The northern slope of the crater collapsed at the Cumbre Vieja volcano.

Streams of molten lava the size of a three-story house flowed down a hillside on the Spanish island of Palma, where a series of tremors shook the earth three weeks after the eruption of the volcano.

On Sunday, the National Geological Institute of Spain reported 21 seismic tremors of magnitude up to 3.8. The earthquake was felt in the villages of Maso, Fuencalente, and El Paso.

Streams of incandescent lava flowed down the slope of the Cumbre Vieja volcano, the Spanish Institute of Geology and Mining reported.

From Monday, the Spanish Navy will be involved in cleaning up the territory from volcanic ash, Defense Minister Margarita Robles said on Sunday.

Lava flows, whose temperature reached 1240 degrees Celsius, destroyed the last few buildings in the village of Todoke, the Institute of Volcanology of the Canary Islands reported.

On Saturday, the volcano’s cone at its mouth partially collapsed, Stavros Meletlidis, a representative of the National Geological Institute, told Reuters.

“The collapse of the northern slope of the Cumbre Vieja volcano led to the release of large blocks of material and the emergence of new flows that went through already evacuated areas,” the Spanish Department of National Security said on Twitter.

Since the eruption began on September 19, lava flows have destroyed 1,186 buildings, the Institute of Volcanology of the Canary Islands reported.

About 6 thousand people from the 83 thousand population of the island of Palma were evacuated from their homes.

On Saturday night, lightning was visible in the area of the eruption. A study published in 2016 in the journal Geophysical Research Letters states that volcanic eruptions can be accompanied by lightning, as the collision of ash particles creates an electric charge.