A picture taken by Francisco Rodriguez of erupting Calbuco volcano, near the city of Puerto Montt, in southern Chile. Calbuco erupted explosively April 22, 2015, sending an ash plume to more than 15 km above the crater. This photo won the first prize (general category) in the Hamdan Bin Mohammed Bin Rashid Al Maktoum International Photography Awards (HIPA). Image Credit: HIPA


  • The earth’s tectonic plates move constantly.
  • This constancy of movement is the trigger behind earthquakes and volcanic eruptions.
  • It’s the same reason why Mt Everest is still growing 10 mm per year.

People everywhere are spellbound by the shaking of the ground. What’s even more fascinating is that earthquakes are a common occurrence.

Here’s one interesting fact: about 20,000 earthquakes are located around the globe each year — or approximately 55 per day — according to the National Earthquake Information Centre, under the US Geological Service (USGS).

A higher estimate, however, states that about 500,000 detectable earthquakes happen each year — 100,000 of those can be felt — and about 100 of them cause damage.

What causes earthquakes?

It goes back to tectonic plates: they are always moving, albeit only slowly, but do get stuck at their edges due to friction. Earthquakes occur due to a sudden slip on a fault — or a sudden release of stress along faults — in the earth's crust.

As these plates continue to move, it leads to a steady build-up of pressure in the rock strata on both sides of a fault — until the stress becomes so great that it is released in a sudden, jerky movement.

An earthquake releases energy in “waves”, measured using the Richter scale. These waves travel through the earth's crust and cause the shaking that we feel.

Biggest earthquakes
Image Credit: Gulf News | USGS

Why is the Pacific Rim called the ‘Ring of Fire’?

The “Pacific Ring of Fire” is near the “earthquake belt” — so called because more than 80 per cent of the total of about 1,450 active volcanoes are concentrated in this region.

It’s also known as the “Rim of Fire”, where volcanic eruptions and earthquakes occur regularly.

Among these are 40 active volcanoes in the Andes (South America), nearly 300 in the Philippines (most of them dormant or extinct), 70 in Indonesia and 40 in Japan.

Pacific Ring of Fire
Image Credit: AFP

The Pacific Ocean floor forms a massive plate, which also includes the western side of the Americas. 
The Pacific Plate “grinds” northwestward past the North American Plate at a rate of about two inches per year.

Parts of the San Andreas Fault system adapt to this movement by constant "creep" resulting in many tiny shocks and a few moderate earth tremors.

What are the countries within this ‘ring’?
This Pacific Ring of Fire covers the continents ot Antarctica, South America, North America, Asia and the islands on the southwest Pacific Ocean. The countries | territories include:

Costa Rica
El Salvador
United States
Papua New Guinea
Solomon Islands
New Zealand

Why isn’t there an “Atlantic Ring of Fire”, or around other oceans?

The "Pacific Ring of Fire” is a vast area, the largest ocean in the world. This rim sees active plate tectonic movements and collisions of “lithospheric” — oceanic crust with part of the upper mantle — plates.

It is through this constant movement of tectonic plates, that oceanic trenches, earthquakes, mountains and volcanoes arise.

Compared to the Pacific, however, things are much quieter in the Atlantic. While the Mid-Atlantic Ridge (which has formed Iceland) is the third most prominent earthquake belt, the Atlantic’s oceanic lithospheric plate has not begun to sink along the margins — yet, according to science site phys.org.


number of known active or potentially active volcanoes around the world (excluding volcanoes on the sea floor).

One estimate states that it would take another 20 million years before the continents around the Atlantic would develop active continental margins — enough to produce more earthquakes and kick up volcanic eruptions.

Mount everest
HOW COME MT EVEREST IS STILL GROWING? As you read this, the collision between the continental plates is happening. For example, the Indian subcontinent continues to move north by 5 cm (2 inches) a year, causing Mt Everest to grow by about 4mm per year. Other parts of the Himalayas are rising at around 10mm (1/4 of an inch) per year. This pattern of movement goes back 50 million years. That’s how the Himalayan mountain range and the Tibetan plateau were formed — with the Indian tectonic plate colliding into the “Eurasian” plate. It continues till today. It’s the reason why the world’s tallest peak continues to grow.

How do tectonic plate collisions creates volcanoes and quakes?

As tectonic plates collide, the impact can be either of the two scenarios:

[1] The edges of one or both plates can buckle up into a mountain range;

[2] One of the plates may bend down into a deep seafloor trench.

A "chain" of volcanoes often forms parallel to convergent plate boundaries, and powerful earthquakes are common along these boundaries.

About 80 per cent of volcanoes occur along subduction zones, and 15 percent occur along rift zones. That’s when the “real” fully-active subduction zones will be formed.

How many volcanoes are there in the world?

Currently, there are about 1,450 known active or potentially active volcanoes around the world. This does not include the continuous belts of volcanoes on the ocean floor at places like the Mid-Atlantic Ridge. More than 3 out of 10 volcanoes — about 500 of 1,450 — have erupted in historical time.

What do volcanoes have to do with earthquakes?

They are both caused by the earth's tectonic plate movements, which results in heat and energy releasing from the Earth's core. Earthquakes can trigger volcanic eruptions through tectonic plate movements. Similarly, volcanoes can trigger earthquakes through the movement of magma within a volcano.

Mt Pinatubo, the second-largest volcanic eruption of the 20th century, is on the island of Luzon in the Philippines, an hour by car from Manila. About 800 people were killed and 100,000 became homeless when it erupted in 1991.

The events of the 1991 Mount Pinatubo eruption began in July 1990, when a magnitude 7.8 earthquake occurred 100 kilometers (62 miles) northeast of the volcano’s region, and was determined to result in its “reawakening”.

When the Mount Pinatubo erupted in the Philippines in 1991, the cloud of ash and sulphate particles deflected enough sunlight to cool the planet
Mt Pinatubo’s eruption climaxed on June 15, 1991, when millions of tons of sulfur dioxide were discharged into the atmosphere, resulting in a decrease in the temperature worldwide over the next few years.
Image Credit: Vijith Pulikkal | Gulf News