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Lairg Gravity Low
The Lairg gravity low is a possible impact crater in Scotland about 40 kilometres in diameter, with a centre near the town of Lairg in the Scottish Highlands. Its identity as an impact crater is suspected due to the impact deposits present in the Stac Fada Member 50 km to the west. However, this has been disputed, with other studies suggesting that an impact in The Minch is more likely. Description Relative to the residual gravity field, at the centre it is 23 mGal lower than the surrounding terrain. The gravity anomaly is approximately 40 km across, and somewhat irregularly shaped towards the edges. It is quite similar to that of the Ries impact crater. A detailed analysis of the gravity data found that the anomaly has no central uplift as would be expected of a crater of this size, though it possessed anomalies that was suggested represented a peak ring. The authors proposed that the anomaly was an eroded remnant of a larger (~ 100 km diameter) crater, which w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lairg
Lairg ( gd, An Luirg, meaning "the shank/shin") is a village and parish in Sutherland, Scotland. It has a population of 891 and is at the south-eastern end of Loch Shin. Lairg is unusual in the northern Highlands in being a large settlement that is not on the coast. One of the reasons that Lairg is slightly bigger than other non-coastal Highland villages is its central location within the county of Sutherland. Having four roads which meet in the village, it used to be known as "The Crossroads of the North". In the 19th century, it was provided with a railway station (at ), on what is now the Far North Line. This development means that the north-west of Sutherland is now easier to reach. (The Far North Line links Inverness in the south with Thurso and Wick in the north.) Sheep sales Lairg is the location of the largest single-day sheep sale in Europe. These auctions take place in August and bring people from all over Scotland to buy or sell their animals. Gala Week In July, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Anomaly
The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity measured at every point on its surface would be given precisely by a simple algebraic expression. However, the Earth has a rugged surface and non-uniform composition, which distorts its gravitational field. The theoretical value of gravity can be corrected for altitude and the effects of nearby terrain, but it usually still differs slightly from the measured value. This gravity anomaly can reveal the presence of subsurface structures of unusual density. For example, a mass of dense ore below the surface will give a positive anomaly due to the increased gravitational attraction of the ore. Different theoretical models will predict different values of gravity, and so a gravity anomaly is always specified with reference to a particular model. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stoer Group
In geology, the term Torridonian is the informal name for the Torridonian Group, a series of Mesoproterozoic to Neoproterozoic arenaceous and argillaceous sedimentary rocks, which occur extensively in the Northwest Highlands of Scotland. The strata of the Torridonian Group are particularly well exposed in the district of upper Loch Torridon, a circumstance which suggested the name Torridon Sandstone, first applied to these rocks by James Nicol. Stratigraphically, they lie unconformably on gneisses of the Lewisian complex and their outcrop extent is restricted to the Hebridean Terrane. Rock type The rocks are mainly red and brown sandstones, arkoses and shales with coarse conglomerates locally at the base. Some of the materials of these rocks were derived from the underlying Lewisian gneiss, upon the uneven surface of which they rest, but the bulk of the material was obtained from rocks that are nowhere now exposed. Upon this ancient denuded land surface the Torridonian strata ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithic Fragment (geology)
Lithic fragments, or lithics, are pieces of other rocks that have been eroded down to sand size and now are sand grains in a sedimentary rock. They were first described and named (in their modern definitions) by Bill Dickinson in 1970. Lithic fragments can be derived from sedimentary, igneous or metamorphic rocks. A lithic fragment is defined using the Gazzi-Dickinson point-counting method and being in the sand-size fraction. Sand grains in sedimentary rocks that are fragments of larger rocks that are not identified using the Gazzi-Dickinson method are usually called rock fragments instead of lithic fragments. Sandstones rich in lithic fragments are called lithic sandstones.Lithic fragments can also be define as the breakdown of preexisting ,fine -to medium grained igneous . metamorphic and sedimentary rocks results in sand -sized fragments.. Types Igneous (Lv) These can include granular (~rhyolitic), microlitic (~andesitic), lathwork (~basaltic), and vitric ( glassy). These ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct cleavage. In other words, it is a metamorphic rock composed of mineral grains easily seen with the unaided eye, which form obvious compositional layers, but which has only a weak tendency to fracture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palaeocurrent
A paleocurrent or paleocurrent indicator is a geological feature (typically a sedimentary structure) that helps one determine the direction of flowing water in the geologic past. This is an invaluable tool in the reconstruction of ancient depositional environments. There are two main types of paleocurrent indicators: *''Unidirectional'', which give a clear, single direction of flow *''Bidirectional'', which give a good linear direction, but it is unclear which direction along the linear trend the water flowed. Paleocurrents are usually measured with an azimuth, or as a rake on a bedding plane, and displayed with a Rose Diagram to show the dominant direction(s) of flow. This is needed because in some depositional environments, like meandering rivers, the paleocurrent resulting from natural sinuosity has a natural variation of 180 degrees or more. Below are a partial list of common paleocurrent indicators: Unidirectional *Cross-bedding – the axis of a trough cross bed or the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peak Ring (crater)
