Ratdomopurbo, learning the ways of Merapi<\/p>\n
By Asip A. Hasani<\/p>\n
YOGYAKARTA (JP): \"Let Merapi residents' mystical calculations
\ndecide if they will vacate their village or not, because we
\nscientists cannot determine if and when the volcano will erupt.\"<\/p>\n
This statement was made by volcanologist Antonius
\nRatdomopurbo, chief of the Volcanic Technology and Research
\nDevelopment Station (BPPTK) in Yogyakarta.<\/p>\n
Purbo, as he is more commonly known, is one of the key people
\nresponsible for determining the danger level of the rumbling
\nvolcano. Last August, the status was Waspada (caution), before
\nbeing raised to Siaga (alert) on Jan. 10, 2001 and then raised
\nagain to the top level Awas (eruption imminent) on Feb. 10.<\/p>\n
Merapi's behavior is wildly unpredictable. People living at
\nthe foot of the world's most active volcano have their own
\nmystical ways to assess the danger level, believing that the
\n\"modern\" equipment scientists use are not entirely accurate. So,
\nvolcanologists like Purbo, who has been watching Merapi for 15
\nyears, choose to compromise.<\/p>\n
\"We are now watching the lava dome on Merapi's peak which may
\nslide at any time without warning,\" he said.<\/p>\n
The lava dome consists of an estimated 1 million cubic meters
\nof volcanic material, piling up following a series of recent
\nexplosions.<\/p>\n
If the dome collapses, it means disaster. The sliding mass of
\nlava turns into dreaded burning clouds of lava with a temperature
\nof up to 600 degrees Celsius, moving at a speed of around 90
\nkilometers per hour.<\/p>\n
\"We do hope that the dome will stay put for a long period of
\ntime, or slide by small fractions so that it will not pose any
\ndanger,\" said Purbo.<\/p>\n
The heat clouds were the most dangerous results of Merapi's
\nexplosions throughout the 20th century, when explosions were less
\nviolent than those during the 19th century, particularly in 1872.<\/p>\n
The largest eruption in the 20th century occurred in 1930,
\nleaving more than 1,300 people dead. \"Still, heat clouds were the
\nmain killer,\" Purbo explained.<\/p>\n
Merapi's heat clouds are also the most unpredictable
\nphenomenon of the volcano.<\/p>\n
The volcano's Nov. 22, 1994 eruption demonstrated how its 2.5
\nmillion cubic-meter lava dome could unexpectedly drop, despite
\nthe volcano's activity status being set at the lowest level.<\/p>\n
The heat clouds generated by the collapse of the lava dome
\ndescended upon Turgo village on the southern slope, killing 64
\nresidents.<\/p>\n
\"It was a gravitational collapse which was more a consequence
\nof landslide than volcanic phenomenon from what we could detect,\"
\nsaid Purbo, who was born in Gunung Kidul regency on Feb. 5, 1961.<\/p>\n
\"Now we realize that studying Mount Merapi is not only a study
\nof volcanology, but of landslides and earthquakes too,\" he added.<\/p>\n
Purbo obtained his bachelor degree in 1986 from Gadjah Mada
\nUniversity, Yogyakarta. His thesis concentrated on the
\nrelationship between the Indian Ocean's waves and Mount Merapi's
\nvolcanic activity.<\/p>\n
Assisted by a scholarship from the French government, Purbo
\ncontinued his Geophysics research at the University of J. Fourier
\nGrenoble, in France, where he obtained his doctorate. He wrote
\ntwo research papers on Merapi during his studies in France, Etude
\nde Seismes de Type-A du Volcan Merapi (A Seismic Study of the
\nType-A Merapi Volcano) and Etude de Seismologique du Volcan
\nMerapi et Formation du Dome de 1994 (A Seismological Study of the
\nMerapi Volcano and Formation of the 1994 Lava Dome).<\/p>\n
The Jakarta Post's Asip A. Hasani interviewed Purbo recently
\nat his BPPTK office on Mount Merapi, located on the border
\nseparating the Yogyakarta and Central Java provinces. Following
\nare excerpts from the interview:<\/p>\n
Question: Mount Merapi hasn't generated a large, explosive
\neruption for years, so what makes the volcano remain so
\ndangerous?<\/p>\n
