Ford Cochran says that hundreds of metres beneath one of Iceland’s largest glaciers, there are signs of an imminent volcanic eruption.

Cochran said that it could be one of the most powerful the country has seen in almost a century.

If it were to erupt, Katla, with its 10km (6.2 mile) crater, could cause catastrophic flooding as it melts the frozen surface of its caldera and sends billions of gallons of water hrough Iceland’s east coast and into the Atlantic Ocean.

“There have been more than 500 tremors in and around the caldera of Katla just in the last month, which suggests the motion of magma. And that certainly suggests an eruption may be imminent, Cochran told the BBC.

Scientists have been monitoring the area since July 9, when there appears to have been a small eruption – one large enough, however, to cause flooding and wash away bridges.

According to historical records kept in Iceland, Katla erupts every 40 to 80 years. The last major eruption happened in 1918 and produced such a large glacier meltdown that icebergs were swept by the resulting floods into the ocean.

The volume of water produced in a 1755 eruption equalled that of the world’s largest rivers combined.

And in 1783, an Icelandic system of volcanoes, including Katla, erupted non-stop for eight months. It generated so much ash, hydrogen fluoride and sulphur dioxide that it killed one in five Icelanders and half of the country’s livestock.