Sychryd is a short river which rises to the south of the Geopark -in fact the only one to do so - and heads through a deep wooded gorge for a meeting with the Afon Mellte near Dinas Rock.

The most spectacular part of its course, immediately below Craig-y-Ddinas is guided by the fault zone of the Neath Disturbance where, as Sgydau Sychryd, it cascades though a narrow slot between rock walls. The strongly folded limestones of Bwa Maen tower above its waters just below the cascades.

Spectacular geology

There are few places in South Wales where the geological upheavals of the past are more strikingly displayed than along the course of the Sychryd. The main gorge section has been carved out by the river along the Dinas Fault, where movement of the rocks on either side has fractured a broad band of rocks and made them more prone to erosion by water. There are at least a couple more parallel faults to the north of Dinas Rock which together with associated folds in the rocks are collectively known as the Neath Disturbance. The Dinas Fault Zone is effectively the entire width between the sheer walls of Dinas Rock and Bwa Maen which contains a multiplicity of movement planes - surfaces which have slid past each other in the past.

The great prow of rock known as Bwa Maen (literally the 'stone arch') is an extraordinary tight folded block of Carboniferous Limestone. It can best be seen in winter from near the end of the Sychryd all-ability trail when the vegetation has died back.

The Neath Disturbance is one of several such ancient weaknesses in the Earth's crust in South Wales. It can be traced southwest down the Vale of Neath to Swansea Bay and northeast through Moel Penderyn, Cwm Cadlan and on along the valley north of Sugar Loaf to die out somewhere just to the south of Hereford. It was probably active during both the Caledonian Orogeny and the later Variscan Orogeny - each time it move, an earthquake shook the region.

Industrial legacy

Step back in time a few decades and this place was a hive of industry. Thousands of tons of solid rock were mined from either side of the Sychryd Gorge leaving a honeycomb of caverns beneath its wooded sides. Walkers exploring its steeply wooded slopes today may come across some of the many entrances to these caverns.

Do not be tempted to enter the mines as they are hazardous - there are steep drops in the dark whilst parts are now flooded and there have been roof-falls in some places.

The miners were after the 'basal grit' of the Millstone Grit series of rocks - a particularly hard band of rock we know today as the 'Twrch Sandstone' but they would have referred to it as the 'silica rock' for that is what it was - over 98% pure silica (silicon dioxide or Si02) otherwise known as quartz.  Once it had been crushed to powder and re-shaped as bricks it would be fired in a kiln to form refractory bricks or firebricks used to line the furnaces of the iron and steel smelters of industrial South Wales. These bricks came to be known as 'Dinas Bricks' and, in at least one of the countries to which these bricks were exported - Russia -  the word 'dinas' came to mean 'firebrick'.

An aerial ropeway stretched high over the Sychryd gorge carrying the lumps of mined rock down to the Dinas Rock from where they were transported to the brickworks at Pontwalby. A system of tramways was also in use in the area to transport the mined material.A steep ramp supported on iron pillars linked tramways above and below the main Sychryd cascade. The stumps of these pillars are still visible today.

Ancient boundary

The river forms a part of the boundary between the modern day local government areas of Powys and Rhondda Cynon Taf. Before 1974 this was the historic boundary between the counties of Brecknockshire to the north and Glamorgan to the south. In even earlier times it marked the edge of the kingdoms of Brycheiniog and Glywysing (later Morgannwg). Since 1957 it has also served as the boundary of the Brecon Beacons National Park and, since 2005 has been the Fforest Fawr Geopark boundary too.

Enjoy it!

The Sychryd All-ability Trail follows the lower reaches of the river from Dinas Rock car park as far as Bwa Maen and Sgydau Sychryd.  The trail follows the course of a former tramway which once served the Dinas Silica Mine.