Waiting entirely Lava

Waiting entirely Lava

Solfatara smoke billowed from the crater of Mount Merapi as seen from the hamlet Kinahrejo, Umbulharjo, Cangkringan, Sleman, Yogyakarta, Sunday (30 / 1). Niche of lava down the road heading south so the area north of Mount Merapi are relatively safer from the threat of cold lava.

by Cornelius Helmy executive summary by darmansjah

Phase of the primary dangers of an eruption of Mount Merapi, as leleran lava, pyroclastic, or a burst of volcanic material, may have passed. However, secondary hazards still haunt the people around the banks of rivers that disgorge at Merapi.

Secondary lava flow hazards (lava cold) is now the most powerful threat than other threats, such as flash flood or volcanic avalanches.

The Center for Volcanology and Geological Hazard Mitigation (PVMBG) Geological Agency Surono said, amid high rainfall, there are two triggers floods of lava, which is fine volcanic material (dust, grit, and sand) as well as heat clouds precipitate.

It is said, fine volcanic material in large amounts can trigger a flood of lava when the incoming stream and mixed with water. This phenomenon can be seen from the cold lava flood events in all rivers in the west that disgorge at Merapi.

Surono explained, vomit-volcanic material reached 150 million cubic meters, making a lot of fine material, such as dust and sand, spray high into the air to form pillars of smoke. Based on data PVMBG, tall pillar of smoke reaches 3 kilometers from the peak of Merapi. When energy is depleted, the material spreads in the direction of wind during the eruption blew westward. As a result, a lot of volcanic material fell in the river west area, such as Pabelan, survived, White, and Krasak.

Once entered into the river, smooth material will mix with water so that the density of river water increases and more powerful. Not surprisingly, the material streams, such as large rocks, very easy to lift and float. The power lift boulders also influenced the high slip properties of water mixed with volcanic ash.

"Stone of the drift was mostly already in the river and not vomit eruption of 2010," he said.

Geographical conditions in the west of Merapi is contoured at the top but steep ramps in areas that have been built for public infrastructure. This contour causes the rate of lava more swift and powerful big damage.

The second cause is volcanic deposits of pyroclastic activity. This is seen in the river south of Merapi, there are 30-40 percent, where there Gendol River and Opak. Sediment clouds the heat over there at a depth of 30 centimeters below the water surface.

Temperature of 490 degrees celsius

Visually, the hardened volcanic material visible on the outside but actually the inside is still hot, the temperature may reach 490 degrees Celsius. The indications, and there's no smell belereng small eruption caused pyroclastic deposits met with the cold river water.

"You have to watch out for when sediments were eroded watersheds. It's dangerous for people throughout the watershed. Some common infrastructure can also be affected, such as airport Adisutjipto and temples around Gendol River, "he said. Impact of flood lava to the east and north of Merapi, as Boyolali District, will not be as bad as the western and southern regions. Areas north and east walls protected the old Merapi very solid, impenetrable.

Delivered a similar warning Prevention Directorate Head of Disaster Risk Reduction National Disaster Lilik Kurniawan. He said, with the intensity of the torrential flood of lava and a big, old river channel at the White River is open again because of the nature of the lava floods tend to move straight.

It looks at the Village Sirahan, District Salam, Magelang regency, Central Java. This area originally was a long line of White River bridge closed for construction.

He warned, it took about three rainy seasons or three years to change the 2010 eruption pyroclastic deposits into the lava. Hot clouds it is the largest and longest study of the history of Mount Merapi in Indonesia. Its range as high as 12 km from the summit.

Surono said, the important thing is wary because no engineering technology that could withstand the rate of lava (cold). For residents of the surrounding flood plains, especially in the bends of the river, are expected to evacuate temporarily. If there are plans straightening and dredging the river, expected to be done carefully and thoroughly so that the lava flow actually becomes harder and harder hit power.

Lilik said it is working with the Center Kegunungapian Investigation and Technology Development (BPPTK) Yogyakarta install remote monitoring equipment information (telemetry) in six rivers in the west and south of Merapi, as in the White River, Boyong, Opak, and Krasak. Which monitored the condition of the river with cameras (CCTV), the vibration caused by geofon lava flow, and intensity of rainfall. "Data from the telemetry was to map areas that are safe," he said.

Also done volunteer assistance from the Forum to monitor Merapi lava flow visually and reported via radio communication.

"The community has an important role. They are solid and have experience of dealing with Merapi. Yogyakarta Special community, cooperation and mutual nature cooperate tested during earthquake of 2006, "said Lilik