A polygenetic volcanic field is a group of polygenetic volcanoes, each of which erupts repeatedly, in contrast with monogenetic volcanoes, each of which erupts only once. Polygenetic volcanic fields generally occur where there is a high-level magma chamber. These volcanic fields may show lithological discontinuities due to major changes in magma chemistry, volcanotectonic events, or long erosional intervals, and may last over 10 million years.