Air core drilling is a drilling technique used in geology to collect rock and soil samples from the subsurface. It involves using a drill bit with a hollow center, which allows compressed air to be pumped down through the center of the drill string and out through the bit, blowing the cuttings back up to the surface. As the air blows the cuttings to the surface, they are collected in a sample tray or bag for analysis. Air core drilling is commonly used for exploration and sampling in areas where the geology is soft or unconsolidated, such as sand, clay, or gravel, and where a traditional drill rig may not be suitable.