Modern Geography

s called "normal erosion," to distinguish it from that other form of surface moulding in which ice and frost play a prominent part. At the present time ice, in the form of ice-she

ice is very recent, and that during a period which geologically is only

much of North America, and, probably, considerable parts of the southern hemisphere, were subjected to the action of ice so re

s sometimes form great sheets of boulder clay; sometimes they are collected into the curious sandy and gravelly mounds called kames which in parts of, e. g. Scotland, have a great extension; sometimes they have formed great heaps of material at the entrances of vall

North America, have been recently clad in ice is associated with many peculiarities of surface fo

tate at once that this study has been largely stimulated by the fact that there is at present a great want of unanimity of opinion as to the exact cause of these peculiarities of form. Accor

culiar features of glaciated regions in the way in which running water works when it is controlled and modified by the existence of i

n for the geologist. It is, however, of great importance to the geographer that recently glaciated surfaces should be studied from every point of view, for from this detailed study are emerging man

rs. Thus we find that most of the text-books emphasise the occurrence of perched blocks, of erratics, i. e. of blocks of rock which must have been carried from a distance, of the phenomenon of crag and tail, of giants' kettles, and so on. All these are of more geological than geographical importance; they do no

the peculiar features of the valleys in recently-glaciat

he forces work the more nearly is the valley floor reduced to an even slope, whose angle decreases in passing from the mountain to the plain track. In the

hat is, there is no sharp discordance between the two. While, however, the "mature" river valley shows a gentle, continuous slope, we usually fin

asily eroded than others. These form waterfalls, which ultimately, as we have seen, give place to gorges. Beyond the waterfall the diminishing slope

as we have seen, in a collecting basin, which receives the surface runne

scribed in the volume on the Alps, and further, photography and the picture postcard have rendered the main features of a glacier fa

ondition described as U-shaped to point the contrast with the river valley. Examples in Great Britain and elsewhere are frequent, but some of the Alpine valleys show the phenomenon in a very striking fo

side of the broad, flat valley floor, and from the summit of this cliff the lateral streams leap into the main valley by often superb waterfalls. This is a very important featu

hile the main valley is said to be over-deepened. The rocky height over which the water springs may be call

he Alpine villages with electricity, and in driving the trains which often carry the tourist to those villages. In the French and Italian Alps especially, t

unded forms due to ordinary weathering. BC, the shelf or shoulder, formerly covered by the ice, and therefore strewn with glacial débris. It now usually forms a pasture or

ve noticed a peculiar and often trying feature of any walk which leads up the side of the valley. This is that the walk begins with a very steep ascent, where the road or track zig-zags to and fro. After this steep and trying climb the walker reaches a broad shelf (BC in

ge of the cliff wall over which the streams leap in cascades. A is the position of the stream at the bottom of the U-shaped

, however, his walk has been to see a famous waterfall from above, and he will find that the streams which flow with relative slowness over the compa

iscuss the probable causes of this striking "break of slope," so different from the characteristically continuous slopes of an ordinary mature river valley. As has been indicated, it is here that active controversy rages

oil. The fertile soil, which is often irrigated by milky water from existing glaciers, combined with the effec

c arm-chair-shaped notches, high up on the mountain sides, which the Welsh call cwms, the Scotch corries, the French cirques, and the Germans kare, are very widespread in the Highla

s, if several cirques occur near together, the side walls may be eroded through, so that a shelf is produced, as one might produce a bench by putting two chairs side by side, and cutting away the contiguous arms. Very often, as one may easily see in the Highlands o

m showing two

e topmost of such a series of cirques still retains a glacier, what is c

stic U-shaped rounding characteristic of glacial forms. Further, at the top of the wall of the trough a bench or shelf exists, which is obviously the remains of the old cirque floor. In the case of all characteristic glacial cirques, however, the special feature is that the flat bottom of t

egions, and especially in Great Britain. There are two views as to their origin, and we shall indicate both here without making any attempt to decide which is the correct one. A very full and clear statem

rt of the glacier disappeared and only the cirque glacier was left. It continued its protective action, while below the powerful torrents hollowed out a trough. This process was perhaps repeated several times, with the final result that the protected cirque was left as a much-modified remnant of pre-glacial conditions, while the valley below was powerfully eroded by the glacial torrents. Thus a cirque lying above an existi

