LA PALMA, SPAIN (REUTERS) - Red-hot lava engulfed the land Jose Roberto Sanchez inherited from his parents on Saturday (Oct 9) and lightning flashed around the rim of the volcano that has been erupting on the Spanish island of La Palma for almost three weeks.

There were 37 seismic movements on Saturday, with the largest measuring 4.1, the Spanish National Geological Institute said, but La Palma's airport reopened after being closed since Thursday because of ash, Spanish air traffic operator Aena said.

All other Canary Islands airports are open.

The magma streaming down the hillside from the Cumbre Vieja volcano destroyed at least four village buildings, some of nearly 1,150 buildings and surrounding land destroyed since the volcano began erupting on Sept 19.

"The memories of my parents, the inheritance I had there, it's all gone," Sanchez told Reuters of the land his parents owned in Todoque in the west of the island.

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

Some people, like Clara Maria, 70, who also lives in Todoque, have so far escaped the impact.

"The lava has not yet reached my house. (It) was 50 years of sacrifice, stone by stone we built it. I have hope and faith that it will be saved," she said.

About 6,000 people have been evacuated from their homes on La Palma, which has about 83,000 inhabitants.

Lightning flashes were seen near the eruption early on Saturday. A study published in 2016 by the journal Geophysical Research Letters found lightning can be produced during volcanic eruptions because the collision of ash particles creates an electrical charge.

Airlines flying to the Canary Islands were advised to load extra fuel in case planes had to change course or delay landing because of ash, said a spokesman for Enaire, which controls navigation in Spanish airspace.