Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.The United States Geological Survey (USGS) is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility. A bureau of the United States Department of the Interior, it is that department''s sole scientific agency. The USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices in Lakewood, Colorado (Denver Federal Center), and Menlo Park, California.