Complex sentence: The oldest component clearly belonging to the volcano is the El Pozo ignimbrite that was erupted 258.2 ± 48.8 ka, forming a multi-layered ignimbrite that was probably generated by the injection of new, hot magma into older, cooler magma.
Split into simpler sentences: The oldest component clearly belonging to the volcano is the El Pozo ignimbrite which was erupted 258.2 ± 48.8 ka, forming a multi-layered ignimbrite. It was probably generated by the injection of new hot magma into older cooler magma.