UP-MSI scientists map submarine volcanoes, unmapped Palawan faults, and identify strong OTEC potential in Philippine waters.
Beneath the waves of the Sulu Sea, Celebes Sea, and southern Philippine Sea, Filipino scientists have uncovered a world of hidden volcanoes, unmapped faults, and even potential sources of clean energy.
Researchers from the University of the Philippines-Marine Science Institute (UP-MSI) revealed the findings following a December 2025 deep-sea expedition. They conducted the expedition in collaboration with partners from the University of California, Santa Cruz and Mindanao State University–Naawan.
Using advanced sonar systems aboard the research vessel R/V Thomas G. Thompson, the team produced high-resolution maps of the ocean floor — including features never before documented in detail.
Hidden submarine volcanoes
In the Sulu Sea, scientists detected a 30-meter vertical anomaly above a volcanic structure, likely caused by hydrothermal gases escaping from beneath the seabed.
South of Balut Island in the Celebes Sea, another volcanic feature showed a caldera-like structure — a massive depression formed after a volcanic eruption.
These underwater volcanoes aren’t just geological curiosities. According to UP-MSI geological oceanographer Dr. Fernando Siringan, areas with gas and hydrocarbon seeps often host unique marine ecosystems.
Earlier deep-sea surveys at the Philippine Rise documented sea stars, sea lilies, and rare corals thriving at depths of around 1,300 meters.
Unmapped faults off Palawan
Palawan has long been considered one of the country’s most tectonically stable regions. But the expedition revealed several previously unmapped fault structures off its eastern coast.
One fault along the continental slope shows a 10-meter seabed displacement. Multiple faults were also identified along the projected extension of the Ulugan Bay Fault.
The Philippine Institute of Volcanology and Seismology had earlier linked a magnitude 5.1 earthquake in Palawan on June 11, 2024 to a known fault in the area.
With Palawan being considered as a possible site for a nuclear power facility, researchers are now calling for a reassessment of the province’s geology.
Clean energy from the ocean?
In the southern Philippine Sea, scientists also documented a strong temperature difference — at least 20°C — between warm surface waters and colder deep waters at a depth of just 200 meters.
That temperature gap meets the requirements for Ocean Thermal Energy Conversion (OTEC), a technology that generates electricity using the difference between surface and deep-sea temperatures.
UP-MSI physical oceanographer Dr. Charina Lyn Amedo-Repollo said the findings suggest high potential for continuous baseload renewable energy, with possible applications for desalination and seawater cooling.
The expedition also recorded interactions between the Mindanao Current and Mindanao Undercurrent, generating internal waves that help bring nutrients to the surface — supporting fisheries and marine ecosystems.
Why this matters
Despite being surrounded by some of the world’s deepest waters, much of the Philippines’ marine environment remains underexplored.
The mission — funded by the United States Office of Naval Research — marked the first time water samples were collected from 5,200 meters deep in the Celebes Sea.
The message is clear for policymakers: the country’s deep seas hold both risks and opportunities — from seismic hazards to renewable energy and blue economy growth.
As Amedo-Repollo put it: “We don’t only see water. We see opportunities for future work.”
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