LA PALMA, Spain—Buildings near the volcano on the Spanish island of La Palma were engulfed by rivers of lava early on Saturday, with the drama of the red-hot eruption intensified by the spectacle of flashes of lightning. The magma destroyed at least four buildings in the village of Callejon de la Gata, Reuters witnesses said. There were a series of 37 seismic movements on Saturday, with the largest measuring 4.1, the Spanish National Geological Institute said. The Cumbre Vieja volcano began erupting on Sept. 19 and has destroyed more than 800 buildings and forced the evacuation of about 6,000 people from their homes on the island. La Palma, with a population of about 83,000, is one of the Canary Islands in the Atlantic. 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 …