MADRID – The airport on the Spanish island of La Palma closed again on Thursday due to ash fall from a volcano that has erupted for nearly three weeks.

Scientists said the course of the eruption was unpredictable. It has calmed down in recent days, but the Canary Islands volcano continues to spew lava, and 16 earthquakes up to magnitude 3.5 have rocked the area in the past 24 hours, a declared the National Geographic Institute.

The lava forced the evacuation of more than 6,000 people and destroyed more than 600 homes. The ash cloud temporarily closed La Palma airport last month.

Officials said the molten rock from the crater is now flowing into a so-called lava tube under the earlier hardened lava, directly into the sea. This has allayed fears that it will spread more widely and cause more destruction. .

The German Geoscience Research Center, which sent a team to La Palma, said the lava flow is 6,300 meters (6,900 yards) long, more than 1,000 meters (1,100 yards) wide at its widest point, and up to 25 meters (82 feet)) thick.

The centre’s volcanology researcher Thomas Walter said the situation was still tense and unpredictable.

“It is still too early to say … how this rash will develop,” he said in a statement.

Rapid evacuations avoided the victims of the eruption, and most of the island of about 85,000 people remains untouched.

The volcanic Canary Islands lie off the northwest coast of Africa.