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Moel Yr Ogof
Moel yr Ogof is a summit in Snowdonia. It is a subsidiary summit of Moel Hebog and a sister peak to the lower Moel Lefn. There is an asbestos trial mine located on the summit. A small seam of white asbestos was discovered however insufficient amounts to commercially mine. Geology The summit of Moel yr Ogof is composed of a brecciated rhyolite, diagnostic of gravitational collapse in a rhyolite dome. Surrounding the crown of the mount is a geological unit consisting of alternating bands, of varying thickness, of pillow basalts and a green/grey sandstone that is of mafic origin, potentially derived from the pillow basalt itself. The pillow basalt is relatively well preserved in places, where devitrification rims clearly outline the individual pillows. It is composed of dark green/black, very fine crystalline, basaltic rock, which has weathered to a dark red/brown colouration due to the presence of iron minerals. The sandstone member of the unit is a pale green/grey, fine to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moel Hebog
Moel Hebog (Welsh for ''Bare Hill of the Hawk'') is a mountain in Snowdonia, north Wales which dominates the view west from the village of Beddgelert. It gives name to a whole range of peaks in the north-western corner of Snowdonia, which include the Nantlle Ridge and Mynydd Mawr. From that side, Moel Hebog has a rocky face with a distinctive pointed summit, although from other sides, it appears more rounded. The exposed rock means that it is often visited by students of geology. Much of the mountain consists of welded, fiamme rich rhyolitic tuff. It is often climbed from Beddgelert and it can be combined with the nearby mountains of Moel yr Ogof and Moel Lefn for a longer walk. This route, however, does involve some easy scrambling. On Moel yr Ogof can be found Owain Glyndŵr's Cave. The view of Moel Hebog and Llyn Gwynant from the north near Snowdon is one of the most photographed in Snowdonia. A late Bronze Age shield was found in a bog near Moel Hebog in 1784. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar. Mafic materials can also be described as ferromagnesian. History The term ''mafic'' is a portmanteau of "magnesium" and "ferric" and was coined by Charles Whitman Cross, Joseph P. Iddings, Louis Valentine Pirsson, and Henry Stephens Washington in 1912. Cross' group had previously divided the major rock-forming minerals found in igneous rocks into ''salic'' minerals, such as quartz, feldspars, or feldspathoids, and ''femic'' minerals, such as olivine and pyroxene. However, micas and aluminium-rich amphiboles were excluded, while some calcium minerals containing little iron or magnesium, such as wollastonite or apatite, were included ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mountains And Hills Of Snowdonia
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher than a hill, typically rising at least 300 metres (1,000 feet) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges. Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, as well as through erosion by rivers and glaciers. High elevations on mountains produce colder climates than at sea level at similar latitude. These colder climates strongly affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mountains And Hills Of Gwynedd
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher than a hill, typically rising at least 300 metres (1,000 feet) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges. Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, as well as through erosion by rivers and glaciers. High elevations on mountains produce colder climates than at sea level at similar latitude. These colder climates strongly affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dolbenmaen
Dolbenmaen () is a village and community in the Welsh county of Gwynedd, located in Eifionydd, of which it was the administrative centre until 1239. The community includes the villages of Bryncir (), Cenin, Garndolbenmaen, (the largest settlement) Golan, Llanfihangel-y-Pennant, Penmorfa (), Pentrefelin, Wern, Glan-dwyfach, and the hamlet of Prenteg. It has a population of 1,300, increasing slightly to 1,343 at the 2011 Census. The summit of Moel Hebog is shared between Beddgelert and Dolbenmaen. It is a sparsely populated area and covers nearly 100 square kilometres. A castle motte is located to the south of the village which is thought to have been the residence of Llywelyn the Great until the 1230s, when the court moved to a motte and bailey castle at Criccieth. The castle guarded a ford on the Afon Dwyfor which may have been on the Pen Llystyn (Tremadog) to Segontium Roman road. The parish church of St Mary's is a grade II* listed building. South of Pentrefelin is St Cyn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beddgelert
Beddgelert () is a village and community in the Snowdonia area of Gwynedd, Wales. The population of the community taken at the 2011 census was 455, and includes Nantmor and Nant Gwynant. It is reputed to be named after the legendary hound Gelert. The community is large and sparsely populated and covers 86 square kilometres. Location The village stands in a valley at the confluence of the River Glaslyn and the River Colwyn. Just above the confluence of the rivers, in the centre of the village, is an old stone bridge with two arches. The River Gwynant also exists in the area, coinciding with the River Colwyn under what locals know as ‘Pont Bren’, creating the River Glaslyn. Many of the houses and hotels are built of local dark stone. To the west is Moel Hebog and its neighbours to the north and a series of hills rising to the top of Snowdon. A lane of the A4085 between Caernarfon (13 miles north) and Porthmadog (8 miles south) runs through the village. The outdoor e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moel Yr Ogof (view From Moel Hebog)
