Mount Merapi “Mountain of Fire” Java, Indonesia Matt Treveloni & Ryder Arsenault Department of Geology @ Colby College

Location Pacific Ring of Fire 30 km North of Yogyakarta, Indonesia Destructive plate margin (Indo-Australian Plate & Eurasian Plate)

Form & Dimensions Stratovolcano Elevation: 2,930 m, 1,356 m above ground Summit is higher on the North, lahars and pyroclastic flows run down the South side Years of eruptions created distinct trench

Eruptions Fault line: Sunda-Banda Arc Subduction of Indo-Australian Plate under the Eurasian Plate (twice as thick) Erupts: Hot gas, ashes, volcanic bombs (pyroclastic flows, lahars) Mt. Merapi erupts every 4-5 years with bigger eruptions every decade (2010), but smoke is seen emerging 300 days a year! FUN FACT!

Rocks & Deposits Most of the lavas from Merapi are high potassium basaltic andesites. The lava from Mt. Merapi is mainly porphyritic. Plagioclase and clinopyroxene are the most common phenocrysts. Silica content ranges from 52 to 57%. Phenocrysts can occupy up to 60% of the total rock volume in Mt. Merapi’s lava.

2010 Eruption It was a VEI 4. Pyroclastic flows reached 11.5km to the west, 15 km to the south, 4km to the north and 7km to the east.

Effects of the 2010 Eruption Fun Facts The safe zone for the 2010 eruption was 20 km from the volcano. Over 4 million people live within 30 km. Dome Collapse Over 300,000 people were forced to evacuate their homes. Crop Destruction

Why is Mt. Merapi So Dangerous? Mt. Merapi has produced more pyroclastic flows than any other volcano in the world Only 30 km away from Yogyakarta (population ~400K) which lies directly in flow path Indonesia’s intense rainfall causes massive lahars

Culture & Other Info Considered sacred by local people, they believe that a supernatural kingdom exists at the summit and a priest makes an offering once a year Ash leads to fertile soil Conservation area (unsafe to live) and illegal to climb to summit Tourism lies in museums No geothermal energy or hydrothermal activity

Monitoring Seismology There are 8 seismograph stations in the network. Volcanomagnetism Since 1977 they monitor the magnetism beneath the Earth’s surface. Deformation Three GPS signals measure to make sure the distance and angles between all three remain the same. In 1990 they introduced tilt monitors to measure deformation. Geochemistry There are two solfatara fields used for measuring the volcanic gases. Lahar Detection Lahars are usually triggered by heavy rainfall. An acoustic sensor measures the noise given off by a lahar in order to detect when one begins moving.

References Marliyani, G.I., 2010: An Overview of Merapi Volcano, Central Java, Indonesia, at http://mountmerapi.net/mount-merapi/ (accessed 22 January, 2015) Leontiou, A., 2010: FAQ: A Look Inside Mount Merapi, at http://www.livescience.com/11081-faq-mount-merapi.html (accessed 24 January, 2015) Lavigne, F. & Thouret, J.C., 2003: Sediment transportation and deposition by rain-triggered lahars at Merapi Volcano, Central Java, Indonesia, at http://www.sciencedirect.com/science/article/pii/S0169555X02001605 (accessed 23 January, 2015) Seach, J., 2012: Merapi Volcano, at http://www.volcanolive.com/merapi.html (accessed 25 January, 2015) Simkin, T. & Siebert, L., 1994: Volcanoes of the World, at http://volcano.oregonstate.edu/oldroot/volcanoes/merapi/merapi.html (accessed 25 January, 2015

References Boston.com 2010: Mount Merapi’s eruptions at http://www.boston.com/bigpicture/2010/11/mount_merapis_eruptions.html (Accessed 25 January, 2015) Geotalk, 2012. Mt. Merapi Eruption at http://www.geotalk.info/#!mt-merapi/c21bv Gertisser, R. 2003: Temporal Variations in magma composition at Merapi Volcano at http://www.sciencedirect.com/science/article/pii/S0377027303000258 Smithsonian Institution, 2013: Global Volcanism Program at http://volcano.si.edu/volcano.cfm?vn=263250 (Accessed 25 January, 2015) Youtube 2010: Merapi Eruption: Travel chaos as volcano spews massive clouds of ash at https://www.youtube.com/watch?v=nEBTfQ79Z7A (Accessed 25 January, 2015)