A peak ring crater is a type of complex crater, which is different from a multi-ringed basin or central-peak crater. A central peak is not seen; instead, a roughly circular ring or plateau, possibly discontinuous, surrounds the crater's center, with the crater rim still farther out from the center. Formation The rings form by different processes, and inner rings may not be formed by the same processes as outer rings.Geology Pagewww.geologypage.com/2016/10/research-helps-explain-formation-ringed-crater-moon.html accessdate: February 5, 2017 It has long been the view that peak rings are formed in the stage subsequent to central peak formation in craters. The central peaks of craters are believed to originate from hydrodynamic flow of material lifted by inward-collapsing crater walls, while impact-shattered rock debris is briefly turned to fluid by strong vibrations that develop during crater formation. The peak-ring structure of Chicxulub crater was probably formed as inward-colla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nördlinger Ries
The Nördlinger Ries is an impact crater and large circular depression in western Bavaria and eastern Baden-Württemberg. It is located north of the Danube in the district of Donau-Ries. The city of Nördlingen is located within the depression, about south-west of its centre. Etymology "Ries" is derived from Raetia, since the tribe of Raetians lived in the area in pre-Roman times. Description The depression is a meteorite impact crater formed 14.808 ± 0.038 million years ago in the Miocene. The crater is most commonly referred to simply as ''Ries crater'' or ''the Ries''. The original crater rim had an estimated diameter of . The present floor of the depression is about below the eroded remains of the rim. It was originally assumed that the Ries was of volcanic origin. In 1960 Eugene Shoemaker and Edward C. T. Chao showed that the depression was caused by meteorite impact. The key evidence was the presence of coesite, which, in unmetamorphosed rocks, can only be fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gal (unit)
The gal (symbol: Gal), sometimes called galileo after Galileo Galilei, is a unit of acceleration sometimes used in gravimetry. BIPM ''SI brochure'', 8th ed. 2006Table 9: Non-SI units associated with the CGS and the CGS-Gaussian system of units. The gal is defined as 1 centimeter per second squared (1 cm/s2). The milligal (mGal) and microgal (µGal) are respectively one thousandth and one millionth of a gal. The gal is not part of the International System of Units (known by its French-language initials "SI"). In 1978 the CIPM decided that it was permissible to use the gal "with the SI until the CIPM considers that tsuse is no longer necessary". However, use of the gal is deprecated by ISO 80000-3:2006. The gal is a derived unit, defined in terms of the centimeter–gram–second (CGS) base unit of length, the centimeter, and the second, which is the base unit of time in both the CGS and the modern SI system. In SI base units, 1 Gal is equal to 0.01 m/s2. The a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the north and west, the North Sea to the northeast and east, and the Irish Sea to the south. It also contains more than 790 islands, principally in the archipelagos of the Hebrides and the Northern Isles. Most of the population, including the capital Edinburgh, is concentrated in the Central Belt—the plain between the Scottish Highlands and the Southern Uplands—in the Scottish Lowlands. Scotland is divided into 32 administrative subdivisions or local authorities, known as council areas. Glasgow City is the largest council area in terms of population, with Highland being the largest in terms of area. Limited self-governing power, covering matters such as education, social services and roads and transportation, is devolved from the Scott ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Minch
The Minch ( gd, An Cuan Sgitheanach, ', ', '), also called North Minch, is a strait in north-west Scotland, separating the north-west Scottish Highlands, Highlands and the northern Inner Hebrides from Lewis and Harris in the Outer Hebrides. It was known as ("Scotland's fjord/firth") in Old Norse. The Lower Minch (), also known as the Little Minch, is the Minch's southern extension, separating Skye from the lower Outer Hebrides: North Uist, Benbecula, South Uist, Barra etc. It opens into the Sea of the Hebrides. The Little Minch is the northern limit of the Sea of the Hebrides. Geography The Minch and Lower Minch form part of the Inner Seas off the West Coast of Scotland, as defined by the International Hydrographic Organization. The Minch ranges from wide and is approximately long. It is believed to be the site of the Ullapool bolide impact, biggest meteorite ever to hit the British Isles. The Lower Minch is about wide. In June 2010 Eilidh Macdonald became the first person ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stac Fada Member
The Stac Fada Member is a distinctive layer towards the top of the Mesoproterozoic Bay of Stoer Formation, part of the Stoer Group (lowermost Torridonian Supergroup) in northwest Scotland. This rock unit is generally thick and is made of sandstone that contains accretionary lapilli and many dark green glassy fragments of mafic composition. Evidence for a meteorite impact in the area of the Minch or near Lairg has been published and refined in a series of studies from 2008 to 2019. The unit dates to approximately 1.2 billion years ago. The name comes from a small promontory to the west of the village of Stoer, in Assynt, Sutherland (at ). Extent The Stac Fada Member is exposed at a series of localities on or near the coast of Wester Ross, extending for about from the western side of Loch Ewe in the south to the Stoer peninsula in the north. Description The Stac Fada Member is an impactite consisting of a mixture of suevite and clast poor impact melt rocks. At the Stoer penins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
