That the mountainous mass of western Maui is much older is shown by the destruction of its crater, by its sharp ridges and by deeply eroded gorges or valleys.
At some period, long subsequent to its original excavation, and after many large stalactites had grown, it was completely filled with glacial mud charged with acid, whereby the dripstone was eroded into singularly grotesque shapes.
Corner of Arizona is a region of greatly eroded ranges and gentle aggraded valleys.
The " bluffs " (remnants of an eroded plain formed of alluvion deposits over an old, mature and drowned topography) run through the second tier of parishes W.
The most striking feature of the embayment is the broad valley which the Mississippi has eroded across it.
In this part of its course the Euphrates runs through an open, treeless and sparsely peopled country, in a valley a few miles wide, which it has eroded in the rocky surface.
The hilly aspect of several parts of the central plateau is not due to foldings of the strata, which for the most part appear to be horizontal, but chiefly to the excavating action of the rivers, whose valleys are deeply eroded in the plateau, especially on its borders.
The surface of Minas Geraes is broken by mountain ranges and deeply eroded rivercourses, the latter forming fertile valleys shut in by partly barren uplands, or campos.
On the north there is little coastal plain except at the mouths of rivers, but on the south coast there is a plain of considerable extent broken only by the remains of eroded foothills.
When the warmer interglacial periods recurred the polar and continental ice-caps melted and the sea-level became raised again - that is, there was submergence of the eroded plateaux formed as indicated above.
These new structures would rest uncomfortably upon eroded formations and this, Wayland Vaughan points out, is what we actually observe in the case of living and fossil coral reefs.
The Brazilian plateau slopes southward and eastward, traversed by broken ranges of low mountains and deeply eroded by river courses.
Above the sea-level, traversed by two great mountain systems, and deeply eroded and indented by numerous rivers.
The remainder of the state which lies east of the Tennessee river is divided into the Highland Rim Plateau and a lowland basin, eroded in the Highland Rim Plateau and known as the Blue Grass Region; this region is separated from the Highland Rim Plateau by a semicircular escarpment extending from Portsmouth, Ohio, at the mouth of the Scioto river, to the mouth of the Salt river below Louisville; it is bounded north by the Ohio river.
At the highest point of the transisthmian railway), but their general elevation is much lower, and they are broken by wooded sierras and eroded by water-courses.
When the oldland and its overlap of stratified deposits were elevated again, the overlapping strata must have had the appearance of a coastal plain; but that was long ago; the strata have since then been much eroded, and to-day possess neither the area nor the smooth form of their initial extent.
The lakes were small at first, and each had its own outlet at the lowest depression in -the height of land to the south; but as the ice melted back, neighboring lakes became confluent at the level of the lowest outlet of the group; the outflowing streams grew in the same proportion and eroded a broad channel across the height of land and far down stream, while the lake waters built sand reefs or carved shore cliffs along their margin, and laid down sheets of clay on their floors.
The outlet of this glacial lake, called river Warren, eroded a large channel in which the Minnesota river, of to-day is an evident misfit.
On some of these channels deep gorges were eroded heading in temporary cataracts which exceeded Niagara in height but not in breadth; the pools excavated by the plunging waters at the head of the gorges are now occupied by little lakes.
The great river flows through the semi-consolidated strata of the plain, in which it has eroded a valley, 40 or 50 in.
This mountain mass is of flat-arched, dome-like structure, now well dissected by radiating consequent streams, so that the weaker uppermost strata have been eroded down to the level of the plains where their upturned edges are evenly truncated, and the next following harder strata have been sufficiently eroded to disclose the core of underlying crystalline rocks in about half of the domed area.
When, the region was broken into fault blocks and the blocks were uplifted and tilted, the back slope of each block was a part of the previously eroded surface and the face of the block was a surface of fracture; the present form of the higher blocks is more or less affected by erosion since faulting, while many of the lower blocks have been buried under the waste of the higher ones.
This widespread submergence, followed by the deposition of marine sediments on the eroded surface of Comanchean and older rocks, is the physical reason for the separation of the system from the Comanchean.
The largest and southernmost, a broad belt extending from the " fall-line " to a line passing through Clarkesville, Habersham county, Cartersville, Bartow county and Buchanan, Haralson county (approximately), is known as the Piedmont Belt or Plateau, being a region of faint relief eroded on highly complicated crystalline rocks.
Jebel Akhdar, being without "faults," has no deep internal valleys, and presents, the appearance of downs: but its seaward face is very deeply eroded, and deep circular sinkings (swallow-holes) are common.
That those to the westward have long been inactive is shown by the destruction of craters by denudation, by deep ravines, valleys and tall cliffs eroded on the mountain sides, especially on the windward side, by the depth of soil formed from the disintegrated rocks, and by the amount as well as variety of vegetable life.
For here five large glaciers united to form the grand trunk glacier that eroded fhe valley and occupied it as its channel.
Both of these ranges of hills are composed of hard crystalline rocks, and between them lies the lowland eroded on the weaker sandstones and sediments.
The plains on the east and west lie at a lower level and are eroded by larger rivers, clothed with forest, showing more sawahs and ladangs, or dry ricefields, and, near the rivers, planted with jagong (maize), coffee and fruits.
When the land reappeared a new series of valleys would at once begin to be eroded; and the subsequent degradation of these overlying sediments might reveal portions of the older topography, as in the case of the Great Glen, Lauderdale, and other ancient valleys.
After the mud had been mostly removed by flowing water, these eroded forms remained amid the new growths.
To the strike, and cutting through opposed escarpments by deep valleys, and those following the line of strike along a bed of easily eroded rock.
Separating the plateau from the mountain region is an abrupt 'transition slope, often deeply eroded, crossing the entire state as has been indicated.
From these beds up to the top of the Carboniferous there appears to be no break; but the Carboniferous beds were in some places eroded before the deposition of the Productus shales, which belong to the Permian period.
Shales occur, and the passage of the streams through deep rifts or gorges across the hard limestone anticlinals, which stand in irregular series of parallel ridges with the eroded valleys between.
Here the sea has greatly eroded the normal regular, harbourless line of the west coast of Africa, forming bold capes and numerous inlets or estuaries.
The mountains in fact have been hewn out of the original bulk of the land in proportion as the valleys have been excavated_ The denudation would continue so long as the ground stood above the level of the sea; but there have been prolonged periods of depression, when the ground, instead of being eroded, lay below the sea-level and was buried sometimes under thousands of feet of accumulated sediment, which completely filled up and obliterated the previous drainage-lines.
Much discussion has arisen as to their mode of origin, but it is probable they were caused by the erosive action of ice, since glaciers occupied the glens where they occur and wore down the rocks along the sides and bottom; but it is a point of difficulty in this theory whether ice could have eroded the deepest of the hollows.
The west side, as we have seen, has been more deeply eroded than the eastern.
In the Isle of Eigg, for example, the basalts had already been deeply eroded by river-action and into the river-course a current of glassy lava (pitch-stone) flowed.
The banks of the Nile and the islands in it are subject to gradual but constant alterationindeed, several ancient sites have been much eroded or ~destroyedand the main volume of the stream may in course of time be diverted into what has previously been a secondasy channel.
In the east a tableland of sandstone, called Saxon Switzerland, from the picturesque outlines into which it has been eroded, adjoins the Erzgebirge; one of its most notable features is the deep ravine by which the Elbe escapes from it.