Avon - Rocks
The gorge cuts through a ridge mainly of limestone, with some sandstone. This particular ridge runs from Clifton to Clevedon, 10 miles (16 km) away on the Bristol Channel coast, although limestone is found throughout the Bristol area. The fossil shells and corals indicate that the limestone formed in shallow tropical seas in the Carboniferous, 350 million years ago. For a long time it was unclear what caused the Avon to cut through the limestone ridge, rather than run south west through the Ashton Vale towards Weston-super-Mare. However, Bristol was at the southern edge of glaciation during the last ice age, and it has been suggested that ice blocked the river's natural route through Ashton Vale to the west. At the Clifton Suspension Bridge the Gorge is more than 700 feet (213 m) wide and 300 feet (91 m) deep.
You can read more about the history of the Gorge at the Wiki
The Geocache
At the posted coordinates there is a wealth of information about the geology of the Avon Gorge. The question is- How many millions of years ago did the mountainous desert begin? Answer = ABC
The final hide is located a short stroll away at N 51° 28.1(7-A)B W 002° 37.8C4
Now is a great time to continue and do Avon - Goats and Hhamburger Combo Earth
This geocache was placed with the kind permission of Bristol City Council and Natural England