The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. For a summary go to water cycle.
The Gap Analysis Program (GAP) is a state-based cooperative effort to map major indicators of biodiversity over states, along with the existing network of conservation lands.
This massive database updates our knowledge of the Nation’s land cover and documents precisely where land cover change has occurred between 2001 and 2006.
The USGS provides access to water-resources data collected at approximately 1.5 million sites in all 50 States, the District of Columbia, and Puerto Rico. Online access to this data is organized around the categories listed to the left.
A rock is an aggregate of one or more minerals; or a body of undifferentiated mineral matter. 
Forest Visitor Maps are best used to view an entire National Forest. They are great for driving through or planning a trip to the forest, showing recreational sites, campgrounds, public information sites and other attractions in the forest.
Gas hydrates are found in sub-oceanic sediments in the polar regions (shallow water) and in continental slope sediments (deep water), where pressure and temperature conditions combine to make it stable. 
The U.S. Food and Drug Administration and States regulate bottled water.
For statistical information about mineral commodities, visit the USGS Commodity Statistics and Information website.