Natural Disasters

What happened after the volcano at Tonga

Here is a primer on what changed after the volcano in Tonga erupted recently

By DTE Staff
Published: Monday 24 January 2022

The massive volcanic eruption and tsunami in Tonga has caused catastrophic damage, with homes destroyed and many communities covered in a thick layer of ash.

The port in the capital, Nuku'alofa on the main island of Tongatapu, has been severely damaged, with many buildings near the waterfront completely flattened.

Extensive damage to property, especially on the western beaches of Tongatapu. The residents have been moved to evacuation centres. There is also growing concern for residents of smaller, low-lying islands to the north of Tongatapu.

At the main airport for the islands, Fua'amotu International Airport, piles of ash are hindering operations and international aid efforts. Volunteers have been sweeping the runway of the main airport to allow planes to land.

And, little appears to be left of Hunga-Tonga-Hunga-Ha’apai, where the volcanic eruption happened on Saturday. Satellite images show only a small amount of land remains above water.

The plumes of gas, smoke and debris from the volcano reached 30 kilometres into the sky. But the main health concerns are from ash in the air which people are breathing.

At the moment, there would be high levels of sulphur in the air and water. This is a risk to drinking water and fishing, which is vital to the Tongan people and could lead to a rise in water temperatures. So, the priority is to find safe shelter and clean water and to escape the volcanic smog.

But will this underwater volcanic eruption affect the global climate?

The gases spewing out of the volcano include sulphur dioxide (SO2), which is of particular interest because of its global cooling effect.

On June 12, 1991, Pinatubo spewed about 15 million tonnes of sulphur dioxide into the stratosphere. SO2 reacts with water to form sulphuric acid droplets, which become a part of aerosol particles.

Aerosols are tiny liquid droplets suspended in the air. The sulphuric acid-rich aerosol particles induce cooling by reflecting the incoming sunlight into space.

The total mass of SO2 in the volcanic cloud was 20 teragram (Tg). The particles remained in the stratosphere for three-four years after the explosion. Researchers recorded a 0.5 degrees Celsius (°C) drop in the average global temperature over large parts of the earth between 1992 and 1993.

The Tonga volcanic cloud contains roughly 0.4 Tg of SO2. This means it is unlikely to have a significant cooling effect on temperatures globally.

Along with SO2, the eruption also released nitrogen oxide — two gases that create acid rain when they interact with water and oxygen in the atmosphere. Acid rain causes widespread crop damage and could affect Tongan staples such as taro, corn, bananas and garden vegetables.

Long-lasting effects include damage to coral reefs, eroding coastlines and disrupting fisheries.

Marine life 

Falling ash could also damage coral reefs. Vast areas of the reefs in the immediate impact area at Hunga Tonga are probably buried and smothered by large deposits of volcanic ash. Eruptions such as these also release more iron into the water, which can boost the growth of blue-green algae and sponges that further degrade reefs.

Freak waves

In the aftermath of the eruption, a tsunami wave of 1.19 metres was recorded. Tsunamis are known to cause rapid coastal erosion, which in turn causes a loss of coral reefs and affect the ability to cope with rising waters and storm surges.

Peru oil spill 

The freak waves produced by the eruption have also been blamed for causing an oil spill at the Pampilla Refinery in Peru, belonging to the Spanish company Repsol. Peruvian authorities sealed off three beaches on Monday after a “limited spill” of oil off the coast of Callao and Ventanilla districts near the capital, Lima. This affects the fishermen, the population that they feed with the fish and marine animals.

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