record of multiple highly explosive mafic eruptions from Gunung Agung (Bali, Indonesia): implications for eruption frequency and volcanic hazards Sacred mountains Stratovolcanoes of Indonesia Volcanoes of Bali VEI-5 volcanoes Active volcanoes of Indonesia 20th-century volcanic events 21st-century volcanic events Karangasem Regency Mountains of Bali Holocene stratovolcanoes