What geologic process is related to caldera formation?
Calderas are formed by huge explosive volcanic eruptions. The magma chamber completely empties and the surface of the earth above it caves in forming a huge crater.
They are not necessarily important for planetary formation - directly, but they are important for the formation of solar systems and stars. When a molecular cloud exists, it will without any external intervention, stay as a molecular cloud. A supernova explosion nearby, gives the molecular cloud impetus and this starts the process of stellar evolution. [See related question] See other related questions.