Juan Medina and Silvio Castellanos

LA PALMA (Spain) – Three weeks after the eruption, blocks of molten lava rolled down a slope on La Palma’s Spanish island. A series of tremors shook ground and a number of quakes erupted on Sunday.

On Sunday there were 21 seismic events, the Spanish National Geological Institute said. These movements shaken the ground at El Paso’s villages of Fuencaliente, Mazo and Fuencaliente.

According to the Spanish Institute of Geology and Mining, three-storey buildings were able to accommodate the blocks of magma that flowed down from the Cumbre Vieja volcano’s side.

Stavros Meselidis, a spokesperson at ING told Reuters that Saturday’s partial cone collapse was near the volcano’s emission vent.

Spain’s National Security Department tweeted that “The northern flank of Cumbre Vieja volcano collapsed has led to the release of large chunks of material and new flows that run through already evacuated areas.”

“The Camino de La Gata industrial estate has been affected by the lava and it is now possible to build new structures.”

According to the Canary Islands Volcanic Institute, 1,186 buildings have been destroyed by rivers of lava since Sept. 19’s eruption.

Lava has engulfed 493 hectares (1,218 acres) of land, said Miguel Ángel Morcuende, technical director of the Canary Islands Volcanic Emergency Plan (Pevolca) organisation.

Around 6,000 people were evacuated from La Palma’s homes by the authorities. The island has approximately 83,000 residents.

On Saturday, lightning was visible near an eruption. Geophysical research Letters published an article in 2016 showing that lightning can be generated by volcanic eruptions. This is because of the interaction between the ash particles and creates an electricity charge.