Complex sentence: The caldera was at first considered to be large with a centre around, coinciding with the Vilama depression and with vents on the eastern margin beneath the Cerro Caucani, Cerro Solterío, Campanario and Coyaguayma volcanoes, which generate the Abra Granada volcanic complex.
Split into simpler sentences: The caldera was at first considered to be large with a centre around, coinciding with the Vilama depression. Vents were localized on the eastern margin beneath the Cerro Caucani, Cerro Solterío, Campanario and Coyaguayma volcanoes, which in turn make up the Abra Granada volcanic complex.