GEOLOGY OF TORBAY
Torbay is noted for its fine scenery, especially along the coast. This is mainly due to the great mixture of different types of rocks which can be found in the area, and the things that have happened to them in the past.
Many of the types of rocks in the area were formed by the laying down or deposition of small pieces of material or sediment. This sediment was carried in water or by the wind. When it was deposited it hardened and formed layers of rock, one on top of another.
The first, and oldest, group in the area is made up of rocks originally laid down underneath the sea. They are collecively known as the 'Devonian1 group. It includes Slates, Limestones and Tuffs. Each of these rock types was made from a different kind of sediment; slate is mud which has been turned to stone, limestone is the compressed material from old coral reefs and tuffs are the cooled and compressed ash from a volcano.Each of these rock types was laid down during a separate period and form a sequence in time.
The second, and younger, group was also made from sediments, but have built up on a land surface. At the time of their formation Torbay was part of a large desert area. Erosion of the bedrocks due to weathering produced a wide range of sediment. The sandstones that were formed are commonly red in colour and give the soil and beaches of the Bay their rich colour today. Unlike the first group the different rock types were not formed at different times. There are two main types; 'Breccia', which was formed by large, angular fragments held in a mixture of sand, silt and clay, and 'Conglomerates', which were formed from a similar mixture carrying rounded fragments. One very important difference between the two groups is .that the first, or Devonian, group was affected by a period of violent earth movements about 300 million years ago. This, was the period during which many of todays mountains were formed, and the origonal layers of rock were greatly folded and fractured. The second, or Permian, group were not formed until after the great disturbances and consequently show little breakage and only slight tilting.
The Devonian group was given its name because these types of rock were first described in Devon, in 1839. Most of the different types can be found 'outcropping1 in Torbay today.
On top of these 'bedrocks' other sediments have been laid down in recent times to produce another group of rock types. The sediments which formed these later rocks were deposited by the sea or left behind as the vast ice sheets, which periodically covered much of Britain during the last 1.5 million years, melted. They are of great interest today for two reasons; the raised beach deposits give information on the sea levels in times past, whilst the Ice age sediments contain many fascinating fossil remains of the animals living in the area during-the period.
The melting of the ice sheets to the north at the end of the last Ice age caused quite spectacular rises in the level of the sea. The raised beach deposits are recognisable today as well-defined layers of sand and silt, and gravel which is well rounded after its movements in the sea. These deposits often contain the fossil remains of many forms of marine life, giving present-day scientists a means of telling the age of such deposits. In some parts the deposits smothered forests and many fragments of fossil vegetable matter and animal bones have been washed ashore around the Bay.
The type of material laid down inland following the melting of the ice sheets depended greatly on the bedrock and is thus very variable. If it formed over an area of slate, for example, it would be made up of broken and weathered fragments of slate held in a mixture of clay, silt and sand. If however it developed in an area of sandstone it would be difficult to distinguish from weathered sandstone or breccia.
The Torquay limestone is the host of a great many caverns and cave systems, formed by the dissolution of the carbonate rocks by rainwater. Many of the surface deposits formed in the last 1.5 million years have found their way into the cave systems and partially or completely filled the open passages today. The deposits have also buried and preserved the remains of the animals and people who sheltered and died in the caves in the past. These remains have slowly come to light in the past 150 years due to the careful work of dedicated explorers and archaeologists.
