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.
