Region
Nevada
93
Alaska
62
California
57
Colorado
54
Idaho
36
United States
32
Arizona
19
New Mexico
19
Nye County
19
Montana
18
Humboldt County
17
Missouri
17
Utah
15
Lander County
14
Wyoming
12
Esmeralda County
11
North Carolina
10
Earth (Planet)
9
Texas
9
Saudi Arabia
8
South Carolina
8
Washington (State)
8
Long Valley (Mono County)
7
West Chichagof-Yakobi Wilderness
7
China
6
Jefferson County
6
Marshall Islands
6
Minnesota
6
Monterey Formation (Calif.)
6
Oklahoma
6
Phosphoria Formation
6
Russia (Federation)
6
Wisconsin
6
Yellowstone National Park
6
New York (State)
5
Piceance Creek Watershed
5
San Bernardino County
5
South Dakota
5
Arkansas
4
Cabarrus County
4
Edwards Aquifer (Tex.)
4
Florida
4
Hawaii
4
Idaho National Laboratory Region
4
Kansas
4
Maine
4
Middle West
4
Oregon
4
Puerto Rico
4
Santa Maria Basin
4
more ...