Mount Rinjani volcanic complex, Lombok Island,
Indonesia. Image by mohd farid / Shutterstock
It was
like an episode of Cold Case. With volcanoes.
Researchers
relied on a combination of polar ice cores, tree-rings, geochemistry and a
medieval chronicle little-known in the West to solve one of vulcanology’s most
enduring mysteries: Which peak blew its top in the mid-13th century, causing a
catastrophic eruption that ranks as one of the biggest in recorded history?
As with
any investigation, the team had to rule out other suspects as it followed a
trail of clues — and even read palms, or at least palm leaves. The culprit of
the massive 1257 AD eruption, researchers say, is Samalas volcano, on Lombok
Island in Indonesia.
Searching for Volcano Suspects
For
decades, scientists have been searching for the volcano responsible for the
largest spike in sulfate deposits in the last 7,000 years, which were revealed
in ice cores from Greenland and Antarctica. The spike indicated a massive
eruption around 1257. The medieval eruption may have sent up to eight times
more sulfate into the stratosphere than the 1883 eruption of Karaktau, often
held up as an archetype of volcanoes behaving badly. Researchers say the 1257
mystery spew is comparable in scope to a second-century AD eruption in the
Taupo Volcanic Zone of New Zealand, known as the most intense historic volcanic
event.
The
1257 eruption had global consequences: Tree-ring records, as well as historical
and archeological sources, show that the Northern Hemisphere experienced
catastrophic floods, crop failures and unseasonable cold the following summer.
A
handful of possible suspects had been investigated, including New Zealand’s
Okataina and Mexico’s El Chicon. One by one, however, they’d been ruled out
through radiocarbon dating or, in the case of Ecuador’s Quilotoa, by comparing
localized deposits with the chemical composition of those found in the polar
ice cores.
Written on Palm Leaves
The
current research zeroed in on Samalas, part of the Mount Rinjani volcanic
complex. One of the researchers’ tips came from Babad Lombok, a
13th century historical record in Old Javanese, written on palm leaves. The
chronicle referenced a massive eruption of Samalas that created an enormous
caldera.
The
team was able to accumulate a sizable amount of incriminating evidence,
including pyroclastic deposits from the eruption more than 100 feet thick found
more than 15 miles from the ruins of the volcano. The range of deposits, and
the volume, suggest that the Samalas eruption exceeded that of the Tambora
event in 1815, another massive volcanic outburst. The team sampled carbonized
tree trunks and branches in the Samalas deposit zone and used radiocarbon
dating to confirm a mid 13th-century eruption.
The
team — which published its findings today in the Proceedings of
the National Academy of Sciences —was also able to match the chemical
composition of pumice deposits from the Samalas eruption with shards found in
both the Antarctic and Greenland ice cores, further evidence that the
Indonesian volcano was the culprit.
Reviewing
wind patterns, researchers were even able to narrow the timeframe for the
eruption. The distribution to the west of volcanic ash and other ejecta from
Samalas suggest that the dry season’s easterly trade winds were prevalent,
putting the eruption window between May and October of 1257.
Perhaps
most tantalizingly, the Babad Lombok notes that the eruption destroyed
Pamatan, what was then the capital of the Lombok kingdom. The researchers
speculate that the ruins of the city may be buried beneath Samalas’ copious
deposits, waiting to be discovered as a “Pompeii of the East.”
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