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44-779: The Morar Group outcrops over a large part of the Northwest Highlands , between the Moine Thrust Belt to the northwest to the contact with the Glennfinnan Group, marked by the Sgurr Beag Thrust or Swordly Thrust, or locally Devonian rocks in southeast Sutherland, to the southeast. It reaches the north coast of Sutherland to the north and extends as far south as the Ross of Mull . The group has been subdivided in several parts of its outcrop. In

88-480: A Rock = % Δ A = A f − A i A i × 100 {\displaystyle \%\Delta A={\frac {A_{f}-A_{i}}{A_{i}}}\times 100} Where: A i {\displaystyle A_{i}} = Initial Area A f {\displaystyle A_{f}} = Final Area For each of these methods of quantifying, one must take measurements of both

132-430: A change in rock failure mode, at an approximate average depth of 10–15 km (~ 6.2–9.3 miles) in continental crust , below which rock becomes less likely to fracture and more likely to deform ductilely. The zone exists because as depth increases confining pressure increases, and brittle strength increases with confining pressure whilst ductile strength decreases with increasing temperature. The transition zone occurs at

176-403: A linear stress vs strain relationship past the elastic limit. Ductile deformation is typically characterized by diffuse deformation (i.e. lacking a discrete fault plane ) and on a stress-strain plot is accompanied by steady state sliding at failure, compared to the sharp stress drop observed in experiments during brittle failure . The brittle–ductile transition zone is characterized by

220-630: A very low population density. Significant settlements are Kyle of Lochalsh , Mallaig , Dingwall , Dornoch , and Ullapool . The city of Inverness , known as the "Capital of the Highlands", on the eastern margin of the Northwest Highlands, is by far the largest settlement in the region and is the administrative centre for the Highland Council area . Ductility (Earth science) In Earth science , ductility refers to

264-486: Is a material property that can be expressed in a variety of ways. Mathematically, it is commonly expressed as a total quantity of elongation or a total quantity of the change in cross sectional area of a specific rock until macroscopic brittle behavior, such as fracturing, is observed. For accurate measurement, this must be done under several controlled conditions, including but not limited to Pressure , Temperature , Moisture Content , Sample Size, etc., for all can impact

308-557: Is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward. At low elevations and near the coast the climate is maritime. The summers are mild and wet with average daytime highs under 17 °C, or 62.6 °F. The winters are cool at low elevation with average night-time lows below 0 °C, or 32 °F, but become colder and snowier inland and at higher elevations with

352-711: Is deformation which exhibits a linear stress-strain relationship (quantified by Young's Modulus) and is derived from Hooke's Law of spring forces (see Fig. 1.2). In elastic deformation, objects show no permanent deformation after the stress has been removed from the system and return to their original state. σ = E ϵ {\displaystyle \sigma =E\epsilon } Where: σ {\displaystyle \sigma } = Stress (In Pascals) E {\displaystyle E} = Young's Modulus (In Pascals) ϵ {\displaystyle \epsilon } = Strain (Unitless) Viscous Deformation Viscous Deformation

396-928: Is divided into the lower Altnaharra Psammite Formation, with the Glen Achall Semipelite Member at the top, and the upper Glascarnoch Psammite Formation. The Vaich Pelite Formation is the equivalent of the Morar Schists and the Crom Psammite Formation is matched to the Upper Psammite. Above this is the Diebidale Pelite Formation. On the Ross of Mull, four formations are recognised: the Lower Shiaba Psammite Formation at

440-506: Is governed by both the external conditions around the rock and the internal conditions sample. External conditions include temperature, confining pressure, presence of fluids, etc. while internal conditions include the arrangement of the crystal lattice, the chemical composition of the rock sample, the grain size of the material, etc. Ductilely Deformative behavior can be grouped into three categories: Elastic, Viscous, and Crystal-Plastic Deformation. Elastic Deformation Elastic Deformation

484-598: Is separated from the Grampian Mountains by the Great Glen (Glen More). The region comprises Wester Ross , Assynt , Sutherland and part of Caithness . The Caledonian Canal , which extends from Loch Linnhe in the south-west, via Loch Ness to the Moray Firth in the north-east splits this area from the rest of the country. The city of Inverness and the town of Fort William serve as gateways to

