*Mt Pinatubo and the Kapampangan region before 1991*

/This a copy of a paper published in the issue XVI of K Magazine./

The present article is a reply to the paper entitled “How the volcano
reclaimed Pampanga from the sea” published in Vol. 2 No. 2 of Singsing
magazine (pp. 46-49). Indeed, the fiction scenario on the role of Mt
Pinatubo in present-day Pampanga geological history and early human
occupation suggested in the said paper requires some comments and
corrections.

The following discussion is based on an on-going multidisciplinary study
intended to reconstruct the eruptive dynamism, environmental
consequences and human implications of the 800-500 ybp eruption of Mt
Pinatubo called Buag eruptive period. This project involves Franciso G.
Delfin Jr. (School of Policy, Planning & Development - University of
Southern California, USA), Eusebio Z. Dizon (Archaeology Division -
National Museum of the Philippines), Victor J. Paz (Archaeological
Studies Program – University of the Philippines Diliman), Emmanuel G.
Ramos (Manila Observatory), Cristina T. Remotigue (National Institute of
Geological Sciences, University of the Philippines Diliman), Kelvin S.
Rodolfo (Department of Earth and Environmental Sciences - University of
Illinois at Chicago, USA / National Institute of Geological Sciences,
University of the Philippines Diliman), Fernando P. Siringan (National
Institute of Geological Sciences, University of the Philippines
Diliman), Leah A. Soria (National Institute of Geological Sciences,
University of the Philippines Diliman), Jesse V. Umbal (BMP Environment
and Community Care Inc) and Jean-Christophe Gaillard (Department of
Geography – University of the Philippines Diliman / Institut de
Géographie Alpine – Université Joseph Fourier Grenoble I, France). The
state of our present knowledge will be published during the second
semester of 2005 (Gaillard et al. forthcoming). A shorter, archaeology
and geography oriented version of this paper has however already been
published in the Philippines (Gaillard et al. 2004). The scope of this
project goes far beyond the allegation of the Singsing paper (p.47 §1).

This being said, let me correct first some of the most obvious baseless
assertions of the Singsing article.

1/ Chronology of the events: The paper does not work on any clear
chronology regarding land reclamation. Such discomfort from the
author(s) is actually rooted in the lack of existing data regarding
pre-1991 Mt Pinatubo. As indicated in the Singsing paper, our present
sketchy knowledge about modern Pinatubo only indicates six eruptive
periods before the 1991 explosion (e.g. Newhall et al 1996). This
six-period chronology is based on geological data retrieved from the
slopes of Mt Pinatubo only. There is no study yet regarding the
environmental implications for the surrounding lowlands of the events
that occurred before 1800 ybp. Our knowledge is even sparser regarding
the human consequences of pre-800-500 ybp events. Any allegation on what
happened before 1800-800 ybp is therefore pure guess work.

3/ Sea level receding (all along the paper): The sea level has not been
receding continuously since 35,000 years ago! It retreated up to 18,000
ybp only, the last glacial maxima of the Pleistocene period, before
quickly rising until 6,000 ybp to its present level (e.g. Chappell and
Thom 1977 or Belwood 1997). The whole demonstration of the manuscript
regarding the progressive exposure of the Central Luzon Basin during the
last few millenniums (we do not know at what rate and along what time
frame since the paper does not give any data) therefore collapses.

4/ Arrival of the first settlers (p. 47 §2): As of now, there is no
archaeological, anthropological, genetic, botanical or linguistic proofs
to make any claim regarding the exact time and the route of arrival of
the first settlers in the Kapampangan region (for both Negritos and
Austronesian speakers). The general pattern for the peopling of Island
Southeast Asia as a whole is still debated (e.g. Gaillard and Mallari
2004). Therefore, how can serious hypotheses at the Kapampangan region
scale be drawn? Mentioning early settlements on the slopes of Mt Arayat
is pure guess work too. There is absolutely no archaeological evidence
for such allegations so far. It is as well awkward to use the 5,000 ybp
so-called Candaba adze as proof of early settlement in the Kapampangan
region since this artefact was a surface find without any secure
geological context. This may have been brought in the Candaba area by
flood waters.

