The Spanish government have issued a yellow alert following an increased level of persistent seismic activity, described as an "earthquake swarm". The epicentre is on the island of El Hierro - the smallest of the Canary Islands, to the west of Tenerife and Gran Canaria. The island, popular with tourists, has seen over 8,000 tremors in two months, 150 since yesterday and experts fear an eruption could happen imminently.

Around 10,000 people live on the 108-square mile island and 53 people have been evacuated from their homes so far following landslide fears. However, a mass emergency evacuation is now possible with the army on standby for helping out in such an event and residents preparing to flee.

The British Foreign Office advises: "The local government authorities have raised the risk level of a volcanic eruption from green to yellow and taken preventative measures in case of a volcanic disruption, deploying extra resources from the military and emergency services to the island. Local authorities are also on stand-by to effect an evacuation should this become necessary."

Fortunately, no cruise ships are due to call at El Hierro, but there are several scheduled to call at neighbouring islands over the next few weeks.

Ships visiting include Independence of the Seas, Adventure of the Seas and Mariner of the Seas, Silver Spirit, Ventura, Queen Mary 2, Costa Deliziosa, MSC Melody, HAL's Ryndam and Boudicca, Black Watch and Balmoral.

A volcanic eruption has not taken place on any of the Canary Islands since Las Palmas in 1971 but an expert has warned that an eruption on El Hierro could take place in, “days, weeks or months,” according to Tom Worden of the Mail Online. Juan Carlos Carrecedo said, “There is a ball of magma rising to the surface producing a series of ruptures which generate seismic activity. We don’t know if that ball of magma will break through the crust and cause an eruption.”

A spokeswoman for Royal Caribbean said: "We are currently monitoring the volcanic activity on El Hierro to ensure guests enjoy a safe and comfortable cruise. At this time, Independence of the Seas and Adventure of the Seas are still scheduled to make all of their ports of calls. The safety of our guests and crew is always our foremost concern."