravings.

Ancient rock carvings that reappeared in the region of the Lajes Archaeological Site.

Ancient rock carvings that reappeared in the region of the Lajes Archaeological Site due to the severe drought