Monday, November 26, 2012

Insights from the Other Side of Yesterday

“He climbed the Mount Pinatubu in exactly twenty-one tremendous leaps. When he had reached the top, he at once began to dig a big hole into the mountain. Big pieces of rock, mud, dust, and other things began to fall in the showers around the mountain. During all the while, he howled and howled so loudly that the earth shook ... The fire that escaped from his mouth became so thick and so hot that the pursuing party had to turn away.”
Mount Pinatubo on June 15, 1991.  From USGS / Cascade Volcano Observatory
Mount Pinatubo is a stratovolcano on Luzon Island in the Philippines, part of a volcanic chain along the Manila Trench where the Sunda Plate (southeast Asia) is being subducted under the Philippine Mobile Belt.  Pinatubo sits -- perhaps hides -- in the midst of heavily-vegetated non-volcanic mountains, and was known to few geologists prior to 1991.  Then on June 15, it exploded, producing the second largest terrestrial volcanic eruption of the century.  Compounding the disaster, Luzon was hit by Typhoon Yunya on the same day.
Snow-like deposits of rain-soaked ash and debris.  USGS photo (R.P. Hoblitt).
The immensity of the eruption was a horrible surprise, but it didn't come without warning. There had been many small earthquakes around Pinatubo, several steam explosions, and increasing emissions of sulfur dioxide gas during the preceding months.  In early June, the first magma reached the surface, as lava flows.  Then on June 12, gas-charged magma exploded from the volcano.  Dramatic eruptions continued for the next few days, but these were only Pinatubo's opening acts.  On June 15, truly cataclysmic activity commenced. Huge ash columns reached as high as 40 km, and avalanches of pyroclastic debris raced down the volcano's slopes at 70-80 kph, burning everything.  During the largest explosions, incandescent avalanches traveled as far as 16 km from the mountain.  Nineteen major eruptions were registered that day before recording stopped.

By the time things had quieted down several days later, more than a cubic mile (5 cubic km) of material had been ejected and Pinatubo had collapsed, forming a caldera 2.5 km across and over 600 m deep.  The high point of the rim -- and the mountain -- was 260 m lower than the original summit.
Pinatubo caldera.  Ash continued to vent from the floor through late June and July.  USGS photo (J. Mori).
“On the summit of the Pinatubu was the great hole, through which Bacobaco had passed, and from which smoke could be seen constantly coming out. This showed that although he was already quiet he was still full of anger, since fire continued to come from his mouth...”
Bacobaco -- “the terrible spirit of the sea, who makes the storms and the waves” -- loves deer meat.  He occasionally makes himself into a giant turtle and comes ashore to hunt. 
Pinatubo’s early warnings gave residents time to evacuate, saving at least 5000 lives (USGS 2005a), but much of the destruction came later when extensive deposits of volcanic debris were mobilized by monsoon rains.  For the next five years, lahars (volcanic debris flows) swept down the mountain's major drainages, completely destroying some towns, greatly damaging others.  Lahars dammed tributaries along the way, creating ponds and lakes.  Most impoundments subsequently overflowed, causing even greater destruction.  Losses caused by Pinatubo were estimated at a billion dollars (USA).  Over a million people were displaced.
Pinatubo lahars; from USGS 2005b.
“newly formed Mapanuepe Lake after sinking three villages in San Marcelino, Zambales, Philippines.” (1992)
One of the largest lahar impoundments still exists -- Mapanuepe Lake (above).  There's evidence of an older lake at this site as well, apparently destroyed by a “prehistoric” eruption of Pinatubo (Rodolfo and Umbal 2008).

“For three days the turtle continued to burrow itself, throwing rocks, mud, ashes, and thundering away all the time in [a] deafening roar.  At the end of the three days he stopped, and all was quiet again in the mountain.  But the lake, with its clear water was now filled with rocks, and mud covered everything.”