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528-636: Is the summit of Càrn Eige at an elevation of 1,183 metres (3,881 feet) above sea level. By comparison, across the Great Glen to the south, the Grampians includes Ben Nevis which is highest point in the British Isles at 1,345 metres. The aurora borealis is sometimes visible on winter nights, especially at the climax of the 11-year cycle. Bordering the region to the northeast is the lowland area of Caithness . There are relatively few roads, and many are single lane (with passing places). The region has

572-890: Is when rocks behave and deform more like a fluid than a solid. This often occurs under great amounts of pressure and at very high temperatures. In viscous deformation, stress is proportional to the strain rate, and each rock sample has its own material property called its Viscosity . Unlike elastic deformation, viscous deformation is permanent even after the stress has been removed. σ = η ξ {\displaystyle \sigma =\eta \xi } Where: σ {\displaystyle \sigma } = Stress (In Pascals) η {\displaystyle \eta } = Viscosity (In Pascals * Seconds) ξ {\displaystyle \xi } = Strain Rate (In 1/Seconds) Crystal-Plastic Deformation Crystal-Plastic Deformation occurs at

616-555: The Cambrian and Ordovician rocks of the northwest margin along the Moine Thrust Belt . The geological understanding of thrust faulting slowly developed in the 19th century in what became known as the " Highlands Controversy ". . Considering its high northerly latitude of about 57 to 58 degrees north and the mountainous terrain, the climate is mild, moderated by the warming influence of the North Atlantic Drift which

660-535: The Grenville Orogen and the Morar Group more distal. Previous models of a rift setting are not consistent with the scale of the sedimentary systems observed, nor are there the expected rapid vertical and lateral changes in sedimentary facies typical of rift basins. The oldest age of the Morar Group is constrained by the results of detrital zircon geochronology while the youngest age is constrained by

704-650: The Knoydart and Morar areas, a fourfold subdivision is recognised starting from the oldest: Basal Pelite Formation, Lower Morar Psammite Formation, Morar Schists Formation and Upper Morar Psammite Formation. Further north in Ross-shire , extending into Sutherland, the Basal Pelite and the lower part of the Lower Psammite is interpreted to be missing but the sequence is otherwise similar. The Lower Psammite

748-534: The Knoydartian are estimated at about 7 kb and 650°C. The D1 structures in the Glenelg area are affected by two later phases of folding that have been assigned to late Grampian (D2 460–440 Ma) and Scandian (D3). Northwest Highlands 57°30′N 5°0′W  /  57.500°N 5.000°W  / 57.500; -5.000 The Northwest Highlands are located in the northern third of Scotland that

792-896: The Loch Ness Supergroup. In Sutherland the Morar Group are affected by a series of ductile thrust faults that carry slices of the Altnaharra Psammite, each with a piece of Lewisian-type basement just above the thrust. Between the Moine Thrust and the Swordly Thrust (which is interpreted to form the base to the Glenfinnan Group in this part of the outcrop), there are the Ben Hope Thrust, the Dherue/Achness Thrust,

836-656: The Meadie Schist is 950–940 Ma at pressure /temperature conditions of 6–7 kb and 600°C. There is much more evidence of Knoydartian orogenesis across the Morar Group outcrop and it seems to have produced major structures. Around the Glenelg inlier , which is formed of Lewisian type gneisses and eclogites of Grenvillian age, the first stage of deformation (D1) within the Morar Group is interpreted to be Knoydartian age south-southeast directed ductile thrusting and related isoclinal folding . The peak metamorphic conditions for

880-844: The Naver Thrust and the Torrisdale Thrust. At least four orogenic events have been interpreted to affect the Morar Group, in order of age, the Renlandian, the Knoydartian , and the Grampian and Scandian phases of the Caledonian Orogeny . The effects of the Relandian Orogeny have only been recognised locally within the group in northern Sutherland. The age range calculated for garnets sampled in

924-606: The Torridon Group with which they have been correlated within the Wester Ross Supergroup. Due to movement on the Moine Thrust, the depositional areas of the Torridon and Morar groups are likely to have been separated by more than 100 km. These similarities are consistent with a model in which both sequences were deposited in a foreland basin , with the Torridon Group being more proximal to the mountains of

