Photographs taken from the air are particularly useful to archaeologists and not just because the view gives us a different perspective of a site or the landscape. At different seasons and at varying times of the day, much information can be learned about sites when they are viewed from the air.

'Anaerobic' means 'without air'. In such conditions - such as waterlogging - where there is insufficient oxygen for bacterial and fungal growth, the normal rotting processes do not take place. So all the things made of wood, leather, straw and so on that archaeologists love to find, but which, in our climate, usually rot away very quickly, remain well preserved.

Environmental archaeology is concerned with seeds, pollen, snails, beetles and other insects, bones and so on, which can be used to reconstruct what the environment looked like in the past.