Actually, you're all wrong. Silbury straddles an area of unique geology. Deep delow the surface there is small fissure in the Earth's crust. Directly above this fissure is an underground lake and above that is the crumbly chalk bedrock. Water leaks very slowly from the lake into the fissure where it is superheated by the hot rocks and rises back to the surface of the lake as steam. Over many years, the action of the steam on the chalk turns it into a thick slurry.
Once every 800 years or so, the pressure builds to such an extent that an eruption occurs throwing tons of chalk up to the surface. The first eruption was in 2600 BC and there have been two others since then. Each has deposited a new layer of chalk and gradually created the almost perfect conical shape of the hill as we know it today.
This multi-layered structure has even caused some archaeologists to believe that the hill was man-made. To be fair, they were encouraged in this belief by the fact that ancient people were so impressed by the hill that it became a focal point for their megalithic building. The stone circle at nearby Avebury illustrates their preoccupation with the roundness of the hill, which they emulated in many of their structures.
The hill has aparently been dormant for almost 1000 years, the longest period in its history. but scientists believe that the collapse of the summit is a clear indication that another eruption is imminent. A spokesman from English Heritage declined to comment, but we have learned from other sources that EH have put their plans to repair the hill on hold for an indefinite period. Apparently, the hill is considered too dangerous for further work to be carried out. Members of the public are being deterred from visiting the hill by a temporary fence erected for their own safety.
;o))
