Following the small terrestrial and submarine volcanoes discussed in the previous chapter, we now turn to polygenetic volcanoes. These have in common a complex plumbing system with a number of conduits, and produce a range of eruptive products, often with various lithologies (Cas and Wright in Volcanic successions: modern and ancient. Springer, Dordrecht, Netherlands, 1988), and build up over tens to hundreds of kyr up to a few Myr. The two main groups of polygenetic volcanoes are shield volcanoes and strato- or composite volcanoes.