GEOLOGY OF ENGLAND Rocks and Landscape
THE MALVERNS
The Malvern Hills are a range of hills in the English counties of Worcestershire, Herefordshire and a small area of northern Gloucestershire, dominating the surrounding countryside and the towns and villages of the district of Malvern. The highest summit of the hills affords a panorama of the Severn valley with the hills of Herefordshire and the Welsh mountains, parts of thirteen counties, the Bristol Channel, and the cathedrals of Worcester, Gloucester and Hereford. The Hills run north/south for about 13 km (8 miles), in between Great Malvern and the village of Colwall, and overlook the River Severn valley to the east, with the Cotswolds beyond. The highest point of the hills is the Worcestershire Beacon at 425 metres (1,394 ft) above sea level.
The Malvern Hills are formed of some of the most ancient rocks in England, mostly igneous and metamorphic rocks from the late Precambrian, known as the Uriconian, which are around 680 million years old. The Malvern Line is the name applied to a north-south aligned lineament which runs through the Malvern Hills and extends southwards towards Bristol and northwards past Kidderminster. It consists of a series of faults and folds which have the effect of bringing old Malvernian rocks to the surface. Being largely hard igneous rocks, they have resisted erosion better than those of the surrounding countryside and result in a striking line of hills of which the Malvern Hills are the most impressive. This line is considered to mark the edge of two terranes – two once separate fragments of the Earth's crust now joined as one – the Wrekin Terrane to the west and the Charnwood Terrane to the east. The main face of Gullet Quarry shows a cross-section through the Precambrian rock and exhibits many rock types including diorite, granite, gneiss, schist, pegmatite and dolerite. The evidence of the complex history of earth movements which formed the Hills can be seen by multiple joints, fractures, faults and shears, which make identifying changes in rock types difficult. Mineral deposits such as haematite, calcite and epidote can be seen within these features. There is a tiny, man-made cave near the ridge of the hills called Clutter's Cave (or Giant's Cave).The cave has been excavated into pillow lavas. Some of the rounded 'pillow' shapes are still visible around the entrance to the cave. The quality of Malvern water is attributable to its source. The rocks are characterised by low porosity and high secondary permeability via fissures. [ Malvern water is rainwater and snow meltwater that percolates through fissures created by the pressures of tectonic movements about 300 million years ago when advancing sedimentary layers of Silurian shale and limestone were pushed into and under older Precambrian rock. When the fissures are saturated, a water table forms and the water emerges as springs around the fault lines between the strata.
The Cotswolds This is an area in south central England containing the Cotswold Hills, a range of rolling hills which rise from the meadows of the upper Thames to an escarpment, known as the Cotswold Edge, above the Severn Valley and Evesham Vale. The Cotswolds is roughly 25 miles (40 km) across and 90 miles (145 km) long, stretching south-west from just south of Stratford-upon-Avon to just south of Bath. It lies across the boundaries of several English counties; mainly Gloucestershire and Oxfordshire, but also parts of Wiltshire, Somerset, Worcestershire, and Warwickshire. The highest point of the region is Cleeve Hill at 1,083 ft (330 m), just to the north of Cheltenham. This area is defined by the bedrock of Jurassic limestone that creates a type of grassland habitat rare in the U.K. and that is quarried for the golden coloured Cotswold stone: a yellow oolitic Jurassic limestone, rich in fossils, particularly of fossilised sea urchins. When weathered, the colour of buildings made or faced with this stone is often described as honey or golden. The stone varies in colour from north to south, being honey coloured in the north and north east of the region, as shown in Cotswold villages such as Stanton and Broadway; golden coloured in the central and southern areas, as shown in Dursley and Cirencester; and pearly white in Bath.
The rock outcrops at places on the Cotswold Edge; small quarries are common. The exposures are rarely sufficiently compact to be good for rock-climbing. However, an exception is Castle Rock, on Cleeve Hill, above Bishop's Cleeve, near Cheltenham. There is evidence of Neolithic settlement from burial chambers on Cotswold Edge, and there are remains of Bronze and Iron Age forts. Later the Romans built villas, such as at Chedworth, settlements such as Gloucester, and paved the Celtic path later known as Fosse Way. During the Middle Ages, the area became prosperous from the wool trade -indeed the name is usually attributed the meaning, sheep enclosure in rolling hillsides- and large "wool churches" were built. The area remains affluent. Typical Cotswold towns are Burford, Chipping Norton, Cirencester, Moreton-in-Marsh and Stow-on-the-Wold. The Cotswold town of Chipping Campden is notable for being the home of the Arts and Crafts movement, founded by William Morris at the end of the 19th and beginning of the 20th centuries.
