The analysis of volcanic activity influences at the lower and middle part of Sentolo Formation, Kulon Progo using petrographic methodTri Winarno, Jenian Marin, Ilham Hani Pratama and Anis KurniasihMATEC Web of Conferences, 159 (2018) 01040DOI: https://doi.org/10.1051/matecconf/201815901040