Fears of an eruption have been going since the end of July, when El Hierro experienced the first of what has become more than 10,000 tremors - collectively known as an earthquake 'swarm'.
ISLANDS PERCHED ON THE SHIFTING AFRICAN PLATE
Under the Canary Islands lies an area of magma which is able to break through to the surface when the African Plate - on which the islands sit - shifts. It is to this that the islands owe their very existence.
Most of the islands are still volcanically active and there has been speculation that a smaller, previously undetected fault line also runs through the chain.
El Hierro - which means 'iron' in Spanish - was formed after three volcanic eruptions 100 million years ago and is topped by a volcano more than 6,000ft high.
Volcanic activity - mainly where three ridge lines converge - has caused El Hierro to expand continually. The last time it erupted was in 1793.
Some 50,000 years ago, massive landslides triggered by earthquakes caused a large part of the island to crack off and fall into the Atlantic Ocean, according to Irish Weather Online.
That created the El Golfo valley on the island and caused an 300ft-high tsunami that probably reached the American coast.
This feeds into the belief that volcanic activity on La Palma - the most tectonically active of the Canary Islands - could trigger a mega-tsunami.
The theory - which has never been confirmed - claims that a possible fault line through the island would cause a major landslide under certain circumstances.
That landslide would then spark a tsunami that would cause extensive damage all down the Atlantic Coast of the U.S., the Caribbean, Western Europe, West Africa and the east coast of South America.
Eruption: A diagram showing where the epicentres of tremors have been. El Hierro was formed when three volcanoes erupted 100 million years ago
Read more: http://www.dailymail.co.uk/sciencetech/article-2058436/El-Hierro-volcano-ready-eruption-Homes-evacuated-Spains-southern-Canary-Islands.html#ixzz1d4nTFEjW
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