Earth Heritage - Geology The Isle of Wight AONB has a complex geology within a small land area, and is considered to be of outstanding geological significance. Since the early nineteenth century, the excellence of the rocks and fossils on the Isle of Wight have been celebrated, and the Island continues to attract professional and amateur enthusiasts. The oldest rock formations on the Isle of Wight are from the Cretaceous period; the earliest of these are the Wealden Group, which were formed between 127 and 121 million years ago. Formed by the gradual deposit of fine silts, sands and mud in an area that was at that time a broad river valley subject to periods of drought and high rainfall, this formation is rich in fossil remains. In particular there are fossilised bones, petrified tree deposits and footprints of herbivorous dinosaurs such as the Iguanodon. Particularly good examples of this geology can be seen where it is exposed on the coast at Brook Bay (Grid Ref: SZ385834) and Yaverland (Grid Ref: SZ612850). When occurring inland it is associated with heavier soils, and has traditionally been used as pasture. The next part of the geological sequence occurred between 121 and 100 million years ago. Formed when the river bed gradually flooded and became a shallow sea, the Lower Greensand, Gault and Upper Greensand are a result. Lower Greensand is the underlying geology of much of the southern part of the Island, and the light sandy soils over this rock formation provide some of the best and most fertile land on the Isle of Wight. High terraced cliffs occur where this rock meets the sea, with good examples being found at Whale Chine (Grid Ref: SZ468783) and Red Cliff (Grid Ref: SZ618854). Gault and Upper Greensand occur together close to the central chalk ridge and southern downs. Gault is a dark grey clay (known locally as Blue Slipper) and Upper Greensand is a pale grey sandstone. The weakness of the clay and the solid nature of the sandstone, have led to some of the most spectacular landslips in Europe. The final part of the Cretaceous period saw the formation of the Lower and Upper Chalk. Grey and white limestone formed in deep seas from microscopic algal remains. Irregular flint nodules occur in the Upper Chalk; these were used by early inhabitants of the Isle of Wight to make tools and weapons. Forming the central ridge and a plateau area of the southern downs, Chalk is an important landscape feature of the Island. The tall white cliffs at Culver (Grid Ref: SZ633853) and the sea stacks at the Needles (Grid Ref: SZ290849) are a dramatic visual element of the character of the AONB. The Cretaceous period ended around 65 million years ago, with the gradual retreat of the sea and the gentle buckling of the rocks by earth movements. A long period of erosion then followed between 65 and 55 million years ago. Rivers and the sea reinvaded the land, and deposited multicoloured sands and clays (Palaeocene and Eocene), examples of which can be seen at Alum Bay (Grid Ref: SZ303854). Red, grey and green clays and sands were deposited in rivers, swamps and estuaries around 30 million years ago (Oligocene) leading to the creation of the heavier soils of the north of the Isle of Wight. The retreat of the sea and a dramatic buckling of the rock sequence caused by the formation of the modern day Alps, moved many layers of rock from lying horizontally to the near vertical position we see today. Around 2 million years ago, the climate began a series of relatively rapid changes. At times of low temperature, the climate was similar to modern day arctic Canada with glaciers forming in much of Britain, and sea levels being so low that the English Channel was dry land. Lower seas caused the river valleys to deepen. In interglacial periods the temperature was similar, if not warmer, to that of today, causing sea level rise and the flooding of deepened valleys. Around 210,000 years ago, the present interglacial period began; temperatures increased and sea levels gradually rose. Around 6,000 years ago, the final inundation of the Solent is thought to have taken place, creating our island status. Since then future sea level changes, coastal erosion and soil formation, have all helped to produce the Isle of Wight AONB that we value today. Many sites within the AONB are important for their geology or geomorphologic features either at a local, regional, national or international scale, and are designated accordingly. Back to top The geology of the AONB continues to provide an important finite resource for minerals such as chalk, gravel, clay and sand. The Isle of Wight Council, as Mineral Planning Authority, details current and expected extraction, and sets out policies that seek to safeguard sites of importance for geology, geomorphology, nature conservation, archaeology, historic environment and landscape value. Back to top Soil is a basic, limited resource that is essential for many human activities. It includes topsoil and subsoil to the depth of at least 1 metre. The biological, physical and chemical characteristics of soil need to be protected for it to perform its important functions, including the production of food, raw materials and energy. Soils provide a filtering and buffering action to protect water and the food chain from potential pollutants; they help to maintain gene pools and wildlife populations; and often cover historic and archaeological sites containing artifacts and historical indicators such as pollen. All soils need to be managed sustainably for the long term. Water is essential to life. The Chalk geology of much of the Island is an aquifer collecting and storing rainwater. Abstraction rates and land use can have a major impact on the quality and quantity of water available as a physical resource. Some species and habitats are particularly sensitive to water levels and to pollutants, with small changes having a marked impact on populations and ecosystems. Sustainable management of this important resource is essential to the health of the environment. Back to top The Isle of Wight is well known for its mild climate and clean air. An important resource for the health of people and wildlife, its protection is essential. Land use practices, burning of materials, and greenhouse gas emissons, all have an impact on the quality of this resource. The way in which the sea shapes the coastline can easily be seen in the habitats and landscapes of the Isle of Wight AONB. Eroding coastlines also threaten land and property, and the development of a Shoreline Management Plan is key in balancing the social, economic and environmental factors for sustainable management. Much of the coastline within the AONB is additionally defined as Heritage Coast in recognition of its scenic beauty and wildlife value, a direct result of the continuation of coastal processes. | 
