An Overview of the Geology of Britain An Overview of the Geology of Britain The very creation of Britain as an island is a represented, with Proterozoic rocks of fascinating story in itself resulting from hun- between 1,500 and 3,000 million years of age dreds of millions of years of tectonic activity sharing the island with much younger sedi- wherein land masses collided and split apart ments from the Palaeogene less than 60 mil- again as they moved across the surface of the lion years of age. This diversity is readily globe in their tectonic ballet. Even since apparent as one journeys around Britain, as Precambrian times, which ended 542 million has been discovered during the preparation of years ago, the various land masses have been this book. This section provides a brief over- pirouetting across the globe with areas which view, with the following sections providing a are now oceans variously covered by land and greater level of detail for specific areas of vice versa. The history of the Earth of course interest. reaches much further back to 4,600 million If we start in East Anglia and work our way years ago, but if we documented the various clockwise around Britain we shall discover tectonic events just since the Precambrian much of this interesting geological variation. period, we should have an interesting list. If On the eastern coasts of Norfolk, Suffolk and just one of these events had been different, if a Essex, the geology is quite young with the moving land mass had altered its course by just sedimentary layers being deposited primarily a few degrees, if a continental split had occurred within the Palaeogene period, less than 65 at a slightly different position, if the timings million years ago. This strata sweeps along had been slightly desynchronised, then Britain the northern shores of the Thames Estuary as we know it may not have been created at all. and extends westwards well past London. It Even much later on, if ice ages, glaciations and exists of shales, mudstones, sandstones, clays subsequent melts had not contrived to form the and of course chalk. Combinations and varia- North Sea and the English Channel, then there tions of these may be found throughout the would be no Britain as a separate entity. The area, with the chalk exposed at certain sites very existence of Britain is as a result of and clays and gravels at others. The coastlines random tectonic and climatic activity. Conse- tend to be relatively soft and vulnerable, espe- quently, Britain owes its existence as an island cially the eastern Norfolk coast whose cliffs as much to chance as anything else. And yet, of soft sandstones and mudstones are easily this island embodies a pocket history of much eroded giving cause for concern, especially of the aforementioned activity, nicely wrapped with the spectre of future rises in sea level to and presented in a beautiful little package. It is consider. indeed an island gem. On the northernmost Norfolk coast, as one Due to the aforementioned tectonic ballet, our looks towards Hunstanton, we find strata island gem contains remnants from land from the Cretaceous period laid down between masses we now know as North America and 65 and 142 million years ago. These include Europe as well as oceanic and arid desert sandstones and mudstones and the distinctive environments which were once situated in the red chalk to be found within the Hunstanton tropics. These have all been jumbled together cliffs. This Cretaceous swathe extends in a and fashioned by successive glaciations to south westerly direction down to the south produce our current distinctive land form. As coast where it skirts above the coastline adja- a consequence, we are blessed with a rich cent to the Isle of Wight and briefly touches variety of geology within a very small land the Dorset coast. From here it also extends mass. Similarly, a broad time period is eastward to cover Sussex and most of Kent, J. Ashbourn, Geological Landscapes of Britain, 19 DOI 10.1007/978-90-481-8861-1_2, © Springer Science+Business Media B.V. 2011 20 An Overview of the Geology of Britain excluding the north Kent coastline which ago. At Lyme Regis the beautiful limestone displays later strata. The southern part of this pavements and associated features have long coastline includes the distinctive white cliffs attracted fossil hunters as this area has pro- of Dover and those of the Seven Sisters fur- duced some of the most significant fossils ther to the west. These beautiful cliffs actually from the period. Ammonites and fossil consist of many layers, often separated visu- remains of small marine creatures are to be ally by thin seams of flint nodules, spaced found in abundance. Unfortunately, the adja- fairly regularly upon the exposed cliff faces. cent cliffs are somewhat unstable and the area These cliffs are also subject to erosion and has been prone to mudslides and partial