Metamorphic rock - A rock formed by the application of heat and pressure to preexisting rocks. Plutonic rock - An igneous rock formed when magma cools and crystallizes within the earth. Volcanic rock - An igneous rock formed when molten rock called lava cools on the earth's surface. Karst - The type of geologic terrain underlain by carbonate rocks where significant solution of the rock has occurred due to flowing groundwater. Alluvium - Sediments deposited by flowing rivers.
Sediments can be different sizes depending upon the location in the floodplain of the river.
Glacial till - A glacial deposit composed of mostly unsorted sand, silt, clay, and boulders and laid down directly by the melting ice. The confining bed has a significantly lower hydraulic conductivity than the aquifer. Unconfined Aquifer - An aquifer in which there are no confining beds between the zone of saturation and the surface. There will be a water table in an unconfined aquifer. Sometimes called a water-table aquifer.