The histories, written by Irish monks, over 1,200 years, have proved to be a useful resource to researchers who were examining climate change in relation to volcanic explosions.

The ash cloud from the Icelandic volcano has begun moving back into Irish airspace, bringing with it fears of a health crisis.

The government task force has warned that the ash may fall on Ireland on Monday or Tuesday because of rainfall and will leave a dust-like coating on the ground.

There were widespread fears of health problems, especially for those with respiratory illnesses, but Minister for Transport Noel Dempsey stated officials were not worried.

“It’s not going to be covered in this stuff,” Mr. Dempsey said.

“There is no indication at the moment. If the wind changes, if the weather conditions change, then that might actually change. But at the moment we shouldn't be trying to create a scenario where people are going to be terrified.”

The World Health Organization stated health risks were minimal as long as the ash stayed high in the air but that problems could occur if it fell to earth.

" People with chronic respiratory conditions such as asthma, emphysema or bronchitis could suffer irritation" the WHO said.

It said people should go indoors if they noticed irritation in their throat and lungs, a runny nose or itchy eyes.

Meanwhile, Irish airports may again be mostly shut if the ash returns. However, transatlantic flights seem safe, as the ash is not over the Atlantic. U.S flights were the only ones not affected yesterday by the volcanic ash.