How quickly (or slowly) does it take for a fossil to be formed?
Sometimes very quickly, sometimes very slowly. Imagine 125 Million years ago, when dinosaurs were wandering about on a land mass which we now call the Isle of Wight; all around is a flat marshy land, dissected by rivers, streams and ponds. Muddy areas surround the waterways, where dinosaurs can trample and roll around leaving body impressions and lots of footprints. Occasionally a dinosaur dies in the mud, or is swept in by a flood. After the flesh decays, the bones begin to sink into the mud. Very quickly (sometimes in a matter of weeks) bacteria aided by complex chemical conditions allow the replacement of bone with black sulphurous deposits, (pick up a rock which has been lying on the beach for a few weeks and look for the black staining underneath). This is the beginning of the fossilization process. Years later, after layers of mud and sand have piled on top of the dinosaur bones, they may crack under pressure. The cracks allow the formation of water-borne minerals such as calcite
