Merapi has been quiet. No more hot clouds. Villages last October wedhus gembel crushed flat, now bustling dikunjung travelers. They took pictures in that location, then save them as memories.
But residents are still asked to be alert. Because the threat has not entirely gone. And this time the threat comes in the form of cold lava flood. Wednesday, January 5, 2011, for example,
cold lava flood that rolled from Merapi, then lunged Hamlet Gempol. Hamlet is situated in the village of Jumoyo, District Salam, Magelang, Central Java.The floods not only brings lava, but also a giant-sized stones. In the cold lava flood, Monday, January 3, 2011, large stones the size of the minibus hit the areas around the times Opak, Sleman, Yogyakarta.
Cold lava which swept Wednesday night, hit a bridge in Hail, up to collapse. Yogyakarta Magelang path-breaking. The houses residents in the vicinity of the river goes down. Not by water, but mud and sand that compact.
Flood also menghayutkan vehicle. Solidified volcanic material clog the river, causing a flow of lava and water turned into the garden and village. It was the biggest flood since Merapi erupted lava in 2010.
Gravity, not all material eruption of Merapi, which amount is estimated that 30 million cubic meters, has been dropped. "I estimate only 10 percent of flood-borne material. Still a lot at the top, "said Chief Hall Kegunungapian Investigation and Technology Development (BPPTK), Subandriyo, when contacted VIVAnews.com, Friday, January 7, 2011.
Subandriyo reminded that it is quite possible that a larger lava flooding will occur.
That is why, after monitoring the activity of Merapi, all officers now oversee BPPTK cold lava flood threat. Not only on the slopes, all the rivers that disgorge at the foot of Merapi lava flood potential. Moreover, when volcanic material is in compliance with river flow. "It's over," said Subandriyo. Thus, efforts to dredging and levee-making must be done immediately.
What is also urgent and should be paramount is the safety of residents in flood plains. When early warning appears, residents had no choice, must avoid the watershed, as well as flood overflow areas accessible.
Of note Meteorology, Climatology, and Geophysics (BMKG), based on rainfall data for over a decade last known Kaliurang region - the slopes of Merapi - occur on average monthly rainfall reached 508 millimeters in January and 514 millimeters in February.
The high rainfall in these months indicates that the peak of the rainy season at the peak of Merapi occurred in January and February of each year. That means in two months, cold lava flood is likely to threaten.
Learn from Colombia
Experts from BMKG, Daryono reminded that you should never underestimate the threat of cold lava flood. Because, he added, noting that history is not less deadly floods of lava erupting volcano. One example of flood disaster in the world's most destructive lahar was the post-flood lava eruption of Mount Nevado del Ruiz in Colombia in 1985.
At that time, within four hours after the eruption, which followed heavy rains, lava swiftly as far as 100 kilometers. Catastrophe ensued: more than 23,000 people were killed, about 5,000 people were injured, and more than 5,000 houses were destroyed along Chinchina, Guali, and the River Lagunillas.
The most severe damage upon the City Armero, located at the mouth of the Rio Lagunillas canyon. Three-quarters of the 28,700 city residents were killed in a tragic result of flood lava on November 13, 1985.
This terrible event is remembered as the next-Chinchina tregedi Armero. This is the most deadly lava floods recorded in history. "It is a fact that the impact of flood lava can actually do more harm than volcanic eruption itself," said Daryono, in a paper published BMKG site.
Another example is lava floods at Mount Pinatubo, Philippines. Since the eruption of 1991, lava floods had destroyed 100 thousand homes on the slopes and plains of the foot of the mountain.
Therefore, further Daryono, flood mitigation efforts need to be developed Merapi lava: lava flood early warning, monitoring and warning system in the form of lava flooding.
Equipment that is considered important, in addition to signal transmission and CCTV cameras have been installed at some point in the Merapi, is the operation of automatic rainfall monitoring system installed at the peak of Merapi. This tool is able to monitor the high intensity rainfall in telematri, realtime, and integrated in the monitoring center.
Another early warning instrument to consider is the system monitors the flow of lava that can detect ground vibrations during creep lava flood. "Most of this is possible to give early warning to minimize possible losses as small as either property or people resident in the vicinity of river channels that tipped at the peak of Merapi."
Moreover, to spend a deposit of volcanic material erupted results take three to four rainy seasons.
