Groundwater originates from water that infiltrates through soil and rock below the earth's surface. It is found in aquifers, which are saturated geological formations that are capable of providing usable quantities of water. The main sources of groundwater are meteoric water from rainfall and snowmelt, connate water trapped in sediments when they were deposited, and magmatic water from volcanic activity. Groundwater composition varies depending on the geology, but common dissolved ions include bicarbonates, carbonates, chlorides, sulfates, fluorides, calcium, magnesium, sodium, and manganese.