Geology and Soil Mechanics - Essay Example

Name : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Tutor :xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Title : Geology and Soil Mechanics Institution : xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Date :xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx @ 2010 Introduction Geology and Soil Mechanics This hand book displays the different types of rocks found Wales together with information on natural hazards that occur in Carmarthen Bay. The rocks can be observed over a wide area of Wales from the North to the South if a road was to transect the area. The Green Slate The first kinds of rock that can be observed in Wales are the Burlington slate or Green slate. They can be observed at Cumbria. It belongs to the Ordovician geological age. Its geological unit can be classified as Borrowdale Volcanic Group. It is about 450 to 460 million years old; Smith and Neville (1948). Geological Description: They form a bigger part of the Lake District especially the mountain areas. The Borrowdale volcanic group of rocks underwent a deformation during the Acadian orogeny. This was a time of great tectonic movements. Form that there came several types of metamorphic rock types. The green slates happen to be a product of that process. Originally they were laid down as volcaniclastic fine grained rocks. They were made from ash coming from the volcanic activities around the place. More deformation made them split into cleavage planes. They are suitable for making walls and roofs of buildings. They have been used for roofing since the 18th century; Smith and Neville (1948). . Figure 1a Figure 1 a shows the photograph of the green slate. Brenchley, Rawson (2006) Type of rock: Elland Flagstone or Yellow sandstone Area found: Yorkshire Geological Age: Carboniferous Geological Unit: “Pennine Coal Measures Group, Elland Flagstone Formation (about 310 million years old)” Geological Description: The name flagstone given to this rock comes from the thin beds that split into parallel flat slabs. They have fine grains with thin beds. They are formed from deposits coming fromalluvial streams together with river deltas. The sandstones split easily because of the mica mineral. The stone is important for roofing since it has thin slabs. It is also used for paving and making walls. In the 19th century the eland rock was mined for the provision of paving stone in London and elsewhere in England. Figure 2a Figure 2b Figure 2a and b above show the photomicrograph and the photograph for the yellow sandstone respectively. Brenchley, Rawson (2006) Rock type: Ancaster Stone or Yellow limestone Location: Lincolnshire Geological Age: Middle Jurassic Geological Unit: “Lincolnshire Limestone Formation (about 165-170 million years old)” Geological Description: Initially they accumulated in shallow shell banks in the sea. They are pale yellow in color. Originally they formed in seas in the tropics in ooid shoals and shell banks. In the middle Jurassic period they were the dominant stones in the central and southern part of England. They are also good in buiding and because of this they have been quarried so much. They also serve to make decorative carving and making walls. Figure 3a Figure 3b Figure 3a above shows a photomicrograph of the yellow limestone. Figure 3b shows a photograph of the stone. Brenchley, Rawson (2006) Rock type: Linby Stone or orange limestone Area observed: Nottinghamshire Geological Age: Permian Geological Unit: “Cadeby Formation; almost 260 million years old” Geological Description: It is found in Nottinghamshire and is useful for building. It is found laid in thin beds. It is made of limestone rich in magnesium or dolomite. It is the dominant and most common stone in the area for along time since the medieval times. Figure 4a Figure 4b Figure 4a and b above; A photomicrograph and photograph of the Linby stone observed in Nottinghamshire; Brenchley, Rawson (2006) Type of stone: Pennant Sandstone or Blue gray sandstone Area of origin: South Wales Geological Age: Carboniferous Geological Unit: “South Wales Coal Measures Group (about 305-310 million years old)” Geological Description: They occur in the coal fields of South Wales. They make a plateau feature on the tops of valleys. They occur in thick beds and are blue grey in color. They are hard and resistant. Their deposits came from fluvial channel systems that used to cover Gloucestershire and a big part of South Wales. It is an important stone for building in the South Wales area and beyond. Figure 5a Figure 5b Fig. 5a and b above shows a photomicrograph and photograph of the Pennant sandstone or blue grey sandstone as observed in South Wales. Brenchley, Rawson (2006) Type of rock: Berwyn Slate or blue grey slate Observation Area: North Wales Geological Age: Silurian Geological Unit: “Nantglyn Flags Formation (about 420-430 million years old)” Geological Description: The rock has fine grains. Initially it was made from deposits of salty mudstones of a dark color as well as laminated muddy siltstones. They were formed in deep water with in beds. The deposits occurred in a basin that occupied a big chunk of North and mid Wales in the Silurian. Deposits settled in the basin as turbidite flows. In the Caledonian orogeny they were disturbed and deformed. This deformation changed their structure form soft deposits in the basins to hard slate beds with a lot of cleavage as observed today.“These slates form part of the extensive Welsh slate belt which has been supplying slate for roofing worldwide since the late 18th century.” Smith and Neville (1948). Figure 10 a Figure 10 b Figure 10a and b above shows the North Wales Blue Grey slate. Brenchley, Rawson (2006) Natural hazards and coastal engineering works in Western Carmarthen Bay Carmarthen Bay refers to an inlet found on the coast of South Wales. On the coastline there are beaches like the Cefn Sidan sands and the Pendine sands. It has the Pembrokeshire National Park covering the bigger part of it. It has rivers like the Loughor, Taff, tywi and Gwendraeth flowing into the bay. Some of the towns found on the bay are Kidwelly, Pembrey, Laugharne among others. Carmathen Bay has been hit by natural hazards that disturb the normal activities of the place. Some natural hazards result from the fact that the bay is low lying and prone to rising sea levels. Therefore floods are some of the things that have been observed on the bay in the recent past. Natural hazards are being increased by the engineering operations carried out on the bay. These operations alter the shape of the land and geomorphology thus making it vulnerable to those hazards. The occurrence of natural hazards disturbs the normal flow of activities on the bay. For example floods are known to destroy structures and interfere with wildlife ecosystems in the national park found on the bay; Clifford, Hamman (1997). Other problems caused by engineering works on the coastline include massive erosion. Destruction of the natural structure of the rocks and soils results in loosely held soils and stones that are easily washed away. Engineering works along the coast were prompted by the need for increased commercial and residential premises. There is a lot of infrastructure on the edges of beaches. This call for defense facilities creation to protect the land from the raging sea waves; Clifford, Hamman (1997). References Bernard Smith, Thomas Neville George (1948).Geological Survey of Great Britain .British regional geology; North Wales Clifford Embleton, Christine Embleton-Hamann (1997).Geomorphological hazards of Europe Jan Otto Marius Broek,John Winter Webb (1973).Geography of Mankind. Amzon Publishers. New York. P. J. Brenchley, Peter Franklin Rawson – (2006).The geology of England and Wales Rendel Geotechnics,Great Britain. Dept.of the Environment (1993) Coastal planning and management. Oxford University. Read More