Within Indonesia is a very unique volcano which you may own a piece of right now without
even knowing it.
At this volcano, named Mount Papandayan, an entire flank its hydrothermally altered to
bright shades of yellow, orange, and white.
Within this flank are banded layers of calcite which contain the arsenic mineral realgar
along with finely grained black pyrite.
This material has since been widely sold as a gemstone and is known as bumblebee jasper.
However, the reason why all of this beautiful material has been exposed relates to a much
darker part of this volcano's history.
In 1772, a large section of Mount Papandayan collapsed in what was one of the planet's
deadliest volcanic eruptions.
This collapse revealed a section of rock which would have otherwise remained several hundred
meters underground.
Although Papandayan has not produced a major volcanic eruption since, this volcano is still
quite dangerous due to its habit of producing intermittent phreatic eruptions which often
occur without warning.
The Mount Papandayan stratovolcano is located in central Indonesia on the island of Java,
where it is 155 kilometers southeast of the city of Jakarta.
Although its true age is unknown, this volcano appears to be less than 50,000 years old based
on the level of erosion present.
Based on this estimate, the Papandayan volcano began forming around 38,000 years ago, when
a dike of andesite composition magma intruded into the crust.
This dike eventually reached the surface where it erupted at several vents along a northeast
trending orientation.
As the medium silica content magma interacted with the area's abundant groundwater, it generated
a series of large explosions which formed several small craters in the ground.
Eventually, subsequent eruptions began consolidating in a single volcanic cone.
This cone produced explosive eruptions, during which lobes of gray andesite lava would flow
several kilometers from its summit.
These vulcanian eruptions occurred several dozen times, leading to the creation of a
typical looking gray stratovolcano much like Merapi.
However, the northeastern flank of Papandayan was not colored gray but instead turned shades
of red, yellow, and white.
The underlying dike geometry remained, meaning that whenever new magma intruded into the
crust, much of its volcanic gasses were funneled into the northeastern flank of the volcano.
Over time, these gasses destabilized the overlying rock, as strong minerals were replaced with
easily eroded counterparts.
After several thousand years of hydrothermal alteration, an entire flank of this volcano
became unstable.
Then, in 1772, a large body of magma once again intruded into this volcano.
This pushed the overlying rock upwards by several meters, further decreasing its stability.
Then, a powerful eruption broke through the surface.
As a large explosion sent ash high into the atmosphere, the entire northeastern flank
of Papandayan began to collapse.
In the span of 2 minutes, 140 million cubic meters of rock slid up to 11 kilometers distant
from the volcano.
Once the collapse had ended, pyroclastic flows raced down the newly breached crater.
In total, 32 square kilometers of land, along with 40 villages were completely buried in
highly altered volcanic rock.
This landslide removed the top 50 meters of the volcano over a large area, which exposed
the arsenic rich carbonate rock which today bumblebee jasper is mined from.
While this collapse may seem like an isolated event, the shape of the volcano suggests that
it was not.
Based on the existence of 5 other large collapse scarps on its edifice, similar large volume
landslides appear to repeat about once every 4000 years.
Thus, because this volcano has a history of violently collapsing to the northeast, it
will once again collapse in that direction in the future.
From 1923 to 1925, and then again in 1942, small phreatic explosions occurred within
the recent collapse scar which formed decently sized craters.
Then, in 2002, Papandayan erupted again as magma was ejected onto its surface.
From this same vent later emerged a series of pyroclastic flows, which traveled 2 kilometers
downslope, wiping out all vegetation in their path.
This same eruption triggered a smaller landslide from hydrothermally altered rock, which destroyed
several structures.
In conclusion, whenever Papandayan erupts, it is not safe to be within 10 kilometers
downslope of its northeastern edifice.
A large portion of the volcano could collapse without warning, and there would be no escaping
such a landslide.
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