hafnium (100) city halls -> buildings (9) halls -> buildings (9) town halls -> buildings (9) halting places (transportation) -> transportation features (1) hammocks -> physiographic features (401) hand-held field spectroscopy -> handheld field spectroscopy (2) handheld field spectroscopy (2) harbors (1) harbours -> harbors (1) water hardness (1) hardness (water) -> water hardness (1) seismic hazard maps (2) -> earthquake occurrences -> maps and atlases hazard preparedness (1) earthquake hazards (1) -> earthquakes -> hazards environmental hazards -> hazards (3) geologic hazards -> hazards (3) hazards (3) mining hazards (2) headquarters -> buildings (9) park headquarters -> buildings (9) headwaters -> drainage basins (1) human health -> environmental health (human) (5) environmental health (human) (5) health (human) -> environmental health (human) (5) health and disease (6) slag heaps -> disposal sites (7) heat flow (earth) (2) heatflow (earth) -> heat flow (earth) (2) gage height -> streamflow (2) helium (10) high-pressure liquid chromatography -> liquid chromatography (1) highway maintenance sites -> transportation features (1) highways -> roadways (1) hills -> mountains (1) earth history (2) geologic history (34) life history -> population and community ecology (2) strain history -> deformation (geologic) (13) holes (seafloor) -> seafloor features (1) holmium (114) A horizon -> soil horizons (2) B horizon -> soil horizons (2) C horizon -> soil horizons (2) soil horizons (2) hostels -> buildings (9) hotels -> buildings (9) hot springs -> thermal features (1) club houses -> buildings (9) community houses -> buildings (9) customs houses -> buildings (9) houses -> buildings (9) human disease -> environmental health (human) (5) human environmental safety (3) human health -> environmental health (human) (5) human impacts (53) hunting reserves -> reserves (1) hydraulic fracturing (1) hydroelectric power stations -> power generation sites (1) hydrofracking -> hydraulic fracturing (1) hydrogen (5) hydrogeology (28) hydrographic features (18) hydrographic sections -> hydrogeology (28) hydrographic structures (2) hydrologic processes (17) hydrology (2) hydrosphere -> water resources (32) hydrothermal processes (4) hyperspectral imaging (8) hyporheic zone processes -> groundwater and surface-water interaction (7) hypoxia -> oxygen content (water) (10)