Earthworks, also known as land art, are works of art made of natural materials such as earth, rocks, water—usually on an extremely large scale. Land art became popular in the 1960s. Earthworks have been linked to minimalism due to their inherent simplicity and some scholars have called this form a reaction against consumerism because it is nearly impossible for anyone to buy or sell (or exhibit) land art. The most famous example of an earthwork is Spiral Jetty, built on Rozel Point in the Great Salt Lake in Utah in 1970 by artist Robert Smithson. Spiral Jetty is monumental indeed—a 1,500 foot long embankment made of earth, mud, and basalt rocks that juts into the lake. Periodically submerged due to the changing levels of the lake, earthworks such as Spiral Jetty are built on such a large scale that they evoke the mystery and largess of ancient monuments and sites such as Cahokia or Serpent Mound. Other examples of earthworks are Michael Heizer’s Double Negative (1969—70), which was created by cutting the sides of a canyon wall in the Arizona desert, as well as Walter de Maria’s Lightning Field (1977).