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968-492: The atomic scale and is governed by its own set of specific mechanisms that deform crystals by the movements of atoms and atomic planes through the crystal lattice. Like viscous deformation, it is also a permanent form of deformation. Mechanisms of crystal-plastic deformation include Pressure solution , Dislocation creep , and Diffusion creep . In addition to rocks, biological materials such as wood, lumber, bone, etc. can be assessed for their ductility as well, for many behave in

1012-731: The base (no older beds exposed), the Shiaba Pelite Formation, the Upper Shiaba Psammite Formation and the Laggan Mor Formation, which becomes increasingly highly deformed as it approaches its contact with the younger Glennfinnan Group. In the lower strain areas there are sufficient sedimentary structures preserved to provide constraints on the depositional environment for the Morar Group. The main challenge has been differentiating between shallow marine shelf and fluvial settings for

1056-411: The capacity of a rock to deform to large strains without macroscopic fracturing. Such behavior may occur in unlithified or poorly lithified sediments , in weak materials such as halite or at greater depths in all rock types where higher temperatures promote crystal plasticity and higher confining pressures suppress brittle fracture. In addition, when a material is behaving ductilely, it exhibits

1100-603: The coast or at low elevations but may lie for up to 105 days per year, persisting into the summer months, at the highest elevations. Naturally, the area would be a vast birch, pine and montane shrub forest, such as those surviving in Glen Affric . The region has steep, glacier-carved mountains, glens and interspersed plains. Many islands (which also vary widely in geography) lie off the coast. Elevations of around 750 metres (2,500 feet) or over are common, as are mountains exceeding 3,000 feet or 914 m ( Munros ). The highest point

1144-528: The dating of the oldest metamorphic/tectonic event that has affected the group since deposition. The youngest detrital zircon and rutile ages found for samples from the Morar Group are 1070–1000 Ma (million years ago). The oldest metamorphic event known from the Morar Group is that associated with the Renlandian Orogeny , which gives ages of 950–940 Ma, using Lu-Hf and Sm–Nd methods. Together these give an age range of 1000–950 Ma for deposition of

1188-532: The deposition of the Vaich Pelite Formation. This is interpreted to be a single progradation-retrogradation cycle. A second cycle began with a return to shallow water deposition in the lower part of the Crom Psammite Formation, grading upwards to a distal braid plain setting, before returning to a tidal shoreline and eventually to shallow water marine deposition in the Diebidale Pelite Formation. A very similar pattern of cycles have been deduced for

1232-491: The deposition of the sequence. For the Ross succession, the Basal Pelite is interpreted to represent deposition in paleovalleys, similar to the Diabaig Formation of the Torridon Group. The Altnaharra Psammite is interpreted to have been deposited as a prograding braid plain , with fluvial deposition being replaced by shoreline deposits that were tidally influenced, before a deeper marine environment developed during

1276-406: The dominant deformation process. Gouge and Breccia form in the uppermost, brittle regime while Cataclasite and Pseudotachylite form in the lower parts of the brittle regime, edging upon the transition zone. Mylonite forms in the more ductile regime at greater depths while Blastomylonite forms well past the transition zone and well into the ductile regime, even deeper into the crust. Ductility

1320-543: The ductility and material properties of a biological substance. Peak Ductility Demand is a quantity used particularly in the fields of architecture, geological engineering, and mechanical engineering. It is defined as the amount of ductile deformation a material must be able to withstand (when exposed to a stress) without brittle fracture or failure. This quantity is particularly useful in the analysis of failure of structures in response to earthquakes and seismic waves. It has been shown that earthquake aftershocks can increase

1364-416: The group. The structure of the Morar Group varies from south to north. In the southern part of the outcrop, around areas such as Morar, Knoydart and Loch Monar , rocks of this group are often intensely deformed. Loch Monar was the area where John G. Ramsay unravelled the complex history of multiple phases of deformation. The folding involves the Sgurr Beag Thrust, showing that it postdates the deposition of

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1408-495: The highest tops exhibiting a tundra climate. The Northwest Highlands are, on average, not as cold as the higher, snowier Cairngorm mountains which lie to the southeast. However, on 30 December 1995, the UK's lowest temperature was recorded at Altnaharra, at −27.2 °C (−17.0 °F). This matched a similar recording at Braemar in the Grampians on 11 February 1895 and on 10 January 1982. Snow does not usually lie for significant periods at

