“Geological Characteristics of Boracay Island”

AN ESSAY BY DAJMAR AMORES

IN the first master plan of the Department of Tourism for Boracay Island, early 1990’s, the geological study of Dr. Punongbayan, former head of philvocs, was included. The recommendations were, however, only half-heartedly implemented if at all. To raise awareness, especially with the ongoing construction boom, the BCCI prints the essay of Dajmar Amores of the Philippine Network of Ecotourism Development (PHILNED), Inc.. Boracay as part of the Philippine archipelago, is part of the ‘ring of fire’, a seismic high active area, stretching from Australia to Siberia and from Alaska to Patagonia.

Early in April 2005, I received an invitation from Department of Tourism (DOT) Boracay field office to the Workshop on Emergency & Security Forum at Casa Pilar. The activity intrigued my interest after seeing Dr. Raymundo R. Punongbayan’s name on the program as one of the resource persons. The former director of the Philippine Institute of Volcanology (PHILVOLCS), was the unassuming geologist who became a celebrity after his outstanding expertise in handling two seismic world-class events - the July 16, 1990 Luzon earthquake and the 1991 Mt. Pinatubo eruptions. Indeed, he was an authoritative icon in his field, in a country where science and technology is hardly appreciated. Unfortunately I lost the chance to meet him personally after the chopper he was flying with crashed in Nueva Ecija, a day short of our scheduled encounter on April 29, 2005. Very few would recall that Dr. Punongbayan was co-author of the mothballed Boracay Master Development Plan where he presented the Geological Characteristics of Boracay Island, an article that featured the physical and geological attributes of the island.

Genesis

Dr. Punongbayan opened his article on the origin of the island, which according to him, was born out of two neighboring islets, with very irregular outline. “As this islets rose slowly and became, emergent, the destructive agents of weathering and erosion started to modify the shape and form of their exposed surfaces.” Looking at the map, it’s easy to accept this theory by looking at the dumbbell shape of Boracay. The elevated area around Yapak and the southern end in Manoc Manoc could be the two islets that dramatically rose to the surface.

Boracay, the next Chocolate Hills?

Boholanons might not like this idea, as the article also projected the Boracay is transforming into chocolate hills. The essay claims that “The more elevated surface of Boracay is rocky and hummocky - a typical feature of areas underlain by coralline limestone layers. With the passage of time, this shall acquire the looks of Chocolate Hills of Bohol.” But here’s a relief for Bohol, the transformation will not occur in our lifetime as the article pointed out, “this shall require a long, long time -- perhaps, about one million years more of continuous action of slightly acidic rain-water which slowly dissolves the carbonate minerals of the coralline layers along exposed surface and downward-going fractures.” In the same chapter, the author estimated the birthdate of the island with less precision, “Since Boracay Island’s landform is still very much unlike Chocolate Hills, then the emergence of Boracay out of Sibuyan must have occurred not a long time ago (-500,000 years ago).”

The famous white sand of Boracay

It was intriguing that a great deal of the presentation focused on the importance of the famous white sands of Boracay. Probably prepared between 1987-1990, Dr. Punongbayan must have noticed that lots of people were collecting sands to adorn aquariums and puka shells were in demand in Manila. It was clear that Dr. Punongbayan tried to underscore this issue as he opened the chapter with, “The most importance geological item in Boracay are the white sandy beach deposits. These are composed of coralline fragments derived thru wave actions from fringing reefs that surround Boracay and from the coralline layers that constitute the island.”

Likewise he corrected the myth that many islanders believe that lumot or seaweed which occasionally appear on the beach, is the eternal source of the famous powdery sand, and thus the apathy towards this issue.

Here’s how those pretty sands are made and how they behave around the island: “Waves would roll, drag and rub these fragment against each other and ultimately deliver the sand-size fraction to the beach zone. Along the beach zone, further wave action would reduce the size and angularity of the coral sands. Longshore currents induce the deposited sandy materials along the southwestern shores of Boracay to migrate towards the northwest when the prevailing winds are from the southwest and those along the northeastern shores to move towards the southeast during the northeast monsoon.’

The point stressed here is the significance of the seasonal movement of the sand particles. Such movement is a natural protection by taming the waves when the winds are strong. Gathering away the sands or any intervention like erecting structures closer to the beach, would not only impede the movement, but natural backlash: “Nor there should man-made structures allowed to be placed orthogonically across the coastline of Boracay to arrest the northwestward and southeastward migration of sandy coralline grains to replace those that were forced by longshore currents to tumble towards the deeper bottom of the Sibuyan Sea.”

Punta Bunga, the area where Club Panoly and Shangri La now stand, were specially mentioned: “The transport of sands by longshore currents also contributes significantly to particle size reduction and this would explain why the beach sand deposit at punta Bunga is relatively fine-grained and almost “powdery”.

