Calderas related to ash-flow sheets show a positive correlation between caldera area and ejecta volume; this correlation places constraints on magma drawdown during eruption and implies a systematic relationship between these parameters and magma volume of the chamber. Caldera areas range from 1 to 10⁴ km²; the volume of ejecta from caldera sites ranges from 1 to 10⁴ km³, and the volume of the related magma chambers is thought to range from 10 to 10⁵ km³.

A tentative correlation between ejecta volume and the time required to produce that volume reveals...