Over Earth’s 4.5 billion-year history, tectonic upheavals and colliding plates formed mountain ranges and carved out basins. Forces of erosion and weathering have been at work to break down these landforms. Records of these processes are imprinted on the land and define distinctive landscapes around the United States and in its national parks.
Archaeological remains include artifacts (portable) and features (non-portable) made and used by humans. Archaeologists use these objects to understand how ancient people lived. How well archaeological remains survive depends on the materials they were made of, the ways they were used, the manner in which they were discarded, and the environment in which they were deposited. Organic remains generally decay in a short time unless preserved in special conditions.