[Aprin 18, 1912 
180 NATORE 
western Sweden. They agree with rias by having 
curved lines, gentle slopes, and indented shores. 
They differ, however, from rias, as they often include 
deep basins, separated by rock bars from the outer 
sea, which may not for some distance reach the depth 
of the inner basins. Fiards, moreover, usually have 
no large rivers draining into them, and may receive 
only insignificant streams and brooks. Fiards are 
due to a lowland area with an irregular surface of 
hard rocks having been partially submerged beneath 
the sea. The essential difference from fiords is that 
fiards are characteristic of the coast lands which rise 
to but a slight height above sea-level. 
The third group consists of the fiords, which, seen 
from a steamer or on an ordinary map, have seven 
chief characters. 
(1) They are typically long, straight, narrow 
channels, and they are usually so crowded and run 
so far inland that they add greatly to the length of 
the coast line. Thus, whereas in Norway the length 
of the coast from headland to headland is 1700 miles, 
the actual length of the shore line along the fiords 
is 12,000 miles. 
(2) The walls are typically high and steep. 
(3) The fiord channels usually have parallel sides, 
and the fiords bend or branch at sharp angles, and 
the same angle tends to recur throughout a district. 
There is accordingly a striking parallelism in the 
geographical elements of neighbouring fiords. 
(4) The fiord valleys are often arranged along inter- 
secting lines like a network of cracks, in contrast 
to the converging tributaries of a river system. 
(5) The fiords are characteristic of dissected 
plateaus. All the great fiord districts of the world 
were formerly plateaus. 
(6) Owing to the plateau structure the land extends 
backward from the fiord walls with gentle slopes and 
shallow valleys. Streams flow gently across these 
uplands until they reach the fiord wall, and then 
plunge down it in great waterfalls, which are 
especially picturesque in spring, when the rivers are 
flooded by the melting snow. The highest waterfall 
in the world, the Sutherland Falls of New Zealand, 
sometimes leaps, it is said, in one jump of tgoo ft. 
on to the floor of the fiord valley of Milford Sound. 
The upland valleys which join the fiords have not 
been cut down to the level of the main valley, but 
enter abruptly high upon its side. They are there- 
fore ‘‘hanging valleys.” 
(7) Finally, the amount of land beside the 
suitable for cultivation is usually limited to small 
tracts at the head of the fiord or on small deltas 
along its sides. The amount of cultivable land in a 
fiord district is small, and fiord countries are there- 
fore sparsely populated. One of their main values 
will be as the playgrounds for more crowded countries. 
They sometimes have rich mineral deposits, as in 
Alaska; but many American authorities claim that 
even there the scenery will prove the most valuable 
economic asset. 
The previous characters can be observed by a 
tourist from the deck of a steamer, but if we could 
remove the sea and travel over the fiord floors three 
fresh geographical features would be revealed. : 
The walls which rise high above the sea surface 
would be seen to descend steeply to extraordinary 
depths. The deepest known fiord is the Messier 
Channel, in Patagonia, which reaches the depth of 
4250 ft. The Sogne Fiord is the deepest in Europe, 
with the depth of 3780 ft. Some of the lakes which 
may be regarded as inland extensions of fiords are 
also surprisingly deep. Thus Lake Morar, in the 
western Scottish Highlands, of which the surface is 
22 ft. above sea-level, is 1017 ft. deep; and this fact 
NO. 2216, VOL. 89] 
fiords 
is all the more striking as the sea to the west does 
not reach that depth within the distance of 120 miles. 
The deepest part of a fiord basin is usually at some 
distance from the sea; the floor rises seaward until 
it is covered only by shallow water, or projects above 
the surface and the fiord becomes a lalxe. 
Fiords are therefore often separated from the outer 
sea by submerged thresholds. This fact was first 
discovered by Captain Cook in Christmas Sound, 
Patagonia; he found to his danger that on passing 
up that fiord he lost the anchorage which he had 
at its mouth. The existence of a threshold is such 
a frequent feature of fiords that it is regarded by 
some authorities as an essential character. 
The removal of the water from a fiord would show 
that it has a flat floor. The valley is trough-shaped, 
whether empty or partially filled with water. The 
flatness of the floor can be learnt by cross sections 
from charts, or seen on the floor of the undrowned 
part of a fiord valley. 
The problem presented by fiords is therefore that 
of the formation of systems of steep trough-valleys, 
which are arranged in networks so that the land 
beside them is broken up into rectangular blocks, and 
usually have deep inner basins separated from the sea 
by shallow thresholds. 
The simplest explanation of valley formation is 
excavation by rivers; but this process will not explain 
the origin of fiords. Thus our British fiords, the 
Scottish sea-lochs, are not on river valleys; of the 
chief Scottish rivers, the Tay and the Forth. enter 
the sea through rias; the Clyde discharges into a 
compound basin which is not a fiord; and the Tweed, 
Dee, Don, and Doon have no long arms of the sea 
at their mouths. The chief sea-lochs, on the other 
hand, receive only small streams. The river systems 
of Scandinavia, North and South America, and New 
Zealand show the same independence of the fiords. 
The fiords are not the outlets of the main rivers. 
In fact, so far from fiords being made by rivers 
their existence depends on the absence of rivers, which 
would convert them into ordinary valleys by wearing 
back their banks and filling the main channel with 
sediment. 
The failure to explain the formation of fiords by 
rivers of water therefore led to the invocation of 
rivers of ice, and many features of the fiord valleys 
are consistent with their formation by glaciers. The 
essential difference between the action of water and 
ice as agents of excavation depends on their differ- 
ence in plasticity. Water, being very plastic, readily 
; adapts itself to the irregular resistance of the adjacent 
rocks; it glances lightly off opposing hard surfaces 
and carves for itself sinuous channels. 
Glacier ice flows around opposing obstacles, but as 
it is less plastic than water it is deflected less readily 
and bears with persistent pressure against the rocks 
in its path, and if armed with stones and grit it 
wears away the rocks like a grindstone. Therefore, 
whereas denudation by water tends to develop 
rounded surfaces with curved lines, ice, when con- 
fined in valleys, tends to produce straight lines, flat 
slopes, and angular, facetted surfaces. 
The difference between the rounding action of 
water and the facetting action of ice may be illus- 
trated by reference to the typical forms of pebbles in 
deposits laid down by rivers and by ice. The typical 
river pebble is rounded, and often egg-shaped. The 
typical ice-worn rock in a boulder clay has flattened 
| surfaces. which often meet sharply along straight - 
edges, like the facets of a gem. The same differences 
can be recognised on a larger scale in the topography 
of a glaciated district. 
Further, a river flows around the base of the spurs 
