Philippine Earthquakes and Benham Rise, the World’s Largest Caldera -Should We Be Afraid?

Benham Rise, the world’s largest caldera discovered in the Philippines- does it pose a threat after successive Mindanao earthquakes?

Series of Strong Quakes

The recent successive earthquake incidents in Mindanao had shaken not just the affected areas but the entire country as well. This made us all worry about our safety, particularly the people in the Philippines’ second-largest island group. Some may ask, “Is this a warning?” while others worry, “Are we nearing the end?”

While these may perhaps sound too paranoid, we can’t blame them. We can’t deny the fact the Philippines is geographically located along a typhoon belt – the reason why we get lambasted by quite a number of typhoons each year, plus, we are tagged to be in what they call the “Ring of Fire” where devastating earthquakes and volcanic eruptions take place. Sometimes, we can’t help but shake our heads in disappointment. 

On October 16, 2019, a 6.3 magnitude first struck several provinces in Mindanao, including Cotabato, Davao del Sur, and nearby areas. At 8pm on the same day, the largest aftershock hit with a magnitude of 5.5. Fast forward to October 29, 2019, at around 9am, another quake hit the same area particularly 22 kilometers of Tulunan, Cotabato.

The aftershock hit at around 10:40am about 13 kilometers from the same area. When everyone thought enough was enough, another strong quake hit Tulunan, Cotabato at magnitude 6.5 on October 31 at around 9 in the morning.

The National Disaster Risk Reduction and Management Council (NDRRMC) on November 2 reported at least 17 people dead during the said calamities. According to the Philippine Institute of Volcanology and Seismology (PHIVOLCS), they are looking closely at the possibilities of how the successive strong quakes are interconnected.

But this isn’t the only thing that worries the Filipinos. In a recent report, it was revealed that the world’s biggest caldera is located in the Philippines.  What does this mean? Is this a threat to the country?

Caldera and Its Difference to Crater

A caldera is like an enormously sized cauldron (not the leaky cauldron you’ve seen and heard in the Harry Potter series *wink!) forming after the magma chamber is emptied in a certain volcanic eruption. However, its formation only happens after a large eruption of lava or magma as it leaves a massive spacious hollow.

Can you imagine when something explodes on land, and it leaves a hollow? Think of the ultimate superlative of that aftermath, and you’ll get to imagine how gigantic a caldera can be.

A volcanic crater, on the other hand, is what they call a vent during volcanic activities. It serves as the passage or outlet. Actually, large volcanoes are born when magma, among others, streams out from the said vent. Soon as it does, it builds up a cone around the passage. And when more pyroclastic materials like ash, lapili, and lava blocks among others are ejected from a vent after several eruptions, it starts to form a mountain.

So the difference between the two is that a Caldera is the aftermath, while a Crater is part of the origin of every volcanic eruption.

The Discovery of the World’s Largest Caldera in Benham Rise

The Yellowstone Caldera located in Yellowstone National Park, northwest of Wyoming, U.S. measures 60km in diameter had been known to be an aftermath of a supervolcanic eruption (more than 600,000 years ago). The said National Park is situated over a supervolcano that may possibly erupt at magnitude 8, according to Britannica.

The first eruption, however, had been more than 2 million years ago, where more than 5,000 square miles were covered in ash, while the second was about less than a million years. Despite the length of time, we all can’t help but ask, when will its next eruption shake the world again? How destructive will it be?

According to the National Park Service (NPS) of Wyoming, the said supervolcano may erupt again in the next thousands to million years with slow lava flows, which is enough to secure people. It also adds that no scientific study supports such a catastrophe happening soon.

Thinking that it is in the Yellowstone National Park that the largest caldera is located, a recent study begs to disagree. The world’s largest caldera had been discovered in Benham Rise, an underwater plateau, also known as the Philippine Rise.

Among the team of marine geophysicists who discovered the world’s largest caldera now named “Apolaki” (Filipino Mythical God of the Sun and War) is a New Zealand-based Filipina cum University of the Philippines graduate, Jenny Anne Barreto. The said team has recently published a paper entitled “Benham Rise unveiled: Morphology and structure of an Eocene large igneous province in the West Philippine Basin,” revealing the said caldera that measures 150 kilometers in diameter. Yes, it doubles the size of the Yellowstone Caldera. 

According to Forbes, the rock samples found in the Benham Rise ages more than 40 million years when the volcanic activity built the said large igneous massif. As per PHIVOLCS, Apo Laki, being the world’s largest caldera to date, poses no threat to the Philippines and its neighboring areas. When asked for possible future explosions, the team says not in the next million years. The government, though, after the study of Jenny Anne Barreto, Ray Wood, and John Milsom, consider deployment of researchers to determine the natural resources available in the area further.

What to Do During Earthquakes

The Philippines is now faced with such catastrophe posing a threat to human lives and properties. There are earthquakes triggered by selfish social activities like the impoundment of reservoirs, underground mining, and the injection of some fluids to underground formations, among many others, as stressed by the U.S.U.S. Geological Survey (USGS). This is one of the reasons why our Philippine government has had tight policies in allowing these activities. 

Natural earthquakes, however, like what happened in Mindanao cannot be prevented. BUT, mitigating the effects of such a catastrophe may be done significantly. How?

1. Be vigilant to earthquake hazards. Ground shaking, landslides, liquefaction, and possible tsunami are among these hazards. Residents and business owners alike must be aware and prepared of all these for safety purposes.

2. Build SAFE structures. The government, particularly the Engineering department of every city or municipality imposes safety requirements for building constructions. This needs to be strictly followed for each of our safety.

3. Be earthquake smart. Earthquake education is a must to each, and everyone may be a student or not, a resident of Mindanao or not. There is no excuse. Catastrophes cause panic, especially to those who refused proper education. You should know better as it’s you and your family’s safety you’re putting at stake.

Will Philippine Earthquakes Cause Volcanic Eruptions?

Well, perhaps.

Some strong quakes greater than magnitude 6, according to USGS, may be related to some volcanic eruptions. However, it also adds that it has to have enough eruptive magma and significant pressure within its storage region.

Circulating around social media are warnings of the Mount Apo’s possible explosion after the successive earthquakes. However, according to Phivolcs, from the epicenter of Tulunan, the nearest active volcanoes are Matutum Volcano and Parker Volcano that showed no significant signs of future volcanic eruptions.

The recent quakes are described as “tectonic in origin,” which means that it relates to the earth’s crust structure. Again, it’s not in any way connected to these active volcanoes. So the best thing to do is BE VIGILANT and rather STOP SPREADING FAKE NEWS.

With the damages that the recent quakes have caused in several areas in South Cotabato, Davao del Sur, and nearby provinces, the resilience and generosity had been once again evident in every single willing individual who reached out to help.

We can only hope that even though we cannot escape being in the typhoon belt and the ring of fire, we will be responsible enough and be ready for possible threats.

It pays to be vigilant, but it takes a courageous Filipino to survive significant calamities.