It is a little surprising that in spite of the relatively high standard of excavation techniques current in Britain today so little attention has been paid by practical excavators to the processes of formation of the sites which they dig.

All of us recognize, of course, that a site consists of a sequence of deposits, some formed deliberately and usually rapidly by man, and others more slowly by nature; and that some processes of formation, such as erosion and filling by the plough, are still continuing today. But there seems to be a widespread assumption (though it is difficult to be sure of this, since such things are seldom discussed) that once a constituent layer of a site has been formed, and sealed by another layer above it, it becomes immediately fossilized and remains unchanged until examined by the excavator, perhaps several millennia later. It is equally widely supposed that once an object, large or small, has come to rest in or upon a deposit it will remain in that position for all time. In short, the tacit assumption is that once formed the nexus of finds and deposits which constitutes a site is almost wholly static, and that change, if it occurs at all, occurs only at the surface.