These minor ranges, excepting the Zenta, are separated from the Andean masses by comparatively low depressions and are usually described as distinct ranges; topographically, however, they seem to form a continuation of the ranges running southward from the Santa Victoria and forming the eastern rampart of the great central plateau of which the Puna de Atacama covers a large part.
South of the Bermejo the land is more elevated and drier, though large depressions covered with marshy lagoons are to be found, similar to those farther north.
The water-courses and depressions of the shingly steppes afford pasturage sufficient for the guanaco, and in places support a thorny vegetation of low growth and starved appearance.
Lake Torrens, the largest of these depressions, sometimes forms a sheet of water 100 m.
The cells belonging to any given thread may be recognized at an early stage of growth, because each cell is connected with its neighbors belonging to the same thread by two depressions or pits, one at each end.
According to Lecointe, the young wall consists partly of cellulose and partly of a substance which is not cellulose, the latter existing in the form of slight depressions, which mark the position of the future pores.
Wide areas, giving rise to oceanic depressions and leaving the continents protuberant; the other, folding along comparatively narrow belts, giving rise to mountain ranges.
Within this space three depressions, all running S.W.
The depressions which gap the borders of the central plateau thus acquire a greater importance than the small differences in its vertical elevation.
Not a tree is to be seen, the few woods and thickets being hidden in the depressions and deep valleys of the rivers.
Innumerable clusters of wild cherries (Prunus Chamaecerasus), wild apricots (Amygdalus nana), the Siberian pea-tree (Caragana frutescens), and other deep-rooted shrubs grow at the bottoms of the depressions and on the slopes of the ravines, imparting to the steppe that charm which manifests itself in the popular poetry.
Some rivers, notably the Kur (Kyros, Araxes) which flows into the Bakhtegan lake east of Shiraz, drain into inland depressions or lakes.
On the one hand he may make the line follow the natural inequalities of the ground as nearly as may be, avoiding the elevations and depressions by curves; or on the other he may aim at making it as nearly straight and level as possible by taking it through the elevations in cuttings or tunnels and across the depressions on embankments or bridges.
An embankment-bank, or fill, is the reverse of a cutting, being an artificial mound of earth on which the railway is taken across depressions in the surface of the ground.
The kavirs, or salt depressions, of the Persian desert are more frequently widespread deposits of mud and salt than water-covered areas.
Although for the purposes of geographical nomenclature, boundaries formed by a coast-line - that is, by depressions of the earth's solid crust below the ocean level - are most easily recog- Political nized and are of special convenience; and although such divisions.
There are, it is true, mountain ranges which are formed of folded beds; but in many cases the direction of the chains is different from that of the folds, so that the ranges must owe their elevation to other causes; and the folds, moreover, are of ancient date, for the most part Archaean or Palaeozoic. The configuration of the region is largely due to faulting, trough-like or tray-like depressions being formed, and the intervening strips, which have not been depressed, standing up as mountain ridges.
Structurally, the folds of this region are of ancient date; but the area is crossed by a series of depressions formed by faults, and the intervening strips, which have not been depressed to the same extent, now stand up as mountain ranges.
They are found one on each cephalic tentacle, and are simply minute open pits or depressions of the epidermis, the epidermic cells lining them being pigmented and connected with nerves (compare fig.
The recognition of these, minute and fragmentary as many were, and the referring them to their proper place, rendered necessary an attentive study of the comparative osteology and myology of birds in general, that of the " long bones," whose sole characters were often a few muscular ridges or depressions, being especially obligatory.
The most striking feature in the structure of Syria is the existence of long Graben, or narrow depressions formed by faulting.
The faulting which formed the depressions is certainly later than the deposition of the Cretaceous beds and probably belongs to the later portion of the Tertiary era.
They are due largely to sinkholes or depressions caused by solution of the limestone of the region.
The depressions between the ridges are not filled up with cement.
Molecular Depressions of the Freezing Point.
There are, however, among these border-ranges several breaches of continuity - broad depressions or trenches leading from Lake Balkash and Lake Zaisan to the upper parts of the plateau.
All the valleys and depressions bear traces of immense post-Pliocene lakes.
The shores of all the lakes which filled the depressions during the Lacustrine period abound in remains dating from the Neolithic Stone period; and numberless kurgans (tumuli), furnaces and so on bear witness to a much denser population than the present.
In Magellania [Waldheimia] it is elongated and reflected; the hinge-plate large, with four depressions, under which originates a median septum, which extends more or less into the interior of the shell (figs.
H, Epidermic cell-layer; mes, mesoblastic connective tissue; n, nerves; II, III, IV, V, depressions of the epidermis in each of which a cuticular lens will be formed.
In the larger depressions, like that of the Reconcavo of Bahia, there are large alluvial areas celebrated for their fertility.
Neither of these " depressions," however, penetrates beyond 94° E., and on the route from Kiakhta to Su-chow, in 100° E., there is only one.
Small springs of fresh water are frequent and there are 'several shallow lakes or pans - flat bottomed depressions with no outlet.
The surrounding tissue enlarges, so that the spots appear as if sunk in depressions, and bear a considerable resemblance to hailstone wounds.
