Waited Entirely Lava

ecutiv e summary By Darmansjah

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

Phase of the eruption of Mount Merapi primary danger, like molten lava, pyroclastic, or burst of volcanic material, may have passed. However, secondary hazards still haunts the surrounding communities who tipped in the flood plains of Merapi.

Danger secondary lava flow (lava cold) is now the most formidable threat than other threats, such as flash floods or volcanic avalanches.
The Center for Volcanology and Geological Hazard Mitigation (PVMBG) Geological Survey- Surono said, amid heavy rainfall, there are two trigger lava flood, which is fine volcanic material (dust, grit, and sand) and pyroclastic deposits.

It is said, fine volcanic materials in large quantities can lead to flooding if the lava flow into the river and mixed water. This phenomenon can be seen from the cold lava flood events in all rivers in the west who tipped at Merapi.

Surono explained, vomit-volcanic material reached 150 million cubic meters-make a lot of fine material, such as dust and sand, spraying high into the air form the pillar of smoke. Based on data PVMBG, high pillar of smoke about 3 kilometers from the peak of Merapi. When energy is low, the material spreads in the direction the wind is now blowing westward eruption. As a result, a lot of volcanic material fell in the river west region, such as Pabelan, Lamat, White, and Krasak.

Once inside the river, fines will be mixed 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 large stone also influenced the high sliding 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 on the top but steep ramps in areas that have been built for public infrastructure. This contour causes the rate of lava more powerful rapids and big damage.

The second reason is the 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. Pyroclastic sediment there is in the depth of 30 centimeters below the water surface.

The temperature of 490 degrees celsius

Visually, visible volcanic material hardens outside but actually the inside is still hot, the temperature can reach 490 degrees celsius. The indication, and there's no smell belereng small eruption caused pyroclastic deposits met with an icy river water.

"Have to watch out for when sediments were eroded watersheds. It's dangerous for the communities along the river flow. 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, such as Boyolali district, will not be as bad as the western and southern regions. Areas north and east of the protected walls of the old Merapi is very solid, difficult to penetrate.

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

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

He warned, it took about three rainy seasons or three years to change the pyroclastic deposits into lava eruption of 2010. Hot clouds that are the largest and longest studies in the history of Mount Merapi in Indonesia. Power-to-12 km from the summit.

Surono said, the important thing is wary because no engineering technology that could restrain the rate of lava (cold). For residents about flood plains, especially in the bends of the river, are expected to evacuate temporarily. If there is a plan straightening and dredging the river, is expected to be done carefully and thoroughly for lava flow it becomes harder and harder  power.

Lili said it is working with Central Investigation and Technology Development volcano (BPPTK) Yogyakarta install remote monitoring equipment information (telemetry) in six rivers in the west and south of Merapi, as in White River, Boyong, Opak, and Krasak. Who monitored the condition of the river with cameras monitoring (CCTV), the vibration caused by geofon lava flow, and rainfall intensity. "Data from the telemetry is 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 the experience faced Merapi. Especially the people of Yogyakarta, cooperation and collaborative nature royongnya been tested time after the earthquake of 2006, "said Lili