Volcano Case Study: Mount Merapi

Mount Merapi is a stratovolcano comprised of layers of hardened lava, rocks, and ash from the previous eruptions. The lave vault that developed in May 2006 did so under the residues of old magma dome as it was reported by the New York Times; making it difficult to dislocate. As of early June, the indigenous people, and the volcanologists were still waiting for the volcano's next action. I choose to study Mount Merapi because it is the most dangerous volcano in the world that influences the activities of thousands of individuals. For these reasons, many societies refuse to leave their homes or their livestock, only to be agonized by the earthquake.

Moreover, The Merapi volcano is situated at 25 km north of the Yogyakarta, and it rose from the South-North subduction of the Indian oceanic plate underneath the Java arc structure. The subduction produces a line of active volcanos from Bali, Java, and Sumatra, and continues until Nusa Tenggara Island. The volcanos sequence is considered as the very vigorous of the Pacific Ring of Fire, with the Mesozoic subduction creating a dike of 6 to 7 km deep. Further, it is situated at the intersection between two main orientations of volcanoes, developed in late Pleistocene to early Holocene. The Ungaran, Marbabu, Telomoyo, and Merapi from the North to the South are the first volcanic belt. The second one is from East to West direction consisting of Sumbing, Sindoro, Merapi, Slamet, and Lawu volcano. The Merapi volcano has a predictable feature of collapsing and constructing lava dome, which is revealed by the similarity of distinguishing lava basaltic into andesitic in every age. Constructing Merapi begun in Pleistocene at Gunung Turgo, Plawangan, and Gunung Bibi, which formed basaltic magma. The features of the Merapi volcano entail extrusions of the glutinous magma creating lava vaults at the peak of the mountain, continued by gravitational volatility and collapse of these magma vaults to generate pyroclastic at systematic interludes (Walaningsih et al., 203).

Equally important, the two current eruptions at Mt. Merapi climaxed in 2001 and 2006 and both tremors in these preceding years had a scale of Mw 6.3. Before the 2001 quake, the temperatures were about 435 degrees Celsius (Walter et al p.2). Moreover, Mount Merapi commenced a new eruptive stage after 4.5 years of dormancy. In 2006, a slow escalation of the seismicity was discovered, and about 10,000 dwellers were advised to relocate. At this period, Mount Merapi was already in a level of advanced volcanic motion, with the Indonesians-German collaboration scheme MERAPI closely observing this action. In mid-May, 22,000 people were evacuated when the alarm intensities elevated from three to four, which was the highest level. Moreover, an earthquake, with a scale of Mw 6.3, 16 days after the first pyroclastic avalanche, occurred at 5.53 local time. The complexity of the quake was at 130 km, thus, equivalent to the depth of the subducting block under this region. Within an area as large as 500km2, the tremor caused 6,000 mortalities and extensive destruction of the infrastructure. Further, 537 pyroclastic avalanches (PA) struck, during the 16 days preceding to the tremor, which imply a mean of 34 in a day. 16 days after the quake, the dome growth was 50,000m3; however, the vault movement improved to 1523 PA an average of over 95 PA in a day (p.2).

Besides, the explosion at Merapi was the most devastating incidence, which took place in 2010. It produced more than 100 pyroclastic currents, with an enormous scale of volume, energy, and destruction (Kelfoun et al., p.5). The commotion was well examined and detected, and the sequence of events can be reassembled. Furthermore, in spite of the clouds that shielded the volcano during much of the eruptive chapters, real-time monitoring of the volcanic motion and recording of the magnitude of the PDCs were incorporated using geophysical statistics, and locator descriptions. At 26 October at 17.02, the first eruptive stage started at local time (UV+7). A concentrated phreatomagmatic eruption from a shallow lava invasion formed a crater 200m wide and 100m deep. The explosion demolished the thin lava incursion and the old summit cupola compound, and it displaced the conduit filled volatile-rich pumice over several kilometers. A magma dome emerged on 29 October that is after a short period of tranquil, as demonstrated by incandescence. On November 3, a chain of magmatic blasts accompanied by a parallel growth and destruction of the magma vault that ruptured the Southern part of the summit crater produced PDCs 12 km in length. The new peak magma vault was recreated to a volume of ~ 5x106 m3 on November 4. Further, the movement peaked on November 5 after 00:02 local time with a sequence of dome bursts and reverting downfalls that demolished the new dome (p.5).

