is one single flow. The upper Lower Purico Ignimbrite is more heterogeneous, starting with a base surge, a pumice layer and then another flow unit, which is volumetrically the largest part. The Lower Purico Ignimbrite covers a surface of primarily on the western side of the Purico complex. Finally, the Upper Purico Ignimbrite is a moderately to densely welded flow that occurs particularly close to the summit of the Purico complex, where it forms six flow units that contain fiamme textures. Characteristic for the Purico ignimbrite is the so-called "banded" pumice, which consist of alternating darker mafic and brighter components, in the upper 33% of the ignimbrite. The extrusion of the Purico ignimbrite was accompanied by the eruption of large amounts of tephra, some of which fell as far as the Coastal Cordillera west of Purico. After emplacement, the ignimbrites were modified by fluvial erosion, which formed curvilinear channels in the ignimbrites. In contrast to other ignimbrites in the region, there is little evidence of eolian erosion of the Purico ignimbrite. Eolian erosion takes much longer than fluvial erosion and it is possible that the Purico ignimbrite is too young to have been modified by wind action. Some surfaces of the ignimbrite have been affected by glaciation, giving them a smooth surface. This structure of the ignimbrite has been explained by magma chamber processes. Prior to the Purico ignimbrite eruption, a dacitic magma chamber already existed beneath the volcano. Probably after an injection of andesitic magma, dacitic contents of the magma chamber escaped upwards and formed the lowermost Lower Purico Ignimbrite. This injection of mafic magma rapidly increased the temperature and gas content of the dacite, causing the eruption to become a violent Plinian eruption with the development of an eruption column. This phase then drew onto denser dacitic magma, causing the column to collapse and the Upper Purico Ignimbrite and the "dacite dome D" to form. Post-ignimbrite activity Volcanic activity after the eruption of the ignimbrite has been subdivided into the older andesitic Purico group and the younger Chascon group. The first includes Cerro Negro, Cerro Purico, Putas and Cerro Toco which assume the structure of polygenetic volcanoes, while the latter is taken to include Aspero, El Cerillo/Chajnantor and El Chascon which are lava dome-lava flow structures. The Chascon group of domes is also the only one which contains mafic xenoliths. The Cerro Purico and Macon volcanoes formed a