Firefighters on Saddleworth Moor have faced a number of issues, including the weather and the presence of peat, as they battle to get the blaze under control.
- How did the fire start?
One of the first questions on people's lips, it is - at the moment - one of the most difficult to answer. The cause of the original fire - thought to be at Buckton Hill, Carrbrook - has not been established but fire chiefs said a detailed investigation would be launched at the appropriate time. During a long period of dry and hot weather, moorland fires are not uncommon. Police may also be asked to investigate whether arson is behind the initial blaze. However, a cause may never be known.
- What happened next?
The fire quickly took hold on Sunday, prompting the evacuation of 40 homes in the area. It has been burning ever since, swallowing an area speculated to be in excess of seven miles. Fire chiefs say it is the worst moorland fire in living memory to hit Saddleworth - and they expect to be there at least until Saturday.
- What are the contributory factors of the blaze?
The extended period of very hot and dry weather increases the potential for moorland fires. But the fact that there is a heavy concentration of highly combustible peat loaded under the surface is one of the main reasons why firefighters are continuing to tackle it.
- What is so special about peat?
It is an organic material, and it is reckoned it takes a year to produce 1mm. In other words, removing a metre of peat from the surface of the Earth would take a millennium to reproduce naturally. Fred Worrall, professor of environmental chemistry at Durham University, said the fact that peat is covered with heather makes it even more combustible. He said: "The firefighters will be putting out the flame - that's the dried shrub, the visual element - but the fire continues to burn underneath. It's like setting fire to your compost heap."
- How will the fire be put out?
Firefighters have used beaters, and a helicopter has been dropping water on to the fires. But the best-case scenario now is "persistent, light rain", Professor Worrall said. He added: "In an ideal situation you don't want heavy rain. The surface is completely damaged - a heavy downpour will wash away the surface towards the rivers and reservoirs. I don't think people realise how much damage there could be - if the fire has burned down, the fire will therefore have released years worth of carbon stored in the peat back into the atmosphere." The moorland is also a natural home to ground-nesting birds such as twites, a member of the finch family - it is not known how wildlife has been affected.
- Why was the fire so unusual?
The fact that it happened so late in the season is a troubling factor. Professor Worrall said: "We would normally expect these sorts of moorland fires to be earlier in the year, at least by the end of May or very early June. That is because normally by this time the heather is usually covered in leaves, it is moist, and so less susceptible to burning. That we've had a fire of this magnitude so late in the year is a real worry."