The Characteristics of Lahar in Merapi Volcano, Central Java as the Indicator of the Explosivity during Holocene

Abstract

Merapi Volcano in Central Java has been the most active volcano during Holocene time. As a strato volcano, Merapi exhibits alternating volcanic activities of effusive and explosive characters and self destruction. The explosivity index has evolved during the last ten thousand years. The effusive activities were characterized by the occurrence of lava flows, the development of lava dome, and the production of the "nuee ardente d'avalanche" called Merapi type. The explosive stage is frequently accompanied by the occurence of pyroclastic flows. The present investigation is attempted to reveal the relationship between the characteristics of lahar and the evolution of the activity of Merapi Volcano. The quantitative analysis was focused on the size and shape of the lahar components particularly that of pumice as the main indicators in 73 measured stratigraphic columns of lahar deposits. In addition, the main chemical element rim structures of hornblende identified in lahar components indicate the different lahar units. There are five lahar units and five groups of Merapi activities which can be distinguished. It can be concluded that the characteristics of lahar reflect the evolution of the activities in the past. The risk analyses of Merapi Volcano therefore can be enlarged to cover the possible hazard based on the lahar characteristics.

Volcanic Eruption Products and Its Slope Stability in Merapi Volcano, Yogyakarta

“…This deposition at the Merapi is relatively young (< 1811) [4]. Its relation with the units of Kinahrejo pyroclastic units is that the unit of Laharic deposited on the stage Kuning River Merapi is young and aligned.…”

“…To determine the age of this unit, the author refers to previous researchers through field data observation. The Holocene age of this unit was the result of recent deposition of Merapi (< 1811) [4]. It was deposited at the Merapi with a range of new age (< 1811).…”

Detecting Deformation Due to the 2018 Merapi Volcano Eruption Using Interferometric Synthetic Aperture Radar (Insar) From Sentinel-1 Tops

“…The explosive stage is frequently accompanied by pyroclastic flows (Sudradjat et al, 2010). Merapi is known for its frequent small to moderate eruptions, pyroclastic flows produced by the collapse of the lava dome, and the large population that has settled on and around the flanks of the volcano that are at risk.…”

Geomorphology of the Southern Flank of Merapi Volcano in Relation to the Potential Hazards and Natural Resources: A Review

“…even it belongs to the most active volcano during holocene (Sudrajat et al, 2010). As an active volcano, the history of its eruption has lasted for a long time.…”

“…The volcanic activity of Merapi is characterized by a loop between explosive and effusive activity and self-destruction. Effusive activity is characterized by lava flow and lava dome formation which produces nuee ardente d'avalanche of Merapi type (Sudrajat et al, 2010). The history of Merapi eruption has been well recorded since 1978 even since 1006.…”