cliff one can often find sizeable chunks of the collapse. Most recently, this activity has chalk which have been detached from the obscured certain parts of the beach where fos- main cliff and are being slowly eroded by sils were readily found. It is almost as though wave action. This south eastern section of the nature, having once presented us with such south coast nonetheless provides some inter- rich finds, is now burying them once again. esting variation, including pebble and shingle On the Dorset coast, we find several well beaches and a range of habitats atop the cliffs formed bays and some interesting features as one looks inland. such as Durdle Door, where the waves have Moving westwards along the south coast we etched a beautiful archway into the limestone enter the what has become known as the finger protruding out to sea. Within the adja- Jurassic Coast, with mudstones, sandstones cent bays to the east of Durdle Door, one can and limestones laid down during the Jurassic find similar fingers of rock stretching out to period between 142 and 205 million years sea at low tide. The bays themselves have Fig. 1 The chalk cliffs meet the sea at Seven Sisters some very interesting formations of limestone and Sidmouth, contrasting against the hues of and sandstone, occasionally exhibiting some the adjacent sea. While relatively soft in com- distinct folding and extreme angles of stratifi- position, these cliffs seem to be rather more cation. Clearly there has been some dramatic durable than those further along the coast to underlying geological activity to form the the east. They also exhibit some distinctive coastline we see today. The swathe of Jurassic layering in places which simply adds to the strata extends from the south coast in a north beauty of this coastline. An interesting excep- easterly direction to The Wash, skirting around tion may be found at Beer, where the coastal the Cretaceous strata at the coast around Hull, rocks are composed of chalk and gleam white before appearing again briefly in Yorkshire. In in the morning sun. On the adjacent beaches so doing, it cuts right across the lower there are many variations of pebble and sand Midlands. to be found including, at Budleigh Salterton, As we move further westward to the Devonshire the particularly distinctive large dense peb- 21 coast we find strata from the Devonian period bles which characterise the beach at that between 354 and 417 million years of age, point. These pebbles, unlike any others found considerably older than the Cretaceous rocks on the south coast, are composed of a hard found further east. These are mostly sand- quartzite material, similar to that of the stones and mudstones which occasionally Brittany rocks which are around 440 million exhibit a striking visual appearance with years of age. Speaking of pebbles, those at some beautiful burnt orange and red sand- Chesil beach, further eastward on the Dorset stone cliffs, such as those found at Exmouth coast, reach out to sea towards Portland in a An Overview of the Geology of Britain Fig. 2 The soft sandstone cliffs at Happisburgh on the Norfolk coast 22 An Overview of the Geology of Britain long spit well over 20 kilometres in length clay. The area contrasts notably with that which serves to protect the largest tidal lagoon further along to the west. in Britain. The Fleet lagoon forms a natural Inland from the south Devonshire coastline nature reserve within which many species we find the distinctive granite intrusion thrive and are effectively protected by the which is Dartmoor. Dartmoor rises up from pebble spit of Chesil beach. the surrounding area in a beautiful gently There are so many interesting features undulating plateau which is broken through along this stretch of coastline. Kimmeridge in many places by the granite tors. These tors gives its name to a distinctive Jurassic clay range in both size and texture, some like which may be found within the bay. The Haytor, becoming a favourite with rock clay is interspersed with limestone and climbers anxious to practice their skills upon there are some interesting limestone pave- these small scale ‘mountains’. A little further ments and spits reaching out to sea which north, Houndtor presents a subtly different render Kimmeridge Bay a most interesting picture with the granite appearing more rug- spot for those wishing to observe marine ged and twisted as though having taken a life in the shallows. The rocks are particu- tortuous path before finally breaking free at larly distinctive with yellows, browns, greys the surface. Each of the Dartmoor tors has its and some very dark mudstones providing a own special character however and indeed, colourful spectacle, interspersed by some the granite can assume a quite different equally interesting pebbles and overseen by appearance at various places across the the Kimmeridge cliffs with their distinctive moors.