Note: DO NOT view this video if you have photosensitive epilepsy. It contains rapid lightning flashes.
On April 30th, Indonesia's Ruang volcano released a stunning 1.325 billion metric tons of tephra
as part of a 210 minute long plinian explosive eruption and a shorter 13 minute long vulcanian
eruption.
The tephra from these two combined eruptions reached up to a height of 25.1 kilometers
or 82,349 feet in the atmosphere, and as a result fell across an area of 126,600 square
kilometers or 48,880 square miles.
Yet, while much of the recent focus has been on the areas of land that received ashfall,
I want to note that this only represents a minority of the effected area.
As, while largely out of sight and out of mind, the falling ash did cause a major change
to a section of the Pacific Ocean, causing it to turn bright blue.
The reason?
It triggered a massive but only temporary algal bloom.
The algae was able to quickly utilize the approximately 1,000 parts per million of phosphorus
the andesitic ash contained, causing an explosion in its population.
The same thing occurred due to the April 17th plinian eruption, and in that case caused
a bloom which remained visible from satellite for another 12 days.
Thus, I expect the current bloom to remain visible until around May 11th.
Yet, something else may have occurred in the ocean.
As, a small tsunami with a wave height of a meager 26 centimeters or 10.23 inches struck
on April 30th at 12:28 am which by itself might not seem like much.
However, when you consider that the tsunami had a speed of approximately 293 miles per
hour or 471.5 kilometers per hour, it means that it took 14.6 minutes to reach the distant
buoy sensor, meaning the tsunami originated at around 12:13 am.
This is quite unusual, as this was 137 minutes before the plinian eruption began.
At 12:13 am on April 30th, Ruang was still erupting but it was not actively producing
any pyroclastic flows that were large enough to reach the ocean.
And, looking at the island in its aftermath, there is no evidence that a landslide occurred
either.
Instead, after discussing with several locals what they observed, I believe that a different
culprit is to blame; specifically that a sizable explosion occurred from the same submarine
volcanic vent which popped up only 4 hours before Ruang's plinian April 17th eruption.
My evidence revolves around what the locals heard and saw, as they heard a loud boom around
12:13 am, but when they turned to the Ruang volcano they saw nothing.
This boom was seemingly louder than Ruang's prior explosions, which could mean it occurred
closer to a section of Tagulandang Island than the summit of the Ruang volcano.
If correct, it would not only warrant further investigation but if it were to erupt again
during another period of pressure building underneath Ruang's lava dome, it could indicate
that a major explosive eruption would soon follow from Ruang's summit.
It seems that when the underlying magma chamber reaches an overpressure state that several
hours before it is climactically released, some of the pressure is released through the
aforementioned submarine vent.
And, because this vent could theoretically produce far more powerful explosions, tsunami
hazard models may need to be updated.
As for populated landmasses which received any amount of accumulative ashfall from Ruang's
recent activity, I suggest that groundwater be tested there.
While ash can contaminate groundwater via the addition of numerous heavy metals, the
two most potentially concerning aspects are the presence of fluorine and the overall pH
of the water.
A small amount of added fluorine in water is great for public health but if you get
above 2.5 or especially above 4 parts per million of this element, it can cause fluorosis.
This was the main killer during Iceland's Laki eruption in 1783 to 1784, so I suggest
that groundwater especially on Tagulandang Island be tested to determine if it is currently
safe to drink.
Also, the pH of groundwater should be between 6.5 and 8.5, with a lower figure indicating
possible contamination from sulfur rich compounds in volcanic ash.