 At first it was assumed that this ignimbrite crops out over a surface of but later it was found that it covers a surface closer to .Between the intracaldera ignimbrite, the parts of the ignimbrite that extend away from the caldera and outcrops at large distance, the volume is about , down from earlier estimated of volumes exceeding but the Galán eruption is still one of the biggest known volcanic eruptions.The Galán ignimbrite is the largest ignimbrite erupted by this centre; there is a tendency of the volume of individual ignimbrites to increase as the volcanoes grow younger, not only at Galán but also at other Puna ignimbrite centres, and this may be a consequence of progressive changes in the crust.