Volcanic mountains

Tonga depends on rainfall to harness dangerous volcanic ash, which could be used to rejuvenate the Pacific nation

The volcanic ash that blankets much of Tonga poses serious health risks if inhaled, but once enough rain hits the Pacific nation, the ash could help rejuvenate the country’s soil and is already being collected for building materials.

Efforts to clear a thick layer of ash continue two weeks after the eruption of the Hunga Tonga-Hunga Ha’apai volcano triggered a tsunami and caused widespread destruction across the archipelago.

Tevita H Hafoka lives in Tonga’s capital, Nuku’alofa, and said it felt like the city was in grayscale before the first decent rain finally arrived on Friday.

“Everything was covered in ash: it was like a sepia image,” Hafoka said.

“We’ve had a lot of rain since [Friday] morning… and the rain helped tremendously to remove the dust and ash from the roofs. »

He said trees covered in ash were losing their leaves and new shoots were appearing.

The volcanic eruption leaves islands across Tonga covered in ash.(Reuters: Malau Media)

Ash is used to slow traffic, fertilize the soil

Mr Hafoka said the Tongans were a resilient and resourceful people and were already working to find uses for the ash, including slowing down cars.

“There was a lot of ash and vehicles, especially heavy vehicles, were driving around and kicking all the dust into the air… so people even resorted to piling [the dust] and use it as a speed bump to slow down cars,” he said.

“People package it to use in cement for construction work.

“And I heard on the radio the other day, some people try to sell [the ash].

Tonga’s Department of Lands and Natural Resources Deputy Geologist Pupunu Tukuafu said locals also plan to use the ash to add nutrients to the soil.

“A lot of people collected the ashes from their roofs and roads as fertilizer for gardening,” Mr Tukuafu said.

Professor Scott Bryan from the School of Earth and Atmospheric Sciences at the Queensland University of Technology said the ash would help bring nutrients to the main islands of Tonga, which were essentially raised coral reefs.

“The islands themselves are made up of very carbonate-rich rocks,” Professor Bryan said.

“As for soils that are made up of limestone or carbonate, they are quite poor in nutrients.

“So really, the ash being glassy, ​​is going to break down relatively quickly and provide a lot of nutrients to their soils.

Satellite images of houses in Tonga before the volcano.  One is clear and the other is blackened with volcanic ash.
Houses and buildings in Tonga before and after the eruption of the Hunga Tonga-Hunga Ha’apai volcano.(Provided: Satellite image/©2022 Maxar Technologies)

While Friday’s rainfall was welcomed by locals, more is needed to eliminate the immediate threat the ash poses to people and natural resources.

The New Zealand Meteorological Service said that although it has been mostly dry in Tonga since the eruption, rainfall is expected to increase.

“A few showers are expected over the next few days, but shower activity is expected to increase next week with a strange thunderstorm also a possibility,” said Met Service chief meteorologist Stephen Glassey.

“Precipitation amounts in the tropics are difficult to predict because it depends on whether a thunderstorm occurs over land or over the ocean.”

In the meantime, the ashes pose a risk to people, water and food sources and residents have been advised to wear masks to avoid inhaling the ashes.

Ash samples have been sent to New Zealand and are being tested at the University of Auckland, Mr Tukuafu said.

Professor Bryan said that once more was known about the specific compounds in the ash, authorities would be able to assess the risk of diseases such as silicosis, which is caused by breathing in tiny particles of silica, a common mineral found in sand, quartz and other rocks.

Water, land and livestock at risk

Mr Tukuafu said the ministry was still surveying the damage on the outer islands and testing household water tanks to see if they were safe to use.

While rain could help clear trees and roofs of ash to restore local rainwater supplies, recovering crops and livestock could take longer, Tukuafu said.

Markets in Tonga shortly after the volcanic eruption show buildings and boats covered in ash.
This is Tongatapu the day after the eruption and tsunami. Two weeks later, residents are still removing the ashes. (Reuters: Malau Media)

“Most root crops… [they’ve] already dried up and that could be a big problem for us in the months to come and maybe years to come,” he said.

“Root crops, especially yams, kumara…bananas, etc.

“Most food sources are still covered in ash and some cattle are struggling to find food sources and with limited water sources at the moment it could be difficult to find water for the cattle” .

He said Tonga’s Department of Fisheries was encouraging people to fish in deep water to avoid ash contamination.

Mr Tukuafu said Tonga may be forced to rely on imported sources of food and water until local sources are deemed safe.