Heights above Mean Sea Level.
Mountain Tops - Mynydd James 540m (1771feet); Gwastad 553m (1814feet).
Coity 581m (1986feet); Cefn Coch 574m (1883feet); Cock & Chick 430M (410feet).
Other Points - West Bank 330M (1082feet); Reservoir 400M (1115feet); Pen-y-bont 260M (853feet).

Ice age - Wales was just about the most southerly point in the British Isles to have experienced an Ice Age that covered the mountain tops and produced Glaciers. It was the forming and melting of these Glaciers which created the valleys of Cwmtillery and South Wales. Stretching North to South, from the Heads of the Valleys Road to the M4 Motorway, these steep sided "U" shaped valleys with lofty gritstone edges, were carved out nearly 10,000 years ago. Yet to the geologist these are the youth of the district, containing the youngest rocks and are generally classified as the coal mining region of South Wales.

Glaciers - Glaciers begin to form when snow remains in the same area year-round. Each year, a new layer of snow bury and compress the previous layers. This compression forces the snow to re-crystallize, forming small grains of ice. Gradually these grains grow larger and the air pockets between the grains get smaller causing the snow to increase in density. In a short time (within a year of two) depending on temperature and volume, the snow turns into firn (an intermediate state between snow and glacier ice). Once the mass of compressed ice reaches a critical thickness, it becomes so heavy that it begins to deform and move. The sheer girth of the ice, combined with gravity's influence, causes glaciers to flow very slowly. As they move they transport material and carve away at the land beneath. Acting as an enormous sweeping brush, the ice erodes the land surface, carrying broken rocks and soil debris far from their place of origin. Over hundreds, or even thousands of years, this ice will totally change the landscape, leaving these "U" shaped valleys behind.

Coal - Coal is a fossil fuel created from the remains of plants that lived and died between 100 million to 400 million years ago. Due to the quantity found in Cwmtillery, it would indicate the mass of swampy woodlands and other vegetation which once thrived here after the Ice Age. The energy we get from coal today comes from the energy that plants absorbed from the sun, millions of years ago. The plants store energy from the sun through a process called photosynthesis and after the plants die, this energy is released again as the plants decay. The dead plant matter which fell, or was washed into the swampy water, must have accumulated here and over the years. This accumulation would cause a thick layer of dead plants to lie decaying at the bottom of these swamps. Over time, and with a surface and climate change, more water and dirt would wash in, halting the plants decaying process and locking in the energy stored. Under heat and pressure, this plant matter underwent chemical and physical changes, pushing out oxygen and leaving rich hydrocarbon deposits. Over the years this process would repeat itself causing new layers of hydrocarbon deposits to develop into what we now call coal seams. What once had been plants gradually turned into coal, which is classified as a non-renewable energy source because it takes millions of years to form.

Coal Types - Coal is generally classified by what is known as "rank" and is based on the degree of transformation of the original plant material to carbon. The ranks of coals, from those with the least carbon to those with the most carbon, are lignite, sub-bituminous, bituminous and anthracite. In addition to carbon, coals contain hydrogen, oxygen, nitrogen and varying amounts of sulphur. High-rank coals are high in carbon and therefore heat value, but low in hydrogen and oxygen. Low-rank coals are low in carbon but high in hydrogen and oxygen content Sub-bituminous coal, bituminous coal and anthracite are together known as black coal. Bituminous coal being the type of coal excavated here and in the past used for the hundreds of coke burning furnaces in South Wales. As the decline in the coke furnaces came, the coal was required in other areas such as steam locomotives, industry and housing.

Coal Seams - Ranging in thickness from a fraction of an inch to several feet have been excavated at Cwmtillery, Pen y bont, The Gray and many other smaller levels throughout the valley. All of these seams may represent hundreds or even thousands of years of plant growth.

Eiled....Big Vein.... Threequarter....Top Black....Lower Black....Meadow, ....Oldcoal....Garw coal seams

Coal Mining - Coal is mined by two main methods - surface or strip mining and underground or deep mining. The choice of method is largely determined by the geology of the coal deposit. At Cwmtillery colliery, the deep mining method was used. This started by sinking (digging) a shaft vertically down to the coal seam named "Old Coal Seam" 238.6 metres below ground level. From the main shaft, tunnels were made at angles of approx 20 degrees back towards the surface, intersecting other coal seams. From these tunnels further tunnels were made, cutting along the seams of coal found. The Garw seam was found below the main shaft and tunnels were made downwards at an angle until the seam was located.

Extracting the Coal - Main tunnels were bored into the coal seam, with another working tunnel intersecting these main tunnels. This gave access to the coal seam and provided the required air flow underground. As the first section of coal was removed, the main tunnels would be advanced further into the coal seam and the next section of coal removed. In order to support the now exposed rocks above, wooden pillars were used in the early days of coal mining and would be positioned at regular intervals behind the working miners. ( Left shows a view looking down on top of the working coal seam. As excavation of the seam continued to move forward, the area supported by these wooden pillars increased, the weight above would grow to such proportion the wooden pillars farthest away would finally collapse behind the working miners. This moving forward, removing coal sections and the collapsing of the worked area behind, would continue throughout the coal seam. It must be like trying to remove the cream layer from a sponge cake without touching the cake. The coal seam was removed in the early days with pick and shovel, as a line of miners stood 8 yards apart along the length of the coal being removed. The coal would then be removed by pony and tram. All the coal would be trammed to the bottom of the pit shaft and winched up in lifts. As modern technology moved in, the wooden supports were replaced by hydraulic pillars, as the excavation moved forward the pressure could be reduced in the jacks, thus causing a controlled collapsing of the worked area behind the miners. Also huge cutters replaced the pick and shovel and conveyor belt systems were used to carry this black gold back to the surface.
In the mid 80s a multi million pound extensive land reclamation took place throughout the valley, it used the black mountain of coal waste on the Mynydd James mountain and importing top soil. Filling in the area between the lower lake and reservoir, also from the site of the Cwmtillery colliery down the valley to the Gray. Thousands of trees and bushes where planted and later a playing field in the middle of the valley constructed, all with the aim to restore the valleys natural beauty.