Misplaced Pages

#949050

29-1027: Lemhi Pass is a high mountain pass in the Beaverhead Mountains , part of the Bitterroot Range in the Rocky Mountains and within Salmon-Challis National Forest . The pass lies on the Montana - Idaho border on the Continental Divide , at an elevation of 7,373 feet (2,247 m) above sea level . It is accessed via Lemhi Pass Road in Montana, and the Lewis and Clark Highway in Idaho, both gravel roads. Warm Springs Road, which roughly follows

58-449: A critical point at ( 0 , 0 ) {\displaystyle (0,0)} that is a saddle point since it is neither a relative maximum nor relative minimum, but it does not have a relative maximum or relative minimum in the y {\displaystyle y} -direction. The name derives from the fact that the prototypical example in two dimensions is a surface that curves up in one direction, and curves down in

87-409: A different direction, resembling a riding saddle . In terms of contour lines , a saddle point in two dimensions gives rise to a contour map with a pair of lines intersecting at the point. Such intersections are rare in actual ordnance survey maps, as the height of the saddle point is unlikely to coincide with the integer multiples used in such maps. Instead, the saddle point appears as a blank space in

116-531: A nearby mountainside, as with the Eisenhower Tunnel bypassing Loveland Pass in the Rockies, to allow faster traffic flow throughout the year. The top of a pass is frequently the only flat ground in the area, and may be a high vantage point. In some cases this makes it a preferred site for buildings. If a national border follows the ridge of a mountain range, a pass over the mountains is typically on

145-786: A style of street racing which may take place on these roads. There are thousands of named passes around the world, some of which are well-known, such as the Khyber Pass close to the present-day Afghanistan-Pakistan border on the ancient Silk Road , the Great St. Bernard Pass at 2,473 metres (8,114 ft) in the Alps , the Chang La at 5,360 metres (17,590 ft), the Khardung La at 5,359 metres (17,582 ft) in Ladakh , India and

174-506: Is a saddle point is to compute the function's Hessian matrix at that point: if the Hessian is indefinite , then that point is a saddle point. For example, the Hessian matrix of the function z = x 2 − y 2 {\displaystyle z=x^{2}-y^{2}} at the stationary point ( x , y , z ) = ( 0 , 0 , 0 ) {\displaystyle (x,y,z)=(0,0,0)}

203-888: Is also used, particularly in Europe. In the highest mountain range in the world, the Himalayas, passes are denoted by the suffix "La" in Tibetan, Ladhakhi, and several other regional languages. Examples are the Taglang La at 5,328 m (17,480 ft) on the Leh-Manali highway , and the Sia La at 5,589 m (18,337 ft) in the Eastern Karakoram range. Scotland has the Gaelic term bealach (anglicised "balloch"), while Wales has

232-413: Is analogous to the mathematical concept of a saddle surface , with a saddle point marking the minimum high point between two valleys and the lowest point along a ridge. On a topographic map , passes can be identified by contour lines with an hourglass shape, which indicates a low spot between two higher points. In the high mountains, a difference of 2,000 meters (6,600 ft) between the summit and

261-514: Is both a stationary point and a point of inflection . Since it is a point of inflection, it is not a local extremum . A saddle surface is a smooth surface containing one or more saddle points. Classical examples of two-dimensional saddle surfaces in the Euclidean space are second order surfaces, the hyperbolic paraboloid z = x 2 − y 2 {\displaystyle z=x^{2}-y^{2}} (which

290-461: Is found to be enriched in the middle rare earths, specifically neodymium (Nd), as there is estimated to be 35 weight percent of Nd in the monazite. Neodymium, cerium , gadolinium , yttrium , and dysprosium are the top lanthanide minerals recorded to be attainable in the Lemhi Pass. Mountain pass Mountain passes make use of a gap , saddle , col or notch . A topographic saddle

319-399: Is often referred to as " the saddle surface" or "the standard saddle surface") and the hyperboloid of one sheet . The Pringles potato chip or crisp is an everyday example of a hyperbolic paraboloid shape. Saddle surfaces have negative Gaussian curvature which distinguish them from convex/elliptical surfaces which have positive Gaussian curvature. A classical third-order saddle surface is

SECTION 10

#1732772163950

348-771: Is the Brenner pass in the Alps . Some mountain passes above the tree line have problems with snow drift in the winter. This might be alleviated by building the road a few meters above the ground, which will make snow blow off the road. There are many words for pass in the English-speaking world. In the United States, pass is very common in the West , the word gap is common in the southern Appalachians , notch in parts of New England , and saddle in northern Idaho . The term col , derived from Old French,

377-428: Is the matrix which is indefinite. Therefore, this point is a saddle point. This criterion gives only a sufficient condition. For example, the point ( 0 , 0 , 0 ) {\displaystyle (0,0,0)} is a saddle point for the function z = x 4 − y 4 , {\displaystyle z=x^{4}-y^{4},} but the Hessian matrix of this function at

406-463: The Lagrangian . In dynamical systems , if the dynamic is given by a differentiable map f then a point is hyperbolic if and only if the differential of ƒ (where n is the period of the point) has no eigenvalue on the (complex) unit circle when computed at the point. Then a saddle point is a hyperbolic periodic point whose stable and unstable manifolds have a dimension that

