Both the Spiral Jetty and Serpent Mound are examples of earthworks. The Spiral Jetty was built in April 1970 found in the Great Salt Lake. It is made of basalt rocks, mud, and salt crystals. On the other hand, the Great Serpent Mound is found in Ohio, measuring at 1,348 feet. The structure has already been tagged as a National Historic Landmark as per the US Department of Interior.
