Land art is an art movement in which landscape and the work of art are inextricably linked. It is also an art form that is created in nature, using natural materials such as soil, rock (bed rock, boulders, stones), organic media (logs, branches, leaves), and water with introduced materials such as concrete, metal, asphalt, or mineral pigments. Sculptures are not placed in the landscape, rather, the landscape is the means of their creation. Often earth moving equipment is involved. The works frequently exist in the open, located well away from civilization, left to change and erode under natural conditions.

(from wikipedia)