Mindanao Seabed Uplift
Mindanao 7.8 Magnitude Quake Kills 61, Lifts Seabed, Threatening Marine Ecosystems For Years
Key Points
PHIVOLCS said the Cotabato Trench ‘pushed upward part of the coastlines of Sarangani and Davao Occidental… exposing the bottom of the sea that was originally submerged,’ and it noted that ‘approximately two metres was the mapped uplift.’
The Cotabato Trench is described as lying as close as 50 km (31 miles) off southern Mindanao, and it has been the site of a ‘swarm’ of thousands of mostly small earthquakes recorded in January.
Officials told AFP they could not yet precisely quantify the total affected area because they still needed to survey the site’s full size.
After the quake, residents reported the coastal uplift about two days later, and a dispatched team later found long stretches of shoreline, coral reef and seagrass beds exposed.
Images released by the environment department’s regional office showed a ‘large swathe of exposed coral with dead fish and other aquatic life lying on top,’ underscoring how quickly the ecosystem was laid bare.
A 7.8-magnitude earthquake struck southern Mindanao on June 8, 2026, killing at least 61 people, injuring more than 1,400, and leaving 40 missing, according to Xinhua. The quake also triggered a rare geological event: it shoved the seabed upward by as much as two meters, permanently extending the shoreline by up to 200 meters in parts of Sarangani and Davao Occidental.
When residents walked to the coast two days after the shaking stopped, they found a new landscape — coral reefs, seagrass beds, fish, eels, and clams all lying exposed and dying on what had been the ocean floor. Philstar reported that PHIVOLCS Director Teresito Bacolcol called it the strongest quake to hit the region since the deadly 1976 Moro Gulf disaster.
Seabed Thrust Two Meters Above the Waterline
The Philippine Institute of Volcanology and Seismology (PHIVOLCS) said the Cotabato Trench "pushed upward part of the coastlines of Sarangani and Davao Occidental, exposing the bottom of the sea that was originally submerged," according to Philstar. The trench sits roughly 50 kilometers off the southern Mindanao coast. When the fault ruptured, the overriding plate — the land under Mindanao — snapped upward in seconds.
Officials said the average vertical rise was about two meters, with the shoreline pushing outward by as much as 200 meters in some spots, South China Morning Post reported. Surveyors from PHIVOLCS and the Mines and Geosciences Bureau flew aerial surveys on June 11 to map the full extent. Officials told AFP they still could not precisely measure the total affected area.
Coral Reefs and Fish Left to Die in Tropical Sun
The Department of Environment and Natural Resources released images showing "large swathes of exposed coral with dead fish and other aquatic life lying on top," according to South China Morning Post. Fish, eels, clams, and shells were all found stranded on the newly dry seafloor. As the organic matter began to rot in the heat, residents in Barangay Pangyan reported fears of harmful fumes rising from the decaying mass.
Experts warned the damage to reef and seagrass nurseries — the breeding grounds for Sarangani's fishing industry — could cause fish stocks to collapse for years, Newsy Today reported. Fishermen described the uplift not as a geological marvel but as a wall that had "turned the sea into stone." Boats can no longer reach traditional docking spots now blocked by shallow, exposed reef.
Cotabato Trench Had Already Sent a Warning in January
The Cotabato Trench had been restless all year. In January 2026, PHIVOLCS recorded a "swarm" of thousands of mostly small earthquakes along the same fault zone. Seismologists noted those smaller quakes did not release enough energy to relieve the stress building in the locked section of the trench — which finally gave way on June 8, according to Newsy Today.
By June 14, aftershocks had surpassed 5,200, Philstar reported. A similar uplift happened during the 2013 Bohol earthquake (magnitude 7.2), which raised the shoreline by up to 1.2 meters. The June 2026 event nearly doubled that vertical displacement, making it the largest recorded coastal uplift in Philippine history.
346,000 People Affected as Cleanup Begins
The National Disaster Risk Reduction and Management Council said 346,449 people — about 75,000 families — have been affected. Some 45,000 have been displaced from their homes. Preliminary estimates put infrastructure damage at roughly ₱1 billion, or about $20.3 million, with 54,000 homes damaged or destroyed and 45 road sections and 8 bridges knocked out, according to LinkedIn.
Cleanup of the exposed seafloor is expected to be slow. Officials said the sheer scale of the affected coastline makes it hard to clear decaying marine life quickly. PHIVOLCS said all six of the Philippines' active trenches are now under heightened monitoring, warning that the June 8 rupture may signal growing stress elsewhere along the archipelago's seismic network.
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