Subject
Geology
10
Saudi Arabia
10
Utah
4
Colorado
3
Mars (Planet)
3
United States
3
Alaska
2
Armenia (Republic)
2
Land use
2
Landforms
2
Arizona
1
Arkansas
1
California
1
Glaciers
1
Montana
1
Moon
1
Nevada
1
New York (State)
1
Saint Helens, Mount (Wash.)
1
Venezuela
1
Volcanoes
1
West Virginia
1
Wisconsin
1
Wyoming
1
Yosemite National Park (Calif.)
1