UP study of coastal boulders in Ilocos Norte to help disaster preparedness

Geologists from the University of the Philippines Diliman have found traces of extreme waves in large boulders in Pasuquin, Ilocos Norte, that could help coastal communities prepare for similar events in the future.

Edrian Tubalado of UP National Institute of Geological Sciences said analyzing the boulders allows his team to reconstruct past extreme wave events, estimate their intensity, and date their occurrence.

These events include tsunamis and intense storms.

The findings could help local government units and communities strengthen hazard preparedness through better evacuation plans, building codes, and resilient coastal infrastructure.

Tubalado explained the boulders are primarily made of fossilized corals called coastal carbonate boulders.

He said his team measured the boulders’ size, weight, and location, and used specialized dating techniques to determine the ages of the coral components.

“These ages tell us when the coral boulders were transported out from the seawater onto the coast,” Tubalado said.

He added the boulders’ size, such as a 31-ton boulder logged in their study, and weight reveal how powerful the waves were.

The study also revealed that in the town of Pasuquin, waves can reach haround four meters high.

“Our spatial analysis showed that certain areas are more prone to boulder deposition and damage. For example, areas with embayments, or coastal indentations, and steeper nearshore slopes experienced more intense wave energy. This helps identify which areas face the greatest risk,” Tubalado said.

“As climate change potentially increases the intensity of tropical cyclones, understanding the historical baseline of extreme wave events becomes even more critical for predicting future risks and helping coastal communities adapt accordingly,” he added.

The study is titled “Extreme wave events inferred from large subaerial carbonate boulders on a rocky coast in Pasuquin, Ilocos Norte, Philippines.”

It was published in Marine Geology, a journal focused on marine geological processes. —Mariel Celine Serquiña/RF, GMA Integrated News