The aboriginal Ayta people were the ones hardest hit by Pinatubo’s eruptions and terrifying lahars.  Though they had no experience or memory of volcanism, the mountain’s name suggests that perhaps their ancestors had witnessed one of its brutal outbursts.  In the Ayta language, as well as in Tagalog (Filipino), “tubo” refers to growth, and “pinatubo” can be interpreted as “made to grow” or “allowed to grow” (Rodolfo and Umbal 2008).

Prior to the 1991 eruption, Pinatubo's violent past was a secret.  It had kept its fierce personality well-hidden for as long as anyone could remember ... or so people thought.  As it turned out, there had been a report of the hideous monster-nature of Pinatubo, quite a graphic account actually, but it came from the other side of yesterday, a source given little credence in today’s world.

The Pohnpeian people of Micronesia have a term “keilahn aio” which translates to “the other side of yesterday” (Sacks 1997).  It refers to times and events now known only as legend -- things that happened far back, beyond the reach of history.  These things may be myth and legend now, but perhaps they also are remnants of actual events.  Perhaps they are like the memories of early childhood, with little detail beyond a few vivid images.

In 1915, before any geologist knew of the volcanic nature of Pinatubo, J.N. Rodriquez collected and transcribed The origin of Pinatubu volcano (a Negrito myth) from an Ayta storyteller (Rodolfo and Umbal 2008).  Many years ago, Bacobaco, the evil spirit of the seas, had again morphed into a giant turtle and come ashore to hunt deer, his favorite food.  The Spirit Hunters were angry that he was back, and their king, Aglao, consulted with Wasi, the spirit of the wind, as to how to kill the monster, covered as he was with a giant shield on his back.  Wasi whispered to him, “Why don't you ask Blit, my brother, to help you?  He is the only one capable of killing Bacobaco, for if he hits him with the tip of his tail or a toe of one of his feet, it will kill Bacobaco.”

Blit, Aglao and the other Spirit Hunters pursued the giant turtle, shooting arrows at him.  As recounted above, Bacobaco jumped into the lake at the foot of Pinatubo, but the water was so clear that it afforded no protection.  He then bounded to the summit and started to dig -- throwing debris into the sky, obliterating the lake, and breathing fire and smoke from the giant hole he had made for himself at the top of the mountain.

When the Ayta had finished telling the story of Pinatubo, he added his own thoughts:
“But now, you do not see smoke coming out of the Pinatubo mountain ... and many believe that the terrible monster is already dead; but I think that he is just resting after his exertions, and that someday he will surely come out of his hiding place again”
The man was right -- Bacobaco emerged from his hiding place just 76 years later.

Bacobaco came out of hiding on June 12, 1991.  This early eruption was spectacular, but was nothing compared to the climactic explosions that came three days later.  View from Clark Air Force Base.

Sources (in addition to links in post)

Illustrations of Bacobaco were created with designs from Free Tattoo Designs.

ABS-CBN Broadcasting Corporation.  1996.  Pinatubo Volcano “The Sleeping Giant Awakens”

Oppenheimer, C.  2011.  Eruptions that shook the world.  Cambridge Univ. Press.

Rodolfo, K.S. and Umbal, J.V.  2008.  A prehistoric lahar-dammed lake and eruption of Mount Pinatubo described in a Philippine aborigine legend.  J. Volcanology & Geothermal Res. 176:432-437.

Sacks, O.  1997.  The Island of the Colorblind.  NY: Alfred A. Knopf.

US Geological Survey.  2005a.  The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines.  USGS Fact Sheet 113-97.

US Geological Survey.  2005b.  Lahars of Mount Pinatubo, Philippines.  USGS Fact Sheet 114-97.  Online Version 1.1


  1. Replies
    1. Thanks, Lucy, that's very kind. I have to say - this post wrote itself in some ways ... helped anyway, thanks to a fortuitous combination of recent readings. Nice when that happens :)