435-695: The Lewis and Clark Expedition crossed the Continental Divide at Lemhi Pass. Lewis found a "large and plain Indian road" over the pass. This was the first time that white men had seen present-day Idaho: We proceeded to the top of the dividing ridge from which I discovered immense ranges of high mountains still to the West of us with their tops partially covered in snow The next day Lewis met Cameahwait and his band of Shoshone, and returned with them across

464-594: The Palakkad Gap at 140 metres (460 ft) in Palakkad , Kerala , India . The roads at Mana Pass at 5,610 metres (18,410 ft) and Marsimik La at 5,582 metres (18,314 ft), on and near the China–India border respectively, appear to be world's two highest motorable passes. Khunjerab Pass between Pakistan and China at 4,693 metres (15,397 ft) is also a high-altitude motorable mountain pass. One of

493-405: The monkey saddle . In a two-player zero sum game defined on a continuous space, the equilibrium point is a saddle point. For a second-order linear autonomous system, a critical point is a saddle point if the characteristic equation has one positive and one negative real eigenvalue . In optimization subject to equality constraints, the first-order conditions describe a saddle point of

522-458: The border, and there may be a border control or customs station, and possibly a military post. For instance, Argentina and Chile share the world's third-longest international border , 5,300 kilometres (3,300 mi) long, which runs north–south along the Andes mountains and includes 42 mountain passes. On a road over a pass, it is customary to have a small roadside sign giving the name of

551-633: The divide in Montana, passes just west of the pass's high point. The pass gained importance in the 18th century, when the Lemhi Shoshone acquired horses and used the route to travel between the two main parts of their homeland. From the time of the Louisiana Purchase in 1803 until the Oregon Treaty in 1846 the pass marked the western border of the United States. On August 12, 1805 Meriwether Lewis and three other members of

580-486: The famous but non-motorable mountain passes is Thorong La at 5,416 metres (17,769 ft) in Annapurna Conservation Area , Nepal. Saddle point In mathematics , a saddle point or minimax point is a point on the surface of the graph of a function where the slopes (derivatives) in orthogonal directions are all zero (a critical point ), but which is not a local extremum of

609-611: The first non-Indians to establish a sustained relationship with the Salmon River Indian people. During the mining era the pass was used by stagecoaches, but the route fell into disuse after 1910, when the Gilmore and Pittsburgh Railroad was built through the nearby Bannock Pass . Only a single track dirt road now crosses the pass. The pass was designated a National Historic Landmark in 1960. The Lemhi Pass district has been found to host many lanthanide minerals and

SECTION 20

#1732772163950

638-415: The function. An example of a saddle point is when there is a critical point with a relative minimum along one axial direction (between peaks) and at a relative maximum along the crossing axis. However, a saddle point need not be in this form. For example, the function f ( x , y ) = x 2 + y 3 {\displaystyle f(x,y)=x^{2}+y^{3}} has

667-420: The middle of four sets of contour lines that approach and veer away from it. For a basic saddle point, these sets occur in pairs, with an opposing high pair and an opposing low pair positioned in orthogonal directions. The critical contour lines generally do not have to intersect orthogonally. A simple criterion for checking if a given stationary point of a real-valued function F ( x , y ) of two real variables

696-434: The mountain is defined as a mountain pass. Passes are often found just above the source of a river , constituting a drainage divide . A pass may be very short, consisting of steep slopes to the top of the pass, or a valley many kilometers long, whose highest point might only be identifiable by surveying . Roads and railways have long been built through passes. Some high and rugged passes may have tunnels bored underneath

725-408: The origin is the null matrix , which is not indefinite. In the most general terms, a saddle point for a smooth function (whose graph is a curve , surface or hypersurface ) is a stationary point such that the curve/surface/etc. in the neighborhood of that point is not entirely on any side of the tangent space at that point. In a domain of one dimension, a saddle point is a point which

754-479: The pass and its elevation above mean sea level . Apart from offering relatively easy travel between valleys, passes also provide a route between two mountain tops with a minimum of descent. As a result, it is common for tracks to meet at a pass; this often makes them convenient routes even when travelling between a summit and the valley floor. Passes traditionally were places for trade routes, communications, cultural exchange, military expeditions etc. A typical example

783-554: The pass to meet Clark. On August 26, 1805 the entire expedition crossed the pass. In the early 19th century the pass was regularly used by the Blackfoot people, so that in 1824 Alexander Ross referred to the route as the Blackfoot route. At that time the pass itself was known as North Pass, to distinguish it from South Pass . The pass derives its present name from Fort Lemhi , founded in 1855 by Mormon missionaries who were

812-659: The richest deposit of thorium in the US. In a study of 31 samples taken from 21 different veins, the ratio of rare-earth elements (REEs) in the area is estimated to be between 0.05-9.2%. This depends largely on the localized mineralogy and REE mineralization. Most commonly the thorium is found as thorite hosted in quartz veins, whereas REEs are contained within monazite . The deposits lie within quartz veins hosted in Precambrian rock with minerals such as hematite , apatite , feldspar , thorite and monazite present. The monazite

841-696: The similar bwlch (both being insular Celtic languages). In the Lake District of north-west England, the term hause is often used, although the term pass is also common—one distinction is that a pass can refer to a route, as well as the highest part thereof, while a hause is simply that highest part, often flattened somewhat into a high-level plateau. In Japan they are known as tōge , which means "pass" in Japanese. The word can also refer to narrow, winding roads that can be found in and around mountains and geographically similar areas, or specifically to

#949050