Coity Mountain (Coety Mountain, Welsh: Mynydd Coety) It is a flat-topped mountain in the South Wales Valleys, between Blaenavon and Abertillery. The highest points of both Torfaen and Blaenau Gwent unitary authorities are at the summit of Coity Mountain. The summit is also known as Twyn Ffynhonnau Goerion. Some 2 km (1 mi) to the southeast lies a major subsidiary top of the hill, Mynydd Varteg Fawr (549m). Other notable tops include those of Mulfran (524m) (Welsh for cormorant, pronounced 'me-al-vran') which overlooks the town of Brynmawr and Mynydd James immediately east of the town of Blaina. Much of the mountain, including the summit is included in the Blaenavon Industrial Landscape World Heritage Site, and a labyrinth of coal mines, including Big Pit National Coal Museum, lies under the mountain.
The hill is formed from a succession of Carboniferous age sandstones and mudstones, notably the Pennant Sandstone, outcrops of which occur in places around the margins of its plateaulike top. The stone has been worked in places for building stone and a number of abandoned small quarries may be seen. The lower slopes of the hill are in the Coal Measures and have been intensively worked for coal with considerable areas of landscaped opencast workings evident along its northeastern side. Coity Mountain is likely to have stood above the ice during the last ice age as, unlike in surrounding valleys, there is no glacial till to be found on its slopes. There are areas of peat and accumulations of head and many small landslips adorn its steeper slopes…
Blaenavon, Torfaen Blaenavon during 1798-99 was enthusiastically described as an opulent and increasing establishment, which was surrounded with heaps of ore, coal and limestone. The reason for the growth of Blaenavon from a rural to an industrial community lay in the rich mineral deposits found in the surrounding area, which outcropped at the surface making extraction a relatively cheap process. The iron works demanded a skilled and permanent labour force, which the Eastern Valley of Monmouthshire lacked. Previous iron works at nearby Pontypool, for instance, had relied on charcoal and water. The nature of the work introduced to Blaenavon was different. The changes involved the coal-using technology and the application of steam power, not used until that time in the Eastern Valley. Skilled workers came mainly from West Wales, Staffordshire, Gloucestershire, Herefordshire, Somerset and Ireland. Blaenavon Ironworks was the first to be designed as a multi-furnace site from the outset[, with three furnaces, calcining kilns, cottages, and a company shop. The ironworks was of crucial importance in the development of the ability to use cheap, low quality, high sulphur iron ores worldwide. It was the site of the experiments by Sidney Gilchrist Thomas and his cousin Percy Gilchrist that led to "the basic steel process" or "GilchristThomas process�. Two new furnaces were added and in 1804 a forge was constructed in nearby Cwmavon.
http://www.glosgeotrust.org.uk/cots_geology.shtml http://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/ home.html?src=topNav
LEWISIAN GNEISS
The Lewisian complex or Lewisian Gneiss is a suite of Precambrian metamorphic rocks that outcrop in the northwestern part of Scotland, forming part of the Hebridean Terrane. These rocks are of Archaean and Paleoproterozoic age, ranging from 3.0–1.7 Ga. They form the basement on which the Torridonian and Moine Supergroup sediments were deposited. The Lewisian consists mainly of granitic gneisses with a minor amount of supracrustal rocks. Rocks of the Lewisian complex were caught up in the Caledonian orogeny, appearing in the hanging walls of many of the thrust faults formed during the late stages of this tectonic event.
https://www.google.es/search?q=lewisian+gneiss&client=safari&rls=en&tbm=isch&tbo=u&source=univ&sa=X&ei=XAZcVKWVJyv7AbCl4G4Cg&ved=0CC8QsAQ&biw=1280&bih=517 http://www.bgs.ac.uk/research/highlights/2011/menofrock.htmlhttp://www.bgs.ac.uk/research/highlights/2011/menofrock.html