Deadly Philippine quake raises seabed by up to two meters, killing coral

A powerful earthquake that killed at least 61 people in the Philippines this week raised the seabed by as much as two meters (6.6 feet), the environment department said Sunday.

The 7.8-magnitude tremor struck southern Mindanao on Monday, leaving at least 40 more people missing, according to the national disaster agency.

What did the Philippine earthquake do to the seabed?

The Mindanao quake triggered a geological phenomenon called coastal uplift, pushing sections of the ocean floor above the waterline.

The seabed rose by approximately two meters in affected areas, extending shorelines by as much as 200 meters in some places. Exposed coral reefs, seagrass beds, and dead marine life were found along the coast two days after the quake.

What caused the coastal uplift in Mindanao?

The Philippine Institute of Volcanology and Seismology attributed the uplift to movement along the Cotabato Trench. The trench lies roughly 50 kilometers off the southern Mindanao coast and is one of the country's most seismically active zones, including a swarm of thousands of small earthquakes recorded there in January.

The shifting of the trench "pushed upward part of the coastlines of Sarangani and Davao Occidental provinces, exposing the bottom of the sea that was originally submerged," the institute said.

What is the environmental damage from the quake's coastal uplift?

A team dispatched to the area found long stretches of exposed shoreline, coral reef, and seagrass beds. Images from the department's regional office showed large sections of dead coral with fish and other aquatic life stranded on top. "These exposed corals and seagrass beds had begun dying off alongside their resident organisms such as reef fishes, eels, clams, and shells," the environment department said.

Residents first reported changes to the seabed out of concern that fumes from decaying sea life could poison them. Officials said they could not yet determine the full extent of the affected area given its size. A complete survey remains ongoing.