Locations

1 second 2 seconds 3 seconds 4 seconds 5 seconds 6 seconds 7 seconds 8 seconds 9 seconds 10 seconds 11 seconds 12 seconds 13 seconds 14 seconds 15 seconds 20 seconds delay, loading photo...          Hertfordshire Puddingstone in the churchyard: a conglomerate of flint pebbles in a silica matrix at the base of the Reading Beds, which were deposited in the Eocene (56 million years ago). The pebbles, eroded from the chalk, were rounded and sorted by water action (similar to pebble beaches). During a brief period when the sea retreated in a semi-arid climate, capillary action brought dissolved silica from underlying rocks. The water evaporated leaving the silica which hardened around the pebbles.  Author: J Harrison,