from left:

dirt from the pitcher's mound of Fenway Park
dirt and plastic grass from underneath the "Welcome to Fabulous Las Vegas" sign
dirt from the finishline at Churchill Downs, Louisville KY, home of the Kentucky Derby since 1875
sand from underneath Bleecker Street in Greenwich Village, New York City collected when a water mane burst on November 15, 2009
dirt found at Area 51 in Rachel Nevada
salt from the Great Salt Lake found at the site of Robert Smithson's Spiral Jetty, Rozel Point UT