Research indicates that subduction has been ongoing since the Jurassic 200 million years ago but accelerated 26 million years ago. After a phase of andesitic volcanism lasting from the late Tertiary to the Miocene, large scale ignimbritic volcanism commenced about 23 million years ago and is still ongoing. It began north of 21° southern latitude with the 23-18 million years old Oxaya formation and the 15-17 million years old Altos de Pica formation. Later the San Bartolo and Silapeti groups were generated, ending by the early Pleistocene. Volcanic activity at La Pacana is more recent than elsewhere in the region, with the oldest volcanic rocks that crop out in La Pacana being between 11 and 7.5 million years old. Large scale ignimbritic activity continued until 2 million years ago.