The Museum of Contemporary Art (MOCA) is currently holding an exhibition on Land art, "capturing the simultaneous impulse emergent in the 1960s to use the earth as an artistic medium and to locate works in remote sites far from familiar art contexts". The exhibition runs until September 3rd.
Even if you can't get to MOCA to view the exhibition then you can still view an accompanying interactive application that maps key artworks in the exhibition. Ends of the Earth: Land Art to 1974 uses Google Maps and Google Street View to pinpoint the original locations of the featured artworks.
For each artwork it is possible to view a satellite image, or a Street View image where available, of the artwork's location. It is also possible to view a photograph of the work of art in situ overlaid on top of the Google Map or Street View.