The Cumbre Vieja volcano roared to life on September 19, 2021, sending fountains of lava into the air and large rivers of lava streaming towards villages towards the south of La Palma. The eruption has been persistent and at times explosive. Tremors and small earthquakes frequently shake the ground, while dark plumes of volcanic ash and light clouds of steam and gas rise from the summit daily. Lava has reached the southwestern coast, forming a broad delta that stretches into the North Atlantic Ocean. More than a thousand homes and buildings have been destroyed as of October 9 and more than 6,000 people have been forced to flee their homes and farms.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of the eruption on October 7. A plume of brown ash blows more than 100 miles (160 km) to the northeast over the Atlantic Ocean. This image also captures a blue swirl southwest of La Palma Island. The origin of this appears to be from the summit of Cumbre Vieja, which makes it likely that it is a cloud of gas, steam, or haze. It would be unusual, but not impossible, for forcefully ejected ash to rise high in the atmosphere and be carried by strong upper-level winds in one direction while steam and gas flowing less forcefully out of the volcano to remain low and be carried in a different direction by winds closer to ground level. Steam is typically white in true-color images, but a type of volcanic smog known as “vog” may appear as a blue-gray haze. Vog is created when sulfur dioxide and other volcanic pollutants mix with oxygen and water vapor in the presence of sunlight.
As of the morning of October 9, the Toulouse Volcanic Ash Advisory Center declared a code red for aircraft passing through the region. Ash plumes were reaching 2 to 3 kilometers (1-2 miles) in altitude. The eruption has not been energetic enough to inject large amounts of ash and gases into the stratosphere, where they can have strong and lasting effects on weather and climate.
According to news reports, airborne ash has led to intermittent closures of the airports on La Palma and other Canary Islands. Air quality at ground level is episodically poor depending on the wind direction and intensity. And ash falling from the sky has coated some of La Palma’s salt flats, disrupting efforts at salt production.
In late September, scientists from the Instituto Volcanológico de Canarias (INVOLCAN) suggested that the current eruption could persist for weeks to months. Cumbre Vieja last erupted about 50 years ago.