In the Know: Behnham Rise

Benham Rise, also known as Benham Plateau, is a seismically active undersea region east of Luzon, off the provinces of Isabela and Aurora.

Formed by intraplate igneous activity, the Benham Rise region spans about 24.4 million hectares—with 11.4 million hectares within the country’s exclusive economic zone and 13 million hectares as extended continental shelf (ECS).

The Benham Rise region, a massive formation of basalt, a common volcanic rock, has been shown to have natural gas deposits and manganese nodules that, according to former Environment Secretary Ramon Paje, is vital in the production of steel.

The underwater geological formation is composed of Benham Rise, Narra Spur and Molave Spur — all constituting a volcanic plateau standing about 3,500 meters above the surrounding seafloor at its crest, and about 500 m  above the surrounding seafloor along its northern and eastern margins.

The shallowest part in Benham Rise, which is less than 50 m deep, is called the Benham Bank.

In an expedition in May  2016, marine scientists observed in Benham Bank a 100-percent coral cover in several sites, with an impressive field of plate corals. They also found a dazzling array of soft and hard corals, fish, algae and sponges.

“We saw terraces of corals as far as the eye could see. It’s so exciting to know that we have such a vast and pristine coral reef ecosystem within Philippine territory,” Marianne Pan-Saniano, a marine scientist at Oceana Philippines, was quoted in the organization’s newsletter in February.

Benham Rise, which is connected to the eastern margin of Luzon through the Palanan and Bicol saddles, is enclosed by the coordinates 119°30’E to 132°00’E and 12°10’N to 20°30’N latitude.

It lies within the continental shelf of the Philippines as defined by the 1982 UN Convention on the Law of the Sea (Unclos).

Under the Unclos, a coastal state’s exclusive economic zone extends 370 kilometers (200 nautical miles) from its continental shelf, while its extended continental shelf (ECS) extends for another 278 km (150 nautical miles).

In 2012, the Commission on the Limits of the Continental Shelf of the United Nations adopted in full the Philippines’ submission for an ECS in the Benham Rise region.

The ECS is a part of the seabed, not including the waters, which holds mineral and genetic resources. The ECS in the Benham Rise region has an area of 135,506 sq km (13.5 million hectares), equivalent to about half of the country’s land area. —Ana Roa, Inquirer Research

Sources: Inquirer Archives, namria.gov.ph, Summary of the Partial Submission of Data and Information on the outer Limits of the Continental Shelf of the Philippines