the next 40 million years: Top up and drain off excess water several
times. Add new ingredients as they evolve.
sea-levels rise and fall repeatedly through the ages. Fresh ingredients
come and go. The motion of the swilling seas helps seabed sand
and mud ('sediment') to settle over their old bodies. As the years
pass the bitty sediment hardens under pressure into a rock-solid
pastry, preserving the remains beneath the sea-bed. The pastry
is made up of Hornton Stone (ironstone) and Blue Lias (clay and