Subject
Geology
176
Geology, Stratigraphic
65
Mines and mineral resources
60
Arizona
57
Ore deposits
17
Groundwater
12
Petrology
12
Copper ores
11
Paleontology
11
Geology, Structural
9
Volcanic ash, tuff, etc
9
Wilderness areas
8
Grand Canyon (Ariz.)
7
Uranium ores
6
Water-supply
6
Geochemistry
5
Igneous rocks
5
Natural history
5
Nevada
5
Breccia pipes
4
Conservation of natural resources
4
Copper mines and mining
4
Geochemical prospecting
4
Hydrology
4
Land use Environmental aspects
4
Manganese ores
4
Sedimentation and deposition
4
Arizona Geology
3
Botany
3
Evapotranspiration
3
Forests and forestry
3
Geological mapping
3
Glen Canyon Dam (Ariz.)
3
Grand Canyon National Park (Ariz.)
3
Mineralogy
3
New Mexico
3
Plant ecology
3
Public lands
3
Riparian ecology
3
Rocks Analysis
3
Streamflow velocity
3
Subsidences (Earth movements)
3
Utah
3
Volcanoes
3
Aquifers
2
Arizona Climate
2
Cactus
2
Chinle Formation
2
Colorado River (Colo.-Mexico)
2
Desert plants
2
more ...