5/ The route of the Pampanga River (p. 48-49 §2-3-5-6): The Singsing
article asserts that the Pampanga River has been “pushed behind Mt
Arayat” from its original route on the west side. Where are the data to
support such hypothesis? Seriously and once again, there is no data
regarding the evolution of the Pampanga River and no claim can be made
regarding possible evolution of its course.

6/ Early settlements in the Candaba swamp (p. 48 §3): If it is true that
artefacts (notably earthenware, stoneware and ceramic sherds) have been
retrieved from the swamp, these were surface finds out of their
geological context. It is therefore much too early to draw any
conclusion regarding early settlements in this area. Proper
archaeological excavations still need to be conducted.

7/ Last 400 years (p. 49 §5): It is asserted that lahars continued to
alter the landscape of the region, then pushed the Pampanga River behind
Mt Arayat and reclaimed the Masantol area. If such important events
occurred during the Spanish period, it is most likely that the
conquistadors would have documented them. But there is no written
account of lahars in Spanish documents! Lahars have stopped before 1571
and the 400 ybp shoreline was probably very close to the present
coastline. Moreover, the present-day Masantol area only receives a small
fraction of Pinatubo material. Indeed, the Sacobia River is the only one
river coming from the volcano slopes that empties in the Pampanga River
which passes through Masantol. Of course, this may have been different
in the past but geomorphic data indicates that the Guagua-Lubao-Sasmuan
area is the sector likely to have been reclaimed on the sea during the
Buag eruptive period, not the Masantol-Macabebe area.

9/ Moriones and O’Donnell rivers (p. 49 §6): For the information of the
author(s), these two rivers are part of the Agno River basin and flow
northward to the Lingayen Gulf, not southward to the Pampanga River…

10/ Lahars and subsidence (p. 49 §6): Lahars should be seen as a natural
counterbalance to natural or man-enhanced delta subsidence. The main
catalyst of natural delta subsidence in our present days is the
continuously increasing pumpage of groundwater for domestic purposes
(Siringan and Rodolfo 2003). This has nothing to do with Mt Pinatubo but
with the increasing demand for water induced by the fast population growth.

Following these series of comments on the Singsing paper, I would like
now to share our modest knowledge about the impact of the 800-500 ybp
eruption of Mt Pinatubo in the present-day Kapampangan region. Our study
about the Buag eruptive period of Mt Pinatubo consists in assembling and
piecing evidence from archaeology, local legends, and toponymic trends
to supplement geological and geomorphic data. This correlation of data
enables us to suggest a tripartite synthesis of the Buag eruptive
period: First, an initial Plinian eruption with widespread tephra falls
and accompanying pyroclastic flows and lahars close to the volcano;
next, the extrusion and growth of a dome, and, finally, collapse of part
of the growing dome that generated the youngest, distinctive ash flow
sheet filling the Marella valley. The lahars of the second phase
gradually became more normal, rain-induced sedimentation that continued
through and beyond the third phase, slowly filling in the shallow bays
in Pampanga and Zambales. On a geologic time scale, all three can be
treated as contemporaneous, but the opening Plinian eruption may have
preceded the second and third phases by years, decades or even centuries.

