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Friday, March 29, 2024

Why is there a Pacific Ring of Fire?

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THE past few weeks have been eventful in the Pacific ‘Ring of Fire.’

Last Tuesday, a volcanic eruption in Japan caused an avalanche that killed one and injured several others. On the same day, a magnitude 6.0 earthquake shook parts of Indonesia, causing buildings to sway in the capital Jakarta. Not long after that, a stronger magnitude 7.9 earthquake struck Alaska, which prompted tsunami warnings for nearby areas.

Here in the Philippines, the Mayon Volcano has been actively spewing lava and ash for several days this week, with the Philippine Institute of Volcanology and Seismology (Phivolcs) recording 15 volcanic earthquakes.

This is all normal, according to earth scientists. After all, the Ring of Fire is a place where volcanic activity and earthquakes are to be expected. Given the likelihood that these events will happen in the region, it should not be surprising that they sometimes happen one after the other.

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What is the Pacific Ring of Fire, anyway? And why does it exist? Let us take a close look at the science.

The Pacific Ring of Fire is an arc around the Pacific Ocean where there are many active volcanoes and where earthquakes frequently happen. It also hosts many dormant volcanoes that were very active in the past. The Ring of Fire includes New Zealand, Papua New Guinea, Indonesia, Malaysia, the Philippines, Japan, Alaska, and nearly the entire west coast of North and South America. It is the site of around 90 percent of the world’s earthquakes and is home to 75 percent of the world’s active and dormant volcanoes.

The Philippines is well within the Ring of Fire. This is can be seen in the number of volcanoes in the region as well as the frequency of earthquakes in the country.

Why is there a Ring of Fire? Two words: plate tectonics. It is the unifying theory of the earth sciences. It helps explain nearly everything in the earth sciences, from why there are continents and oceans to why different kinds of rocks and minerals exist in different parts of the world.

According to plate tectonics, the Earth’s outermost layer is relatively thin and made of several rigid blocks or chunks called tectonic plates.

According to the theory, the tectonic plates rest on a layer of rock that constantly deforms or “flows” due to the heat coming from underneath the Earth. As a result, the tectonic plates are constantly shifting about instead of staying in place. As they shift, the tectonic plates often push against each other, causing the formation of mountains, trenches, and valleys. Their constant jostling also results in earthquakes. This is why most of the world’s earthquakes happen near the boundary between two or more tectonic plates.

Plates can have three kinds of boundaries: ones where they move away from each other, ones where they slide past each other, and ones where they move toward each other.

The third kind results in a collision between plates.

Not all tectonic plates are made equal. Some plates, like the ones making up continents, are thicker and lighter, making them “float” above the oceans. Other plates, like the ones forming the ocean basins, are thinner and heavier.

When two continental plates collide, they push each other up, forming a mountain range, such as the Himalayas.

On the other hand, when a heavier oceanic plate collides with a lighter continental plate, the oceanic plate sinks underneath the continental plate.

Most of the Pacific Ocean rests on top of an oceanic plate called the Pacific Plate. As the Pacific Plate collides with its neighbors, it generally sinks underneath them. The part that sinks gets molten by the heat from inside the Earth. This results in the production of magma, which then rises to the surface to produce volcanoes. This is why many volcanoes ring the Pacific Ocean.

The “sinking” of the Pacific Plate underneath neighboring plates is also the reason why many earthquakes occur around it. Of three kinds of plate boundaries, the third kind where plates collide usually result in the strongest earthquakes.

The Earth is the only major body in the Solar System with active plate tectonics. Other bodies such as Mercury, Venus, Mars, and the Moon, do not have enough remaining heat from their interior to have plate tectonics.

Many scientists think the existence of life on Earth owes a great deal to plate tectonics. Perhaps life, or at least life as we know and live it, might not even exist without it. Hence, as destructive earthquakes and volcanoes are, they can be thought of as a byproduct of a process that made life possible in the first place.

Pecier Decierdo is the resident physicist and astronomer of The Mind Museum.

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