Moel yr Ogof is a summit in Snowdonia. It is a subsidiary summit of Moel Hebog and a sister peak to the lower Moel Lefn. There is an asbestos trial mine located on the summit. A small seam of white asbestos was discovered however insufficient amounts to commercially mine. Geology The summit of Moel yr Ogof is composed of a brecciated rhyolite, diagnostic of gravitational collapse in a rhyolite dome. Surrounding the crown of the mount is a geological unit consisting of alternating bands, of varying thickness, of pillow basalts and a green/grey sandstone that is of mafic origin, potentially derived from the pillow basalt itself. The pillow basalt is relatively well preserved in places, where devitrification rims clearly outline the individual pillows. It is composed of dark green/black, very fine crystalline, basaltic rock, which has weathered to a dark red/brown colouration due to the presence of iron minerals. The sandstone member of the unit is a pale green/grey, fine to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nantlle Ridge
The Nantlle Ridge ( cy, Crib Nantlle) is the name given to a small range of mountains in Snowdonia, north Wales which runs south-west from the village of Rhyd Ddu for a distance of about , ending above Nebo in the Nantlle Valley. The Nantlle Ridge offers excellent hill walking with fewer crowds than on the more popular parts of Snowdonia. It can be started from either end, but the Rhyd Ddu end tends to be the more popular. There are no great technical difficulties, although a little scrambling may be required on some parts of the ridge. Summits Starting from the Rhyd Ddu end, the Nantlle Ridge is composed of the following peaks (see hill lists in the British Isles for an explanation of the terms "Nuttall", "Hewitt" and "Marilyn"): * Y Garn (); ) — sub-Hewitt, Nuttall * Mynydd Drws-y-Coed (); ) — Hewitt, Nuttall * Trum y Ddysgl (); ) — Marilyn, Hewitt, Nuttall * Mynydd Tal-y-Mignedd (); ) — Hewitt, Nuttall * Craig Cwm Silyn (); ) — Marilyn, Hewitt, Nuttall * Garnedd Goc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea caves, rock shelters, and grottos, that extend a relatively short distance into the rock and they are called ''exogene'' caves. Caves which extend further underground than the opening is wide are called ''endogene'' caves. Speleology is the science of exploration and study of all aspects of caves and the cave environment. Visiting or exploring caves for recreation may be called ''caving'', ''potholing'', or ''spelunking''. Formation types The formation and development of caves is known as ''speleogenesis''; it can occur over the course of millions of years. Caves can range widely in size, and are formed by various geological processes. These may involve a combination of chemical processes, erosion by water, tectonic forces, microorgani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Owain Glyndŵr
Owain ap Gruffydd (), commonly known as Owain Glyndŵr or Glyn Dŵr (, anglicised as Owen Glendower), was a Welsh leader, soldier and military commander who led a 15 year long Welsh War of Independence with the aim of ending English rule in Wales during the Late Middle Ages. He was also an educated lawyer, he formed the first Welsh Parliament ( cy, Senedd Cymru), and was the last native-born Welshman to hold the title Prince of Wales. Owain Glyndŵr was a direct descendant of several Welsh royal dynasties including the princes of Powys via the House of Mathrafal through his father Gruffudd Fychan II, hereditary Prince ( cy, Tywysog) of Powys Fadog. And through his mother, Elen ferch Tomas ap Llywelyn, he was also a descendant of the kings and princes of the Kingdom of Deheubarth as well as the royal House of Dinefwr, and the kings and princes of the Kingdom of Gwynedd and their cadet branch of the House of Aberffraw. The rebellion began in 1400, when Owain Glyndŵr, a descende ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syncline
In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed smaller folds. Synclines are typically a downward fold (synform), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overturned and folded (an antiformal syncline). Characteristics On a geologic map, synclines are recognized as a sequence of rock layers, with the youngest at the fold's center or ''hinge'' and with a reverse sequence of the same rock layers on the opposite side of the hinge. If the fold pattern is circular or elongate, the structure is a basin. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. Notable examples * Powder River Basin, Wyoming, US * Sideling Hill roadcut along Interstate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devitrification
Devitrification is the process of crystallization in a formerly crystal-free (amorphous) glass. The term is derived from the Latin ''vitreus'', meaning '' glassy'' and ''transparent''. Devitrification in glass art Devitrification occurs in glass art during the firing process of fused glass whereby the surface of the glass develops a whitish scum, crazing, or wrinkles instead of a smooth glossy shine, as the molecules in the glass change their structure into that of crystalline solids. While this condition is normally undesired, in glass art it is possible to use devitrification as a deliberate artistic technique. Causes of devitrification, commonly referred to as "devit", can include holding a high temperature for too long, which causes the nucleation of crystals. The presence of foreign residue such as dust on the surface of the glass or inside the kiln prior to firing can provide nucleation points where crystals can propagate easily. The chemical compositions of some types of g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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