Gravitational Collapse and Explosive Eruption of Mount Popa Volcano, Myanmar: Implications for Tectonics and Geohazards
About the Event:
Mt Popa is one of the legendary volcanoes in mainland SE Asia. It is a dormant volcano 1518 metres above sea level and located in central Myanmar in the Mandalay Region, about 50 km southeast of Bagan, a major tourist site in central Myanmar. Mount Popa is perhaps best known as a pilgrimage site, with numerous spiritual Nat temples and relic sites atop the mountain and at Taung Kalat, a sheer-sided volcanic plug (neck) at the southwest of Mt Popa, which rises 660 metres above the sea level. The Taung Kalat is sometimes confused with main Mt Popa volcano with its crater blown open on one side and is called Taung Ma-gyi (main volcanoe). The volcanic crater itself is about 1.6 km in diameter. The volcano is built on Pliocene sandstones of Ayeyarwaddy Formation. Its complex volcanic edifice is composed of lava flows and domes; the composition ranges from basalts to dacites. Potassium-Argon age obtained from one of the lava flows provided the age 4.30 ± 0.55 Ma (Crow and Khin Zaw, 2017). A local legend reported that Mt. Popa could have had an eruption at 800 BP and 442 BCE. We attempted to determine the timing and type of the most recent eruptions of the volcano (as well as the origin and age of relatively recent volcaniclastic fan coming out from the crater breach previously described as lahar or debris flow by Stephenson and Marshall (1984) (Belousov et al., 2018). We have determined that the major part of the young volcaniclastic fan represents typical debris avalanche deposit (5=27 km2, v~3 km3, H=l.1 km, L= 11 km, H/L=0.1). In its proximal and NE parts the surface of the fan is smooth, covered by deposit of scoriaceous pyroclastic flow. The contact between the avalanche and the pyroclastic flow indicates no significant depositional time gap. Probably the edifice of Mount Popa was destabilized by intrusion of magma and the collapse triggered explosive eruption. No blast deposit was found in the area, so the collapse scenario was of Shiveluch type (Belousov et al., 2018). Along its outer boundaries the avalanche scraped and displaced the underlying deposit of Arrawaddy Formation. Under the bulldozed sandstones, we found two layers of buried paleosol separated by thin layer of fine-grained ash. Calibrated C14 ages of the paleosol layers are correspondingly 12820-12650 and 8590-8400 BP. Paleosol on top of the volcaniclastic fan provided a calibrated C14 age of 2700-2640 BP (analyses by Beta Analytic). We conclude that the latest period of volcanic activity of Mt Popa took place in the beginning of Holocene associated with the eastward subduction of India Plate. It included several mild explosive eruptions probably of vulcanian type ~ 12700-8500 BP, followed by large scale edifice collapse~ 8000 BP, then followed (probably immediately) by strong magmatic eruption with deposition of the PF. We have not found evidences of the eruptions ~800 BP and 442 BC; further work on to understand the crater wall collapses, mudflows and volcanic facies etc. in the area due to potential for future eruptions and geohazards as of recent landslides reported in October 2017. The heavy monsoonal rains caused the problems as the volcano is composed of soft and loose volcanic sandstones, ash and lahar as well as deforestation making the soil erodible and more susceptible to landslides.
About the Speaker:
Prof Khin Zaw is Professor of Economic Geology, CODES Centre of Ore Deposits and Earth Sciences, School of Natural Sciences at the University of Tasmania. He received BSc from Yangon University in 1968, FGA Diploma (Fellowships of Gemmological Association of Great Britain) in 1969, MSc from Queen’s University, Kingston, Ontario, CANADA in 1976 and PhD from University of Tasmania in 1990 and joined CODES Centre. He has well over 40 years’ experience working in Canada, Australia, New Zealand, China, Japan and SE Asian countries. He has published more than 120 referred papers and is an internationally recognized geoscientist for his work on geochronology, tectonics and metallogeny of mainland SE Asia.
He currently serves as an Associate Editor of an internationally recognized, peer-refereed Journal of Asian Earth Sciences (JAES) and recently co-edited and published a Geological Society of London (GSL) Memoirs on ‘Myanmar: Geology, Resources and Tectonics’. He is a Fellow of the Australian Institute of Mining and Metallurgy and a Fellow of Society of Economic Geologists and recently bestowed with an Honorary Life Fellowship from Geological Society of London recognizing for his global contribution to the Geoscience to join in the list of other pre-eminent scientists in the world.