Moreover, another explosive period instigated reverting collapse of an enormous portion of the summit and trailed by a subplinian level between 02:11 and 04:21 local time. A convective cloud that ascended to more than 15 km in height was produced which generated disseminated pumice cascades, and reedy moveable pumiceous PDCs channelized in the Gendol valley. After November 8, the seismic action slowly began to reduce in concentration. The satellite records specified that the vault progression ended by 8 November following a short12 hour-long rhythm at a remarkable rate of ca. 35m3 S-1 (p.6). The gushes shattered a region of 22 km2, much larger than the currents. On ridge tops and interfluves, the dilute tide made distinctive thin, Wave-bedded to enormous, sandy, and erosive stream sediments that locally have depositional and influence landscapes naturally of extreme-energy explosion (p.8).

Of equal importance, the Code River, which runs through the Yogyakarta, overflowed; bringing thousands of heaps of the volcanic substance from Mt. Merapi that had exploded since the previous days. The volcano besieged hundreds of homes along the riverbanks and made 500 people to evacuate their houses. Moreover, when the mudflow reduced, the societies resumed and constructed their dwellings, leaving the calamity prone region. Besides, because of the topographical features, the inhabitants of the Code riverbank are likely to grieve due to the occurrences of the explosions. The development of the suburbs has gradually advanced causing the inhabitants prone to the environmental threat, which is against the government regulation commonly termed as Wedi kengser (Hapsari, p.2). However, the people have built the non-permanent dwellings, and most of these settlements are heritable through the generations. In 2005, according to the Yogyakarta statistic office, around 30,000 citizens lived along the riverbank. In the Yogyakarta province, the Code River runs through the three localities namely, the Bantul District, Sleman District, and the Yogyakarta Municipality.

Furthermore, Yogyakarta was developed back in 1755 after the Giyanti Agreement, which separated the control of the empire into two: Yogyakarta and Surakarta. The existence of the Dutch regime brought the improvement of several public amenities, for example, fort, railway stations, banks, government offices, post offices, and the government residential (p.7). The foreign regime had commercialized the inhabited zone, first in the Eastern side of the Fort Vrederburg, then in the Northeast part of the Yogyakarta known as Kotabaru, which was aimed at accommodating the white settlers while relocating the native communities. Further, the Indonesian administration established the phase of urban transformation in the city during the Suharto era in 1966. The populace in Yogyakarta progressed from 532 to 979 individuals per km2 in 1970 through 2000. The progression of the new urban community was doubled in the year 1993-2006; however, it caused the farming land to decrease by 25%. (p.8). Furthermore, the Indonesian administration has emphasized on upgrading and reorganizing of the urban space in the Code riverbank providing inadequate space for the poor people. The housing access is relatively affordable to those people with high economic income. The deprived urban dwellers have been pushed to look for accommodation inside the Kampung, which is cheap, or an unoccupied region where they can construct their houses and maintain it at a lower cost. In Indonesia, the formal designers go through the official certification including, construction, marketing, and sales procedures, which is easily regulated by the local regime. On the other hand, the unauthorized developers work below the board and are outside the development regulatory scheme (p.9). The management is incapable of monitoring the growth undertakings much less control them.

Conclusion

To conclude, the volcano chain is the most active of the Pacific Ring Fire with Mesozoic subduction forming a trench of 6 to 7 km deep. The Merapi volcano has a distinctive aspect of collapsing and building lava dome to form pyroclastic flows at regular intervals. The administration of Indonesia should transform the political-economic settings by restructuring new rules to govern its citizens equally to improve the livelihood of the people in the Code riverbank.

Works Cited

Hapsari Maharanani. The political ecology of human vulnerability to Merapi eruption 2010. 2018. www.respect.osaka-u.ac.jp/.../The-Political-Ecology-of- Human-Vulnerability-to-Merapi...

Kelfoun Karim, Gueugneau Valentin, Jean-Christopher, Aisyah Naning, Cholik Noer, and Merciecca Charley. Simulation of block-and-ash flows and ash-cloud surges of the 2010 eruption of Merapi volcano with a two-layer model. 2017. https://hal-clermont-univ-archieves-quovertes/hal-01684796/document.Pdf

Walter, Wang, Zimmer, Grosser, Lahr, and Ratdomopurbo. Volcanic activity influenced by tectonic earthquakes: state and dynamic stress triggering at Mt. Merapi. 2006 Ftp://ftp.gfz-potsdam.de/home/turk/twalter/walter_etal_merapi2006Glo28710.pdf

Walaningsih, Humaida, Harjoko, and Watanabe. "Major elements and rare earth elements investigation of Merapi volcano, Central Java, Indonesia." Procedia earth and planetary, vol. 6(2013), 2012, 202-211. Science Direct.