La Palma’s volcanic headache: what to do with all the lava and ash | volcanoes

For three months they have been subjected to the vagaries of a roaring volcano. Today, residents of the small Spanish island of La Palma are grappling with another dilemma: what to do with the millions of cubic meters of lava and ash it left behind.

The volcano rumbled for 85 days, ejecting ash and rivers of lava that engulfed more than 1,000 homes, cut off highways and choked out the lush banana plantations that drive the island’s economy.

The eruption was declared over on Christmas Day, leaving residents struggling with the daunting task of rebuilding. “It’s brutal,” said Javier Moreno, one of La Palma’s 80,000 residents. “The affected area looks like they erected the Berlin Wall, but made of black lava.”

A car covered in ashes in the Las Manchas neighborhood. Photography: Desiree Martin/AFP/Getty Images

In recent days, around 2,000 of the 7,000 evacuated residents have been allowed to return home. Many have arrived to find layers of powdery ash covering their homes, patios and plants – remnants of the more than 200 cubic meters of lava and ash expelled by the volcano.

“It’s an ongoing battle,” Moreno said. “You clean it today, tomorrow the wind still blows a few centimeters.”

In parts of the island, ash buried houses, engulfed verdant plantations and accumulated on embankments several meters high. Lava and ash reached beyond the island; Lava cascading into the ocean during the eruptions created two new peninsulas, measuring 44 and 5 hectares, while underwater footage revealed marine life covered in ash.

While round-the-clock efforts to clear the ash succeeded in storing some of it in specific areas such as an old quarry on the island, clearing incandescent lava flows that spread through neighborhoods and farmland proved trickier.

“They continue to store heat, with temperatures over 100 degrees [Celsius] in some areas,” said Inés Galindo, a geologist who heads the Canary Islands unit of the Spanish Geological and Mining Institute.

Once the lava has cooled – a process that could take months – it might in some cases be easier to build on it than to break it up and remove it, she added.

Gladys Jeronimo, 65, cleans sand and ashes from her home in the Las Manchas neighborhood.
Gladys Jeronimo, 65, cleans sand and ashes from her home in the Las Manchas neighborhood. Photography: Desiree Martin/AFP/Getty Images

As researchers and officials scramble to figure out what could be done with the materials spewed out by the volcano, they turned to history. In the neighboring island of Lanzarote, a six-year eruption in 1730 left parts of the island covered in volcanic material. “The particles were porous and able to retain water in the soil…they took advantage of this to plant vines,” Galindo said.

She and her team are currently studying the properties of the ash tree in La Palma to see if it could be used in the same way, while another team of researchers is investigating whether the mineral-rich soil could be used as fertilizer.

Regional officials, meanwhile, are exploring the possibility of using the ashes to build homes, roads and bridges across the island. “It is not an original idea, we are using the techniques used by the Romans,” said Javier Juvera, an engineer with the Canary Islands public works department. “The Romans worked with the ashes that came out of [Mount] Vesuvius, using them to build their basilicas and buildings.

A crack is seen next to an ash-covered house in La Palma, December 2021.
A crack is seen next to an ash-covered house in La Palma, December 2021. Photograph: Emilio Morenatti/AP

His team is now working to determine if the ash scattered on the island is similar to volcanic ash used by the Romans to bind rock fragments. If so, it could result in a sustainable building material and play a role in rebuilding the island, where regional officials have estimated the loss of buildings and infrastructure at more than 900 million euros. (£750 million).

Juvera described the ideas as a seemingly natural fit for an archipelago carved out of volcanic activity spanning millions of years. “In the Canary Islands we are used to working with volcanic materials,” he said, citing the long-standing practice of mixing cement and materials extracted from volcanic cones to build houses.

Juvera and Galindo said it would be months before they had definitive answers on what could be done with the black ash blizzard ejected from the volcano. “The amount of material is so huge – there are images of houses that have been practically buried under ash,” Juvera said. “But if we don’t find value in it, it becomes waste.”

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