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Volcanic mud threatens Prambanan Temple
Powerful flows of volcanic mud carried by rivers from Mount Merapi that have destroyed bridges, houses, farmlands and other structures along river banks also pose a threat to the Prambanan Temple
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owerful flows of volcanic mud carried by rivers from Mount Merapi that have destroyed bridges, houses, farmlands and other structures along river banks also pose a threat to the Prambanan Temple.
The famous Hindu temple complex, located in Prambanan on the border of Yogyakarta and
Central Java provinces, sits 100 meters from the banks of the Opak River, a confluence of the Petit Opak and Gendol Rivers that flow from Mt. Merapi.
Prambanan, a ninth-century Hindu temple compound — a UNESCO World Heritage Site — is the largest Hindu temple in Indonesia and one of the largest Hindu temples in Southeast Asia.
In 1006, large eruptions on Mt. Merapi covered the Buddist temple of Borobudur in Magelang, Central Java, in ash, where it lay hidden for centuries under ash and jungle growth.
An official from the Volcanic Technology Development and Research Center (BPPTK) in Yogyakarta, Dewi S. Sayudi, said the threat to Prambanan was immense because the upper streams of both the Opak and Gendol Rivers carried large amounts of volcanic debris from the 2010 Mt. Merapi eruptions.
“The lahar that we have seen so far is just the tip. The flows carry only a small portion of the thick layers of volcanic debris from the slopes of Merapi,” Dewi said recently.
The eruptions in October and November, Merapi’s most powerful in a century, were estimated to
have spewed more than 150 million cubic meters of volcanic debris consisting of large rocks, stones, sand and ash.
Hours of heavy rain over the peak of the world’s most active volcano turns the thick layers of heated volcanic debris into powerful mudflows that speed their way down the slope, sweeping away all in
their path.
Thick deposit of volcanic debris extending 15 kilometers along the banks of the Gendol River has raised the water level dramatically.
This has resulted in a vast wall of volcanic debris 1.5 kilometers in width and more than 10
kilometers long flowing to the Opak River.
The thick layer of heated volcanic debris means rainwater runoff adds to the risk of more lahar.
Experts predict that the threat of lahar from the eruptions could remain for the next three years due to the massive volume of the volcanic debris.
Despite the threat, no preparations have been made so far by Prambanan Temple officials, who continue to monitor the flow of the Opak River as rainfall increases as Indonesia heads into the peak of the wet season.
The head of the Serayu-Opak River Region Agency, Bambang Hargono, said all the dams set up to stop volcanic debris were at full capacity.
“Apart from evaluating the conditions, we also plan to dredge the river to normalize the stream and reduce the risk of lahar next year,” he said.
Lahar has so far devastated areas along the banks of the Opak River in Argomulyo subdistrict in
Sleman, Yogyakarta, located 14 kilometers from the peak of Mt. Merapi, destroying houses and farmlands.
