Biri rock formations declared national geological monument

AWESOME WORK OF NATURE The stunning rock formations in Biri town, Northern Samar, shown here in July 2024, is officially recognized as a national geological monument by the National Committee on Geological Sciences, paving the way for the local government’s bid for recognition by the United Nations Educational, Scientific and Cultural Organization as a global geopark. — Photo courtesy of Rene Castino

TACLOBAN CITY—The famed rock formations in Biri town, Northern Samar, have been officially declared the newest national geological monument (NGM) in the country, marking a major step in Northern Samar’s ongoing bid to secure recognition as a global geopark of the United Nations Educational, Scientific and Cultural Organization (Unesco).

The declaration was received on Tuesday by Northern Samar Rep. Edwin Ongchuan, Gov. Harris Ongchuan and Biri Mayor Antonio de los Reyes Jr. during a ceremony held months after the province launched its global geopark campaign on June 4.

Kevin Garas, supervising geologist of the Mines and Geosciences Bureau (MGB), presented the basis for the declaration and detailed the geological attributes that make the Biri Rock Formations worthy of national distinction, according to Jhon Allen Berbon, head of the Provincial Economic Development and Investment Promotions Office.

Garas highlighted the site’s exceptional scientific importance, uniqueness, and breathtaking beauty, noting that it represents a rare natural archive of Northern Samar’s geological past.

The declaration was made by the National Institute of Geological Sciences (NIGS) which is under the supervision of the MGB.

Supported by extensive research led by Dr. Allan Gil Fernando of the University of the Philippines-NIGS, experts found that the Biri Rocks comprise tilted marine sedimentary sequences of conglomerates, sandstones, siltstones, and shales formed 15 to 20 million years ago.

Distinct features

The formation—sculpted by tectonic uplift and relentless wave erosion—created the iconic seven islets that make up the Biri Rocks landscape.

One of the most distinctive features cited by the National Committee on Geological Sciences is the presence of phonolite and analcime clasts embedded in the sandstone strata—an occurrence rarely documented in the Philippines—which offers deeper insight into the magmatic evolution of alkaline rocks in Northern Samar.

Biri now joins an exclusive list of geological monuments in the Philippines, becoming the newest addition after more than 20 years.

Previous NGM sites include Montalban Gorge in Rizal, Taal Volcano in Batangas, the Ilocos Norte Sand Dunes, the Hundred Islands in Pangasinan, the St. Paul Limestone Formation in Puerto Princesa City, and the Chocolate Hills in Bohol.