-glacial mountains. Cirques are believed to have been produced by the ice wherever the form of the mountains conduced to the accumulation of snow, and the occurrence of a series of cirques, and of the troughs

the main valleys, but, further, this main valley itself often consists of relatively level reaches alternating with rocky bars, through which the river has som

utting a tiny gorge. If the tourist crosses the lake in a boat and begins to walk up the valley above it, he will find that it has the form of a staircase, the huge steps being separated from one another by broad plateaux, which are flat and swampy, and have obviously

rland, to show the staircase arrangement peculi

illage. The intervening region or step is too rocky to give level ground for human habitations or for pasture and cultivation. Where the river has had time to cut a gorge, the road must leave the stream, and can often be constructed only with difficulty. The result is that an Alpine valley often consi

ile the torrent which issued from it eroded very rapidly below; according to another school the landings are due to direct glacial erosion. There are other observers, again, who lay especial stress upon the modifications of the erosive powers of running water, due to the presence of the ice. For us it is of interest to notice that, as has been already indicate

iated. In the geography books and in some maps, the Alps, for example, are represented as a great barrier, shutting off the fertile plains of Italy from the countries of Central Europe. But history shows that they

st not forget that in addition to these and the other great passes there are almost innumerable ways of crossing the Alps on foot, and the presence either of Hospices or of small inns on many of the smaller passes shows that they are constantly used at the pr

n steeper on the Italian than on the other side, then a broad, windswept, open summit, sometimes almost le

uch connections between two drainage systems (that is, the existence of a very low divide between the two) only exist on a small scale outside glaciated regions, so that they, with all their effects upon communications, must be largely ascribed to ice-action.

hich the path enters at the village of Leuk. The walk proper is, however, over at the Baths of Leuk, a small health resort lying at the foot of the great Gemmiwand, a wall of rock over 1,600 feet in heigh

ch is shrinking and exposing more and more of its old bed. Even to the most inexperienced traveller it is obvious that this present day shrinkage is, as it were, the last remnant of a shrinkage which has been going on for a prolonged period, so that the route by which the traveller ascended from Kandersteg is but a remnant of the bed of the old glacier. The point of special interest, however, is that at the end of the Daubensee the traveller leaves the glacial valley by which he has ascended, and passi

the valley wall, down into the Rhone valley. This tongue of ice, either by its own erosive power, or because of the glacial and sub-glacial streams which it produced, wore out a notch in the wall as it crossed, and it is this notch which makes the pass. As the glacier gradually shrank, it could no longer send this tributary over the wall into the valley be

asses are likely to be frequent across their hills and valleys, owing to the power which ice possesses, when enormously developed, of rising above valley walls, and streaming down into

utary streams leap is a shelf, which is clearly a portion of the floor of the pre-glacial valley and is covered by glacial débris. At the heads of the valleys there are often cirques or plateaux, which again are markedly discordant, hanging high above the

an equally obvious discordance, a discontinuity of slope, most marked where water has not had time to begin its smoothing action. As every glaciated valley which we can study in detail has been subjected to the action both of ice and of water, it is a simple deduction that the discontinuity is due to the d

d distribution of plants and animals throughout the areas affected. Obviously the covering of ice must have rendered a large part of Europe uninhabitable both for man and for the vast majority of animals and plants. In Europe,

orida almost touches the tropic, and Mexico extends far beyond it. In this continent, therefore, the plants and animals, though driven far to the south, still found room to live

regions are very rich in species and in genera. It is believed that this rich North American flora is a remnant of pre-glacial conditions, and

en as a wild tree in many parts of the continent of Europe, was introduced from China, while the beautiful Sophora japonica, so frequently planted in towns, comes, as its name indicates, from Japan, and the various species of those beautiful flowering trees known as Catalpa are either American or Asiatic. The western plane (Platanus occidentalis), another favourite town tree, comes from the United States, and other American trees which are found very abundantly in towns in the warmer parts of Europe are the black walnut and the honey locust (Gleditschia tricanthos). Perhaps more striking than any of th

must have been obstacles in the way of the southern migration alike of plants and of animals. Again, even if these obstacles were passed or turned, the great inland sea formed another barrier further south. In consequence of this difficulty in finding asylums the pre-glacial plants and animals must have perished

from the south and from the east. We shall indicate later how man himself came from the south and the east to colonise