The early Plinian phase of the Buag event ejected a vertical eruption
column and spread ash far and wide, while smaller but possibly numerous
pyroclastic-flows carried larger volcanic materials along or near the
headwaters of the major Pinatubo tributaries. This Plinian eruption
likely left a small summit depression comparable to that produced by the
1991 eruptions. Lahars remobilized pyroclastic materials deposited on
the flanks of the volcano in most of the watersheds draining Mt.
Pinatubo (except Gumain and Porac). Far-reaching lahars may have filled
a “proto Pampanga bay” extending from present Manila Bay northward into
Bacolor. A sediment core acquired in San Rafael Baruya, Lubao, Pampanga,
indeed contains a 2 cm thick layer of pumiceous sand at a depth of 8.4 m
in shallow marine deposits. These pumiceous materials are the uppermost
sandy deposits below the layer associated with the 1991 eruption and
were thus expected to be of Buag age. Wood samples from immediately
below and above the sandy layer have recently been dated at 1802 and
1670 y BP (radio carbon samples WW-4685 and WW-4686). These dates are
too old to be of Buag age and too young to be of Maraunot age. However,
it is unknown if the wood samples were in-situ or had been reworked.
This limitation opens the door to two interpretations. If the wood
samples were in-situ, the 1730 and 1800 y BP dates may reflect a still
undocumented eruptive event of Mt. Pinatubo. Conversely, if the pieces
of wood were reworked, the pumiceous layer may indeed be associated with
the Buag event and only contains transported and older wood fragments.
Given that the sandy layer reflects a near-shore environment, it
suggests that present day Lubao was submerged as late as 500 y BP or
1800 y BP. The early, Plinian phase of the Buag period is well retained
in both oral history and toponymy. The best account is the Ayta legend
about how the supernatural spirits Blit and Aglao fought a turtle that
scaled the summit, dug a hole, howled loudly and breathed fire, shaking
the earth. In Bacolor, Mexico, and Conception, villages named ‘Balas’,
which means ‘sand’ in Kapampangan, may also suggest memories of lahars
or pyroclastic-affected lands in the fairly recent past. That the Porac
river valley was not inundated by a major pyroclastic flow during the
latest event is also consistent with only a tephra fall layer recorded
in the Babo Balukbuk archaeological site, which contains ceramics of the
appropriate cultural age range of the 13th to 16th centuries and pieces
of charcoal recently dated at 506 and 486 ybp (samples WW-4683 and
WW-4684). Despite the uncertainty regarding the wood samples recently
dated at 1670-1802 ybp (samples WW-4685 and WW-4686), the Lubao-Bacolor
area very likely was a shallow northward extension of Manila Bay until
filled in with pre-Buag or early Buag-period sediment. This is further
indicated by the toponym ‘Uaua,’ meaning ‘river mouth’, 15 km inland
from the current shore.

In a second time, following caldera collapse, a 2 km-wide andesite dome
grew filling the crater. This event formed the steep-sided 2 km-wide
dome characterizing the pre-1991 summit of Mt. Pinatubo. The extrusion
and growth of the pre-1991 Pinatubo summit dome did not leave
substantial marks in the sedimentologic or in the archaeological record,
probably because this activity was confined to the summit area. However,
it may have been witnessed by Ayta people as suggested by the name
‘Pinatubo’.

In a third stage, a portion of this dome collapsed and generated
pyroclastic flows in the southwestern slopes of the volcano. These
pyroclastic materials partially filled the upper-Marella and Santo Tomas
River valleys. This last event is the most well-constrained event of the
Buag eruptive period. At least two dates from the Marella valley (one
from the Buag archaeological site, and one downstream suggest calibrated
calendar dates ranging from 476-545 yr BP (samples WW-111 et W-6509).
This would put the event sometime in the early- to mid-15th century,
which is consistent with the ages of Chinese and Anamese ceramics found
at Buag. The destruction of the old Buag settlement following the
partial collapse of the dome may also be retained in the toponym ‘Buag’
which means ‘to collapse over’ or ‘to pill over’ in surrounding languages.

The Buag eruptions would have triggered a general redistribution of the
population from the foothills of the volcano toward the delta plains if
this had been reclaimed downstream by lahar deposition. This is
underlined by the archaeological and toponymic records on the eastern
side of Mt Pinatubo, and the early Spanish chronicles in the late 16th
century. The Spaniards described many densely populated riverbanks in
the Pampanga River delta, within a triangle extending from Macabebe and
Lubao to Betis or ‘Vitis’, now part of Guagua (Blair and Robertson
1903-09; de San Agustin 1998). Some fortified settlements had a few
thousand people, notably Betis with 7,000 inhabitants and Macabebe with
2,600 (Jocano 1975). If this area was reclaimed by pre-Buag or Buag
lahars, these settlements must have been established well before the
Spaniards arrived, after the last Buag eruptions that affected the
southeast sector of the volcano. The Buag eruptions must have
drastically redistributed any population southward away from the
volcano. Indeed, Spanish chroniclers reported at the end of the 16th
century that populations near Mt Pinatubo were very sparse. Some local
place names in this upper region (Balas, Sapang Bato), however, may
reflect oral memory of the Buag eruption. The foothills of Mt. Pinatubo
have also yielded several archaeological sites in Sitios Babo Balukbuk
and Gubat in Porac.

