Volcanic ash continues to fall, and warnings of more danger lie ahead.
Pyroclastic flows “contain a high-density mixture of hot lava blocks, pumice, ash and volcanic gas. They move at very high speed along volcanic slopes, usually along valleys,” the USGS said, “destroying almost everything in their path.”
“Based on visual observations and satellite images, the intervals are associated with periods of explosive activity or improved ventilation,” he said.
“Thunder and lightning were experienced during these periods.”
Ash had continued to fall on the island overnight, affecting neighboring islands, the Grenadines, Barbados and St. Lucia, too, he said. “Explosions and associated ash fall, of similar or greater magnitude, are likely to continue in the coming days.”
On Thursday, Prime Minister Ralph Gonsalves declared a disaster alert in response to a change in the volcano’s eruptive activity. He issued an evacuation order for all residents living in a “red zone”. Gonsalves has said it could take four months for life on the island to return to normal.
Authorities have said it is likely that explosive eruptions could continue “for days and possibly weeks” after the initial eruption on Friday released an ash plume reaching 20,000 feet (6,096 meters) into the air.
La Soufrière is located on the largest island of the St. Vincent and the Grenadines chain.
CNN’s Patrick Oppmann reported from Havana and Claudia Dominguez from Atlanta. CNN’s Susannah Cullinane, Theresa Waldrup and Radina Gigova also contributed to this report.