Philippine Daily Inquirer

‘World’s largest caldera’ at PH Rise

- —STORY BY FRANCES MANGOSING

The world’s largest caldera may be found underwater at Philippine Rise, according to Filipino marine geophysici­st Jenny Anne Barretto. Her study showed that a crest of the rise has the form of caldera with a diameter of 150 kilometers, much bigger than Yellowston­e’s 60 km. It’s aptly named Apolaki Caldera, or “giant lord,” after the Filipino mythical god of the sun and war.

The world’s largest caldera may be found underwater at Philippine Rise, or Benham Rise, according to a Filipino marine geophysici­st.

According to the study by New Zealand-based scientist Jenny Anne Barretto, along with Ray Wood and John Milson, Benham Rise was formed by volcanic activity between 48.9 million and 42.5 million years ago.

Her study, “Benham Rise unveiled: Morphology and structure of an Eocene large igneous province in the West Philippine Basin,” was published on Sunday by Marine Geology, an internatio­nal journal on marine geology, geochemist­ry and geophysics. It was also made available online on the same day.

‘Apolaki’

Among its key findings are that Benham Rise is a “large igneous province,” or a collection of rocks formed from cooled magma, and that the crest of the rise has the form of a caldera with a diameter of about 150 kilometers. It named the volcanic feature Apolaki Caldera, or “giant lord,” after the Filipino mythical god of the sun and war.

Philippine Rise is a 13-million-hectare undersea plateau off Aurora and Isabela provinces.

The United Nations Commission on the Limits of the Continenta­l Shelf recognized the area in 2012 as part of the Philippine­s’ continenta­l shelf.

In a Facebook post on Monday, the University of the Philippine­s’ Marine Science Institute Geological Oceanograp­hy Laboratory said Benham Rise’s caldera could be the world’s largest.

Comparison­s

“For comparison, Earth’s largest calderas, like the Yellowston­e, is only about 60 km. The size is comparable to shield calderas [on] Mars (Olympus Mons; 80 km x 65 km) and Venus (Sacajawea; 150 x 105 km),” it added.

A caldera is a large cauldronli­ke depression formed after a large volcanic eruption. It is different from a crater, which is a smaller depression.

Taal Lake south of Metro Manila is an example of a caldera. The Taal caldera has 40 craters and is about 25 km wide.

The June 1991 eruption of Mt. Pinatubo, considered by volcanolog­ists the second largest in the 20th century, left a 2-km-wide caldera that later evolved into a lake.

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