ALLUVIUM, soil or land deposited by running water.
The northern half of the province is flat, and even marshy along the coast, and consists of a broad band of alluvium formed by the series of parallel rivers descending from the south.
Korean soil consists largely of light sandy loam, disintegrated lava, and rich, stoneless alluvium, from 3 to 1 0 ft.
The finer material constituting alluvium, often described as "silt," is sand and mud.
The mud brought down by it, calculated at 7150 lb an hour at Bagdad, is not deposited in marshes to form alluvium, as in the case of the Euphrates, but although in flood time the river becomes at places an inland sea, rendering navigation extremely difficult and uncertain, the bulk of the mud is deposited in banks, shoals and islands in the bed of the river, and is finally carried out into the Persian Gulf.
The coast, constantly encroaching on the sea by reason of the alluvium washed down by the rivers of the Pyrenees and Cvennes, is without important harbours saving that of Cette, itself continually invaded by the sand.
The first of these canals, taken off on the right bank of the river a little below Hit, followed the extreme skirt of the alluvium the whole way to the Persian Gulf near Basra, and thus formed an outer barrier, strengthened at intervals with watch-towers and fortified posts, to protect the cultivated land of the Sawad against the incursions of the desert Arabs.
It is easy to distinguish the great primitive watercourses from the lateral ducts which they fed, the latter being almost without banks and merely traceable by the winding curves of the layers of alluvium in the bed, while the former are hedged in by high banks of mud, heaped up during centuries of dredging.
Much of the Triassic area is covered superficially by glacial drift and alluvium of the Trent.
Reclaimed marsh-land and fresh alluvium (the so-called " front-lands " on rivers and bayous) are choice soil for Indian corn, sugar-cane, perique tobacco, semi-tropical fruits and cotton.
Albert Nyanza, on the other hand, is threatened in the distant future with destruction from another cause - the filling of its bed by the alluvium poured into it by the Semliki, the Victoria Nile and, in a lesser degree, by other streams. The Semliki receives directly or indirectly the whole of the drainage of Ruwenzori, and also that of the eastern face of the Congo mountains as well as the drainage basin of Albert Edward Nyanza.
The main deposits of alluvium occur below Lambeth and Westminster, and in the valley of the Wandle, which joins the Thames from the south near Putney.
It naturally falls into two divisions, the northern being more or less mountainous, while the southern is flat and marshy; the near approach of the two rivers to one another, at a spot where the undulating plateau of the north sinks suddenly into the Babylonian alluvium, tends to separate them still more completely.
Such river-transported material or alluvium is common in all river valleys.
In the alluvium which covers all, the remains have been discovered of several species of elephant, which, according to Dr Edmund Naumann, are of Indian origin.
The Coastal Plain has for the most part a light sandy soil, but there is a fertile alluvium in the river bottoms and good clay soils on some of the uplands.
These branches enclose a deltaic formation, a low tract of marshy alluvium known as the Lezirias, traversed by several minor channels.
In the larger valleys and along the shores of lakes considerable alluvium is mixed with this clay.
Calculating from the present rate of deposit of alluvium at the head of that gulf, Eridu should have been founded as early as the seventh millennium B.C. It is mentioned in historical inscriptions from the earliest times onward, as late as the 6th century B.C. From the evidence of Taylor's excavations, it would seem that the site was abandoned about the close of the Babylonian period.
West of the Missouri river the drift gives place to a fine soil of sand aid clay, with deposits of alluvium in the vicinity of streams. Though lacking in vegetable mould, these soils are generally capable of producing good crops where the water-supply is sufficient.
The best soils are the alluvium in the bottom-lands along some of the larger rivers and that of the Blue Grass Region, which is derived from a limestone rich in organic matter (containing phosphorus) and rapidly decomposing.
The greater part of Bechuanaland is covered with superficial deposits consisting of the sands of the desert regions of the Kalahari and the alluvium and saliferous marls of the Okavango basin.
Many shallow lakes have been completely filled with alluvium and their sites are now occupied by fertile plains; this process may be seen in operation almost anywhere; a good illustration is the delta of the Rhone in Lake Geneva.
(7) The section of south Sumatra between the eastern chain of old rocks and the east coast with its numerous river mouths is formed of the alluvium of sea and rivers.
The more modern deposits of Holland consist of alluvium, wind-blown sands and peat.'
The earlier geologists had been in the habit of dividing the Quaternary deposits into an older Diluvium and a younger Alluvium; the latter is still employed in England, but the former has dropped out of use, though it is still retained by some continental writers.
The Alluvium was distinguished from Diluvium by the fact that its mammalian fossils were representatives of still living forms, but it is a matter of great difficulty to separate these two divisions in practice.
But in the " Drift " maps many other types of deposit are indicated, such, for instance, as the ordinary modern alluvium of rivers, and the older river terraces (River-drift of various ages), including gravels, brickearth and loam; old raised sea beaches and blown-sand (Aeolian-drift); the " Head " of Cornwall and Devon, an angular detritus consisting of stones with clay or loam; clay-with-flints, rainwash (landwash), scree and talus; the " Warp," a marine and estuarine silt and clay of the Humber; and also beds of peat and diatomite.
The flood waters of the Chambezi and other streams, which deposit large quantities of alluvium, are gradually solidifying the swamp, while the Luapula is believed to be, though very slowly, draining Bangweulu.
In some rivers the water is generally pure; in others it is highly charged with fertilizing alluvium, or, it may be, with barren silt.
The second is hardly less valuable, and consists in the remarkable richness of the alluvium brought down the river year after year during the flood.
The Guadalquivir basin is likewise divided by the configuration of the ground into a small upper portion of considerable elevation and a much larger lower portion mainly lowland, the latter composed from Seville downwards of a perfectly level and to a large extent unhealthy alluvium (Las Marismas).
Seistan Proper is an extensive tract of sand and clay alluvium, generally flat, but irregular in detail.
Alluvium; travertine; coral; sand dunes; continental dunes.
Of a river, a rich deposit of black alluvium on valley bottom lands, a belt of red clay loam on uplands S.
In eastern Oregon the soils are of an entirely different type, being usually of a greyish appearance, lacking in humus, and composed of volcanic dust and alluvium from the uplands.
Here then, buried in alluvium at a depth of 50 to 60 ft.
The remains of a gigantic ox, Bubalus Baini, have been obtained from the alluvium near the Modder river.
The great thickness of the Gangetic alluvium is shown by a borehole at Calcutta which was carried to a depth of about 460 f t.
The floor of the Basin Region is formed of alluvium washed from the high plateaus and mountain ranges, a part of which has accumulated in alluvial fans, and part in the greatly expanded lakes which existed here in the glacial period.
This alluvium gives gently sloping or level desert plains, from which isolated mountain ranges rise like islands from the sea.
Soil.-The alluvium of the desert basins furnishes much good soil, which produces abundant crops where irrigated.