Mount Cumbre Vieja is set in a national park of the same name in the south of the island, which lies 133 miles west of Tenerife.
Shortly before the eruption at 3.15pm local time, the island authorities started evacuating elderly locals and farm animals in the vicinity; two hours later, five rivers of lava were trickling down the hillside, while after dark local photographers captured dramatic pictures of lava shooting up towards the night sky.
But how destructive is the eruption, and will it disrupt travel to the Canary Islands?
Here’s everything we know so far.
How serious is the eruption?
This is the first time Cumbe Vieja, a mountain range and active volcano, has erupted this century – it previously erupted twice in the 20th century, in 1949 and 1971.
A 4.2 magnitude earthquake occurred before the eruption, on the western slopes of the range.
So far there have been no casualties, though the local authorities say eight homes have been destroyed by the lava flow. The eruption has also caused some forest fires around the hillside.
Experts believe the lava flow could continue for up to six or eight weeks.
“The lava flows, that have been descending the slopes of the municipality of El Paso in the Cabeza de Vaca area, are advancing at approximately 700 metres per hour, and thermal images have determined that they have a temperature of 1,075 degrees Celsius,” reported Canarian Weekly this morning.
The main areas being evacuated are Cabeza de Vaca and El Paraiso in the El Paso area, with around 5,000 locals moved away from the scene.
However, authorities have said they may need to evacuate as many as 10,000 people in the wake of the incident.
Local emergency services were well prepared for the blast, which has been expected and monitored since the peak first showed signs of activity on 11 September.
The chief concern among local authorities at this stage is the damage the lava flow will cause to local properties and farms.
Parts of the island’s southwest coast may also be affected by landslides and rock falls, with tourists understandably being urged to stay away from the wider national park.
Are flights or holidays to the Canary Islands being cancelled?
So far, no flights or holidays from the UK to the Canary Islands, or vice versa, have been cancelled.
Local Canarian airline Binter today said it cancelled four flights to and from the neighbouring island of La Gomera, due to the eruption.
La Palma’s airport, in Santa Cruz in the north of the island, did close for around an hour on Sunday in the immediate aftermath of the eruption.
Two aircraft were diverted to Tenerife North airport, while a Tui plane was held on the ground during that time before being cleared for take off to Amsterdam.
Air traffic has now resumed as normal in La Palma, with no reports of volcanic smoke disrupting international flights, though the airspace immediately above the volcanic site is currently a no-fly zone.
Tui, which operates direct flights from the UK to La Palma, said: “Currently we don’t have any affected flights, however we will continue to monitor the situation closely and will contact customers should their holiday be impacted.”
The Foreign Office has updated its travel advice for Spain with an alert about the eruption, saying: “If you are in an affected area you should follow the advice of local authorities, including social media updates from Cabildo de La Palma. If you are planning to travel to the island imminently you are encouraged to contact your tour operators / airlines.”
What are the authorities saying?
Spanish prime minister Pedro Sanchez is on the island at the moment, and told press: “The citizens of La Palma have to remain calm. Their security is guaranteed.
“We have all the resources and all the troops, citizens can rest easy,” he added.
Canarian prime minister Sergio Rodriguez has said: “The lava is moving towards the coast and the damage will be material. According to experts there are about 17-20 million cubic meters of lava.”