Answer: The heat clouds have been the most dangerous. The
\npossibility of poisonous gases and stones raining down is not
\nlikely to occur. Even during the largest eruption (ever recorded)
\nin 1872, heat clouds were the biggest danger.<\/p>\n
How dangerous would a heat cloud be generated during the
\ncurrent activity?<\/p>\n
It is possible that a massive heat cloud could be generated
\nfrom the one million cubic-meter lava dome formed mostly in 2001,
\nwhich is currently in a critical position. Part of it slid on
\nFeb. 10. Massive heat clouds could occur if the entire 2001 lava
\ndome collapsed at the same time. The disaster could even be more
\nunthinkable if the 1997 and 1998 lava remaining underneath also
\nslide at the same time. Together, they constitute some seven
\nmillion cubic meters of lava.<\/p>\n
What factors could cause the lava dome to collapse?<\/p>\n
There are at least four factors: earthquake; heavy rains which
\nfall on the volcano's summit for an extended period of time; the
\ndrop of new lava from the top; or a fresh supply of volcanic
\nmudflow from the earth piling up on the lava dome that could push
\nthe mass down.<\/p>\n
How could a collapse of the 2001 lava dome threaten Merapi
\nresidents?<\/p>\n
Massive heat clouds will form if at least 80 percent of the
\none million cubic-meter 2001 lava dome collapses in the direction
\nof the residential areas.<\/p>\n
How could 1994 heat clouds descend on Turgo village and kill
\n60 residents?<\/p>\n
It was part of the unpredictability of Mount Merapi. First,
\nthe 2.5 million cubic meters of volcanic material contained
\nwithin the 1994 lava dome collapsed on Nov. 22, 1994 when all
\nvolcanic precursors decreased to the lowest level for several
\ndays. Merapi's volcanic activity was at its peak between April to
\nMarch and only declined in August.<\/p>\n
Nobody expected that three months later almost 100 percent of
\nthe lava dome would suddenly drop without any detectable trigger.
\nOur six-member monitoring team was even on the volcano's summit
\nexamining debris from the 1994 volcanic activity when the dome
\ncollapsed, but did not realize it. That is what is called a
\n\"gravitational collapse\".<\/p>\n
I was in France at the time but wrote a letter to BPPTK's head
\nto issue a warning.<\/p>\n
Second, the heat cloud hit Turgo village by surprise.<\/p>\n
There were many unpredictable events during 1994 eruption;
\nwhat have you learned from that experience?<\/p>\n
We are more careful in predicting any potential disaster.
\nThat's why I study landslides too, not only volcanology. We are
\ntrying to determine signs of landslide or gravitational collapse.
\nUnfortunately, Mount Merapi is shrouded by a thick haze most of
\nthe time which makes it difficult for us to observe any physical
\nchanges to the volcano's lava domes.<\/p>\n
How active is Mount Merapi?<\/p>\n
The volcano is never asleep. It discharges hot lava at least
\nonce a day when in its quietest state. The volcano never stops
\nerupting geologically.<\/p>\n
After 15 years observing Merapi, what is the most important
\nlesson you have learned?<\/p>\n
Gravitational collapse of the volcano's lava dome is now one
\nof the most difficult mysteries to solve. I hope that there is a
\ntrigger to the collapse and that we can soon discover it. If not,
\nnobody can predict a 1994-style disaster.<\/p>\n
What do you think about the Merapi residents' belief that
\ntheir elders can have a mystical vision warning when the volcano
\nwill violently erupt?<\/p>\n
Their belief is based on experience they have obtained from
\ngenerations upon generations. However, I don't believe in
\npredictions declaring that the next explosion will definitely
\nhappen on a particular day.<\/p>\n
They already know safe places to hide on the slope of the
\nvolcano in case of eruption. It's probably true that some of them
\nhave supernatural visions but they should not make them public
\nbecause their reliability is highly questionable.<\/p>",
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