The Galán ignimbrite is fairly homogeneous and has a high crystal content; overall it appears that the eruption commenced and reached large dimensions fairly quickly without leaving time for an eruption column or distinct flow units to form, except in some places. Conversely, the produced flows were relatively slow flows that had little capacity to pass above topographic obstacles or to move rocks around. It nevertheless spread over large distances, since the topography of the region had been flattened by the previous Toconquis ignimbrites, and was still hot by the time it came to a standstill. Pumice is scarce and usually present in only small fragments, and lithic fragments are also uncommon except at the bases of the deposit. Fiamme structures on the other hand are fairly common especially where the ignimbrite crossed river valleys. The ignimbrite displays varying degrees of welding but has often spectacular columnar joints.