Robert Smithson's Spiral Jetty (1970) is an environmental artwork located in Great Salt Lake, Utah. Constructed out of mud, salt crystals, and basalt rocks in a coil formation, it examines humanity's relationship with nature and the effects of entropy. Environmental art seeks to improve connections with and understanding of the natural world through works that incorporate or are inspired by natural materials, landscapes, and ecological processes. Pioneers of the genre in the 1960s-70s included Smithson, Nancy Holt, Walter de Maria, and Andy Goldsworthy. Their site-specific works explored themes of nature and culture, permanence and impermanence. Photography is often used to document environmental artworks that change over time