1452-410: The initial and final dimensions of the rock sample. For Elongation, the measurement is a uni-dimensional initial and final length, the former measured before any Stress is applied and the latter measuring the length of the sample after fracture occurs. For Area, it is strongly preferable to use a rock that has been cut into a cylindrical shape before stress application so that the cross-sectional area of

1496-411: The lumber, lack of defects such as knots or grain distortions, temperature at 20 C, relative humidity at 65%, and size of the cut shapes of the wood samples. Results obtained from the experiment exhibited a linear stress-strain relationship during elastic deformation but also an unexpected non-linear relationship between stress and strain for the lumber after the elastic limit was reached, deviating from

1540-824: The measured ductility. It is important to understand that even the same type of rock or mineral may exhibit different behavior and degrees of ductility due to internal heterogeneities small scale differences between each individual sample. The two quantities are expressed in the form of a ratio or a percent. % Elongation of a Rock = % Δ l = l f − l i l i × 100 {\displaystyle \%\Delta l={\frac {l_{f}-l_{i}}{l_{i}}}\times 100} Where: l i {\displaystyle l_{i}} = Initial Length of Rock l f {\displaystyle l_{f}} = Final Length of Rock % Change in Area of

1584-490: The model of plasticity theory. Multiple reasons were suggested as to why this came about. First, since wood is a biological material, it was suggested that under great stress in the experiment, the crushing of cells within the sample could have been a cause for deviation from perfectly plastic behavior. With greater destruction of cellular material, the stress-strain relationship is hypothesized to become more and more nonlinear and non-ideal with greater stress. Additionally, because

1628-452: The peaks, such as Beinn Eighe and Canisp , are topped with later light grey or white Cambrian quartzite . Cambro- Ordovician limestone is also to be found in a narrow outcrop between Durness and Skye . The larger part of the region is formed from rocks of the Moine succession much of which is metamorphosed sandstones ( psammites ) and schist . These have over-ridden the gneiss and

1672-459: The point where brittle strength equals ductile strength. In glacial ice this zone is at approximately 30 m (100 ft) depth. Not all materials, however, abide by this transition. It is possible and not rare for material above the transition zone to deform ductilely, and for material below to deform in a brittle manner. The depth of the material does exert an influence on the mode of deformation, but other substances, such as loose soils in

1716-460: The region from the south. The geology of the Highlands is complex. Along the western coastal margin it is characterised by Lewisian gneiss , the oldest rock in Scotland. Liathach , Beinn Alligin , Suilven , Cùl Mòr , Cùl Beag , and Quinag are just some of the impressive rock islands of the significantly younger rich brown-coloured Torridonian sandstone which rests on the gneiss. Some of

1760-736: The same manner and possess the same characteristics as abiotic Earth materials. This assessment was done in Hiroshi Yoshihara's experiment, "Plasticity Analysis of the Strain in the Tangential Direction of Solid Wood Subjected to Compression Load in the Longitudinal Direction." The study aimed to analyze the behavioral rheology of 2 wood specimens, the Sitka Spruce and Japanese Birch. In the past, it

1804-400: The sample can be taken. Cross-Sectional Area of a Cylinder = Area of a Circle = A = π r 2 {\displaystyle A=\pi r^{2}} Using this, the initial and final areas of the sample can be used to quantify the % change in the area of the rock. Any material is shown to be able to deform ductilely or brittlely, in which the type of deformation

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1848-570: The samples were inhomogeneous (non-uniform) materials, it was assumed that some bending or distortion may have occurred in the samples that could have deviated the stress from being perfectly uniaxial. This may have also been induced by other factors like irregularities in the cellular density profile and distorted sample cutting. The conclusions of the research accurately showed that although biological materials can behave like rocks undergoing deformation, there are many other factors and variables that must be considered, making it difficult to standardize

1892-458: The upper crust, malleable rocks, biological debris, and more are just a few examples of that which does not deform in accordance to the transition zone. The type of dominating deformation process also has a great impact on the types of rocks and structures found at certain depths within the Earth's crust. As evident from Fig. 1.1, different geological formations and rocks are found in accordance to

1936-457: Was shown that solid wood, when subjected to compressional stresses, initially has a linear stress-strain diagram (indicative of elastic deformation) and later, under greater load, demonstrates a non-linear diagram indicative of ductile objects. To analyze the rheology, the stress was restricted to uniaxial compression in the longitudinal direction and the post-linear behavior was analyzed using plasticity theory. Controls included moisture content in

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