Finally, during the Buag eruption period, the slopes and surroundings of
Mt Pinatubo most probably were inhabited by three major ethno-linguistic
groups. On the east side, the Kapampangans occupied the southwestern
part of the Luzon central plain. Early Spanish accounts (Blair and
Robertson 1903-09) suggest that the narrow coastal plain of Zambales,
and possibly also inland Pampanga were inhabited by Sambals, which are
nowadays divided into Sambal Tina and Sambal Botolan. Finally, the Aytas
inhabited the east and west flanks of the volcano. Indeed, only these
three groups preserve traces of the prehistoric eruption in their local
legends.

This sketchy reconstruction of the 800-500 Mt Pinatubo constitutes the
rough limit of our present knowledge of this event. More details can be
found in the publications above mentioned (Gaillard et al. 2004;
Gaillard et al. forthcoming). The purpose of this reply article is to
prevent the spread of new myths (there are already so many) regarding
the Kapampangan region geological history and early human occupation.


References

Bellwood, P., 1997, Prehistory of the Indo-Malaysian archipelago.
Academic Press: Sydney.

Blair, E.H. and Robertson, J.A. (eds), 1903-09, The Philippine Islands
1493-1898, Arthur H. Clark: Cleveland, 55 volumes.

Chappell, J. and Thom, B.G., 1977, Sea Levels and Coasts. In Allen, J.,
Golson, J., Jones, R. (eds), Sunda and Sahul: Prehistoric Studies in
Southeast Asia, Melanesia and Australia. Academic Press: London, 275-291.

de San Agustin, G., 1998, Conquistas de las Islas Filipinas (1565-1615),
San Agustin Museum: Manila.

Gaillard, J-C. and Mallari, J.P., 2004, The peopling of the Philippines:
A cartographic synthesis. Hukay: Journal of the University of the
Philippines Archaeological Studies Program, 6, 1-27.

Gaillard, J-C, Delfin Jr, F G, Dizon, E.Z., Paz, V.J, Ramos, E.G.,
Remotigue, C.T., Rodolfo, K.S., Siringan, F., Soria, J.L.A., Umbal,
J.V., Forthcoming, A reconstruction of the ca. 800-500 BP. Buag eruption
of Mt. Pinatubo, Philippines. In Grattan, J., Torrence, R. (eds.),
Living under the shadow: The archaeological, cultural and environmental
impact of volcanic eruptions. University College London Press: London.

Gaillard, J-C., Delfin Jr., F.G., Dizon, E.Z., Paz, V.J, Ramos, E.G.,
Remotigue, C.T., Rodolfo, K.S., Siringan, F., Soria, J.L.A., Umbal,
J.V., 2004, Socio-economic impact of the c. 500 yr BP eruption of Mt.
Pinatubo (Philippines): Hypotheses from the archaeological and
geographical records. Proceedings of the Society of Philippine
Archaeologists, 2, 46-58.

Jocano, F.L., 1975,The Philippines at the Spanish Contact, MCS
Enterprises Inc: Manila.

Newhall, C.G., Daag, A.S., Delfin Jr., F.J., Hoblitt, R.P., McGeehin,
J., Pallister, J.S., Regalado, M.T.M., Rubin, M., Tubianosa, B.S.,
Tamayo Jr., R.A., Umbal, J.V., 1996, Eruptive history of Mount Pinatubo.
In Newhall, C G, Punongbayan, R S (eds.), Fire and Mud: Eruption and
Lahars of Mount Pinatubo, Philippines, University of Washington Press
and Phivolcs Press: Seattle and Quezon City, 165-195.

Siringan, F.P. and Rodolfo, K.S., 2003, Relative sealevel changes and
worsening floods in the western Pampanga delta: Causes and some possible
mitigation measures. Science Diliman, 15(2), 1-12.


--
Jean-Christophe Gaillard, Ph.D.
Maître de Conférences
Institut de Géographie Alpine
Université Joseph Fourier - Grenoble I
14 bis avenue Marie Reynoard
38100 Grenoble
France

Tel.: (00)-(33)-(0)4-76-82-20-79
Tel. Phil.: (00)-(63)-(0)919-866-0835
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Email: Jean-Christophe.Gaillard@...