It is, however, a region of past volcanic activity, and these salt depressions may be due to that cause.
Only for the intervention of man these rivers would at all times find their way into the adjoining depressions, which they would maintain as lakes of water.
Some are contained in alluvial depressions in the river valleys; others have been formed by volcanic eruptions, the ejecta damming the rivers until exits were found over cliffs or through gorges.
They owe their origin to depressions of the earth's crust of no very wide extent and not running very far into the continental mass, and geologically they are of recent age and still subject to change.
In these respects they contrast with the great oceans which owe their origin to the most extensive and the profoundest depressions of the crust, date back at least to Mesozoic times, and have perhaps remained permanently in their present position from still remoter ages.
The former are either the extensions of oceanic depressions, e.g.
The Arabian Sea, Bay of Bengal and Gulf of Arica, or such caldron-depressions as the Gulfs of Genoa and Taranto, or rift-depressions like the Gulfs of Aden and Akaba.
Troughs and basins in the middle of the ocean, (2) the steeply sloping ridge which interposes a narrower barrier between two depressions, and (3) the plateau or wide elevation rising steeply on all sides from a depression.
Strong evidence of this is afforded by the association of some of the depressions, notably the Japan Trench and the Atacama Trench, with the origin of frequent submarine earthquakes.
The Baltic Sea exceeds 50 fathoms in few places except the broad central portion, though small caldron-like depressions here and there may sink below zoo fathoms. The Red Sea on the other hand, though shut off from the Indian Ocean by shallows of the Strait of Bab-elMandeb with little more than ioo fathoms, sinks to a very considerable depth in its central trough, which reaches 1209 fathoms in 20° N.
It is a remarkable geographical fact that on the rises and in the basins of moderate depth of the open ocean the organic oozes preponderate, but in the abysmal depressions below 2500 or 3000 fathoms, whether these lie in the middle or near the edges of the great ocean spaces, there is found only the red clay, with a minimum of calcium carbonate, though sometimes with a considerable admixture of the siliceous remains of radiolarians.
Sir John Murray believes that no more than a few feet of red clay have accumulated in the deepest depressions since the close of the Tertiary period.
The northern half is more broken and irregular; elevations, usually rounded, mingle with depressions some of which are occupied by small shallow lakes or ponds, the characteristic physical features of this region being due to glaciation.
In formation it resembles the limestone Alps of Tirol and there are on its elevated plateaus a number of doline or funnel-shaped depressions into which the melted snow and the rain sink.
The principal rivers are the Mashkid and that of Bampur which flow away from the sea and are lost in depressions called hamuns.
To the east the valley is characterized by swamps and forests, but to the west the natural depressions freely carry off the surface drainage.
Large and valuable deposits of the sand have been obtained in sinks and depressions on the surface of the chalk.
In numerous depressions, some of which may have been the beds of lakes formed by beaver dams, the soil is deep and largely of vegetable formation.
Behind the Tell is a lofty table-land with an average elevation of 3000 ft., consisting of vast plains, for the most part arid or covered with esparto grass, in the depressions of which are great salt lakes and swamps (Arabic, shats) fed by streams which can find no outlet to the sea through the encircling hills.
To the Pliocene period the marine deposits of the Sahel of Algiers and of the Sahel Jijelli must be attributed; also the lacustrine marls and limestone of the basin of Constantine, and the ancient alluviums of the basins and depressions which bear no relation to the existing valleys.
The average depth varies from 1500 to 2500 fathoms, and from this level innumerable volcanic ridges and peaks rise almost or quite to the surface, their summits for the most part occupied by atolls and reefs of coral formation, while interspersed with these are depressions, mostly of small area, among which the deepest soundings recorded have been obtained.
In the north-west, and is generally much less rugged than the Alleghany Plateau; a peculiar feature of the southern portion of it is the numerous circular depressions (sink holes) in the surface and the cavernous region beneath.
The Hohe Tauern contains many high lying valleys, traversed by the streams which flow into the Salzach, as well as numerous depressions and passes, here called popularly Tauern.
Deperet points also that we owe to Cuvier the first clear expression of the idea of the increasing organic perfection of all forms of life from the lower to the higher horizons, and that, while he believed that extinctions were due to sudden revolutions on the surface of the earth, he also set forth the pregnant ideas that the renewals of animal life were by migration from other regions unknown, and that these migrations were favoured by alternate elevations and depressions which formed various land routes between great continents and islands.
The two noteworthy depressions in its surface, the Valley of Mexico and Bolson de Mapimi, once contained large bodies of water, of which only small lakes and marshy lagoons now remain.
They may be divided into two classes; those of the plateau region which occupy lacustrine depressions and receive the drainage of the surrounding country; and the tide-water lagoons of the coast formed by the building up of new sand beaches across the indentations in the coast-line.
Conifera; the star represents the ciliated cup connected by ciliated depressions with the groove; 5, disk of Conochilus, like the Bdelloid, but with mouth antero-dorsal, the gap postero-ventral; 6, disk of Stephanoceroscingulum broken up into setiferous lobes, groove a naked funnel, trochus a horseshoe-shaped ridge, mouth central.
In the northern region are large marshy depressions, in which the water is often salt.