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22-587: A plain of alluvial deposits , Méma is situated north of Massina , west of Lake Debo and the Inner Niger Delta , and southwest of the Lakes Region. The now-senescent basin may have been the first settlement area for communities who migrated from distressed homelands of the Sahara during the last two millennia BC. Méma was inhabited by 3800 BCE at the earliest by migrants from Azawad fleeing

44-403: A gap , saddle , col or notch . A topographic saddle 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,

66-455: A pass (sometimes termed a gap ). Coastal plains mostly rise from sea level until they run into elevated features such as mountains or plateaus. Plains can be formed from flowing lava ; from deposition of sediment by water, ice, or wind; or formed by erosion by the agents from hills or mountains. Biomes on plains include grassland ( temperate or subtropical ), steppe ( semi-arid ), savannah ( tropical ) or tundra ( polar ). In

88-502: A difference of 2,000 meters (6,600 ft) between the summit and 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

110-538: A few instances, deserts and rainforests may also be considered plains. Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile , and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock . The types of depositional plains include: Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out

132-531: 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

154-786: 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

176-888: 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

198-771: 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,

220-686: The Mali Empire , within which Mema held a special, more autonomous status. In 1433 the kingdom regained its independence before falling to the Songhai Empire by the middle of the century. Toladié, which dates between at least 430 CE and 670 CE, is the largest occupation site (76 hectares) in Mema. As a primary center in the region, Toladié utilized smelted iron tools produced by the communities of Akumbu, Boubou, Boundou, Boulel, Kobadie, Kolima, and Nampala for purposes of tribute and trade with

242-594: 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

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264-541: The Earth's surface. Mountain pass Aa mountain pass is a navigable route through a mountain range or over a ridge . Since mountain ranges can present formidable barriers to travel, passes have played a key role in trade, war, and both human and animal migration throughout history. At lower elevations it may be called a hill pass . A mountain pass is typically formed between two volcanic peaks or created by erosion from water or wind. Mountain passes make use of

286-517: The Ghana Empire. At the Akumbu mound complex, in Mema, its archaeological findings date between 400 CE and 1400 CE; at the cultural deposit of AK3, which contained three human remains, the dates range between 400 CE and 600 CE. While two out of three human remains were in a fully decomposed state, one of the human remains were able to be determined to be a young adult (17–25 years old) female, who

308-472: The base of mountains , as coastal plains , and as plateaus or uplands . Plains are one of the major landforms on earth, where they are present on all continents, and cover more than one-third of the world's land area. In a valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs . Where a geological region contains more than one plain, they may be connected by

330-458: 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

352-608: The drying Sahara. It was host to a large number of Stone Age villages, succeeded by hundreds of Iron Age cities, far pre-dating the settlement of Djenne-Jeno . Historically, Méma was one of the smaller Soninke states, an important vassal or province of the Wagadou Empire . According to local legends it was founded by Biranin Tounkara, a slave or companion of Dinga , the legendary founder of Wagadou. Historian Dierk Lange has argued that Ghana, rather than being situated to

374-429: The major landforms on earth, being present on all continents and covering more than one-third of the world's land area. Plains in many areas are important for agriculture . There are various types of plains and biomes on them. A plain or flatland is a flat expanse of land with a layer of grass that generally does not change much in elevation , and is primarily treeless. Plains occur as lowlands along valleys or at

396-621: The northwest of the Niger Delta, was in fact centered in the Méma area. After Wagadou's collapse around the end of the 12th century, Méma was one of the most important Soninke successor states. It appears several times in the Epic of Sundiata . The Tunkara (king) of Mema shelters Sundiata when he flees the Manding region , then provides cavalry to help him overthrow Soumaoro Kante and establish

418-479: 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

440-400: The rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains . Structural plains are relatively undisturbed horizontal surfaces of the Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on

462-696: 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

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484-492: Was buried with two copper bracelets - one on each wrist, 13 cowrie shells , 11 stone beads, and a fully intact pot. Plain In geography , a plain , commonly known as flatland , is a flat expanse of land that generally does not change much in elevation , and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains , as coastal plains , and as plateaus or uplands . Plains are one of

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