Geological Investigation and Risk Assessment for Disaster Management of Merapi Volcano and Surrounding Area, Yogyakarta Special Territory, Indonesia

Abstract

Mount Merapi is classified as one of the most attractive volcanos in the world. It is situated in Central Java and Yogyakarta Special Territory, Indonesia. It regularly erupts in every 4 years. Deposits produced by the activity of Mount Merapi are spread out in Sleman Regency Yogyakarta Special Territory, where the study area is located. The area includes four rock units, specifically Ancient Merapi, Middle Merapi, Recent Merapi, and Modern Merapi. Mount Merapi eruptions had been responsible of the collapse of Hindu Mataram Kingdom, Central Java, in the 10th to 11th century periods. This was demonstrated by the discovery of many ancient temples in Yogyakarta and surrounding areas, such as Temple Sambisari, Temple Kadisoka, and Temple Kedulan which were buried by volcanic deposits of Mount Merapi. The eruption of Mount Merapi, in the year 2010, recognized as the biggest eruption in recent decades, claimed about 300 lives and very large losses. The type of eruption changed from Merapi type in the activity period of 2006 and before to become the combination of Vulcanian type and Pelean type. Due to the very intensive activities of the volcano, the geohazard threats faced by people living in the surrounding area of Yogyakarta are high. And in the face of the volcanic disasters, the people of Mount Merapi unite in the implementation of disaster preparedness. In the study area, the geohazards are represented by lava flow, pyroclastic flow, ash fall, and lahar. There are four areas can reached by pyroclastic flow, including the Turi, Pakem, Cangkringan, and Ngemplak districts. All of the districts in the study area are threatened by ash fall, such as the Turi, Pakem, Cangkringan, Tempel, Sleman, Ngaglik, Ngemplak, Minggir, Sayegan, Mlati, Gamping, Godean, Depok, and Kalasan districts. While the areas threatened by lahar are Turi, Pakem, Cangkringan, Tempel, Ngaglik, Ngemplak, and Kalasan districts. By applying a scoring method, the study area can be classified into zone with high, moderate, and low geohazard vulnerability, threat, and risk.