Active Faults and Seismicity

On election day, May 10, 2004, while I was casting my vote, I experienced my first tremor in Boracay. It was a strong but curt jolt. However, it was the first time that I’ve heard the horrid sound of an earthquake.

Anyway, that wasn’t at all surprising if we have to agree Dr. Punongbayan’s report along that line:

“There is one active fault (Tablas Fault) whose southwestern segment seems to extend into and transect Boracay Island.

Another active fault quite parallel to it lies to east and about 20 kilometers away. Both faults are deemed active because of the recently recorded earthquakes generated by land displacements occurring along their inferred trace.

Also within the vicinity of Boracay are other earthquake generators like the collisional zones east of Mindoro and Panay Island and many undefined active faults in the sea floor of Sibuyan Sea.”

Although record show that “there were only few earthquakes generated in the recent past which could have affected Boracay with Intensity 5 or higher.”

The volcanologist cited historical accounts of “tsunamigenic earthquakes (1675 Northeastern Mindoro, 1925 Southern Romblon and 1928 Southern Mindoro Earthquakes) which could have impacted the coastal areas of Boracay.

And it is also likely that Boracay may be made to shake and vibrate vigorously by strong earthquakes generated along Tablas Fault and the western section of Mindoro and Panay Island in the very near future.”

Salt Intrusion

Like any other small island, boracays groundwater resources are very vulnerable and unfortunately contaminated in large areas today. Dr. Punongbayan report suggested that fresh water may be tapped from the sandy deposits connecting the northern and southern islets “but this occurs as a thin prism capping the underlying seawater and its vulnerable to salt water intrusion if overdrawn and to pollution by effluents coming from human settlements and resort establishments.”

This chapter also revealed that “ancient sinkholes which may be found in the island (e.g., beneath the proposed golf course), may also yield fresh water whose volume is highly dependent on the dimension and retention capacity of the collapsed caves and caverns,” The chapter was concluded that there may “not be enough fresh water in Boracay depending on the success of the exploration program for it and the manner by which the identified sources are tapped and protected.”

Fifteen years later, during the Boracay Summit in September 2005, Elisea Gozun, former secretary of DENR, reported that as early as 2000, Boracay’s water resources had already exceeded its limit. She also cited a study made by the University of San Carlos showing that there is already a salt-water intrusion around the island.

Gozun: “This is happening already now because the water in the aquifers is receding much faster than it’s natural replenishment.”

Implications and Recommendations

It’s interesting to note that in the concluding paragraph of his presentation, Dr. Punongbayan reiterated and stressed his focus on the preservation of sand and earthquake. “The white sandy materials along the beach zone of Boracay are supplied very slowly by wave actions working mostly on the debris derived from the surrounding fringing reefs. It took sometimes to put them where they are right now and would therefore require an equivalent amount of time to replace them. They may not be replenished at all and forever gone if the suppliers, the fringing reefs, were allowed to be exploited and unprotected for lack of appreciation and recognition of the key role they play in maintaining the fragile equilibrium of Boracay’s coastal zone.”

And: “Mining of the precious Boracay white sands should be permanently and belligerently not permitted,” he concludes. But alas, our famous scientist must be turning over in his grave as smuggling of the precious sand remains unabated, in fact colored and bottled Boracay sands are blatantly sold at souvenir and wedding shops.

Warning on Structures

The last paragraph of Dr. Punongbayans research warns planners, architect and engineers on “the close proximity to earthquake generators in the Philippine Archipelago should require that proper attention be given to the planning, architecture and engineering of all structures to be emplaced on it - especially if one accepts that there may be weak grounds (like surfaces underlain by caves and caverns) that are prone to instantly collapse during the passage of strong seismic waves and that there are low-lying areas vulnerable to the devastating effects of onrushing tsunami.”

Recently, Elisea Gozun, now a member of the Eminent Persons Group (EPG), reiterated this warning during the Boracay Chamber of Commerce and Industry’s (BCCI) general membership meeting.

Like Punongbayan, she clearly described the fragility of the island’s foundations which are largely sand, karst formation and caves, not solid rocks and stressed on the limits of the height of the buildings.

“These formations are prone to collapse and more weight on certain areas would increase the likelihood of an accident to happen,” she pointed out.

Be informed - Be Prepared

Finally, Dr. Punongbayan concluded his thesis with: “While there is no assurance that a strong earthquake or tsunamigenic earthquake may hit Boracay, all investors and developers should be informed about the potential of one occurring in the future. Simply, this is just to avoid being accused of not telling them so.”

Tourism Secretary Joseph ‘Ace’ Durano announced recently the on-going “updating” of the Boracay Master Development Plan. The original DOT master plan was formulated 15 years ago when conditions where far different from today.

No doubt this project is not an easy task and predictably, the implementation component will be strengthened this time. Whatever it is, Dr. Punongbayan’s dissertation is still indisputable.