The subsoil of Champagne is a superposition of layers alternating chalk, sand, and limestone marls. It is favorable to soil drainage and gives a particular minerality to certain Champagne wines. Its chalk is rich in marine microorganisms and mollusks from the Mesozoic Era (252 to 66 million years ago). Its porosity makes it a water reservoir consisting of 300 to 400 liters per cubic meter. It allows the vines to benefit from a water supply even during the driest summers.