June 11th, 2007

In the morning we met at Cwm Porth caves for a caving session (SN928124). Our cave leader was Garry a CIC holder (Cave Instructor Certificate) who works on the cave rescue team. We spent several hours down the caves exploring and learning about the geology.

The caves are formed from Carboniforous Limestone - a rock formed some 350 million years ago from crustacious species in tropical conditions which appear in this part of the world due to the movement of tectonic plates. Splits can be see in the rock in various places and it is these cracks and fissures that eventually form the tunnels in the caves after being eroded by carbonic acid. Carbonic acid is formed when rain falling in the locality absorbs carbon monioxide from the air creating a mild carbonic acid solution. The cracks and fissures can be initially created through tectonic plate movement or by the pull of the moons gravity.

 Two interesting routes/activites in the cave for groups where the ‘toilet’ and the ‘washing machine’. There was also a route called the ‘toothpaste tube’ which could not be used as it has dried up in recent years despite efforts to dam it to keep the water at a suitable level. Another interesting feature was ‘the white horse’ - a horse shaped patch of Calcite streaking near the cave enterance. The cave is popular with groups as you are never very far from the cave enterance and becasue it floods ever year it receives a ‘clean out’ and the cave enterance is also within easy walking distance of the car park, however the cave can become very overcrowded at times because of these factors.

In the afternoon me, Jon and the two work experience boys went to look at the waterfalls in Clun Gwyn. This is the first waterfall on the Afon Mellte which later downstream disappears underground into Porth yr Ogof cave system.