What you are seeing in these images and the video that comes is a different eruption than the others. The blue tint that surrounds the lava comes from the flames produced by the sulfuric gases.
The volcano contains large amounts of pure sulfur, which emits a violet color when it burns, filling the air with toxic fumes. The image above was taken on an erupting volcano in Ethiopia.
Blue volcano
The French photographer Olivier Grunewald has specialized in this kind of images, which he uses without filters or image modifications. To achieve this, I have to wait until nightfall, when the blue flames are visible. Work with a gas mask to avoid breathing toxic fumes.
It is not the first time that Grunewald travels around the world to take pictures of blue lava. In January, I traveled to Indonesia to photograph the Kawah Ijen volcano. The volcano is the subject of a new documentary produced by Grunewald and Régis Etienne, the president of the Geneva Volcanology Society, which was launched earlier this year.