THE GEOLOGY OF .FIORDSA
IN his new book—a sequel to his Greet Rift Valley—t)r. Gregory makes a very- interesting contribution to what may be called the higher geology,' that branch of • the 'science which concerns itself with the great questions of the shaping of the earth and the moulding of landscape. The Norwegian fiords, with' their allied formations in maul' parts of the world, from the sea lochs of the Western Highlands to Milford Sound in New Zealand, present a very well marked and characteristic type of scenery, which is particularly interesting to the layman because of the-great influence which it has exerted on the destinies of mankind. It was on the Norwegian fiords that originated-" the facility of -intercourse by sea which marks the most influential difference between modern and mediaeval-Europe." The beginnings of modern seamanship, as Dr. Gregory points, out, may be traced. to the fiords, which were the only practicable highways open to our Norse ancestors. It is then with more than merely speculative interest that the citizens of an Empire which is the outcome and child of sea.power may study the question of the origin of the fiords, to which Dr. Gregory has devoted many years of research, and of -which he now offers a theory which will probably be accepted by geologists at large in view of the great mass of evidence from all parts of the world which he marshals and discusses in this weighty A true fiord, such as the Segue, may be defined as "an arm of theses, which lies in a long, deep valley, With steep punnet or sub-parallel walls, and bee a comparatively even floor, to that the fiord valley is trough-shaped." There is abundant evidence that all fiords are drowned valleys, which have been formed on the land, and which the sea has afterwards entered in consequence of local subsidence. How have these valleys been formed? The generally accepted theory is that they are due to glacial action, having been gouged out of the land by the action of vanished rivers of ice. Pr. Gregory's new "tectonic" theory—already adumbrated by Peschel and Murchison in 1886 and 1870—holds that all true fiords originated as cracks in the hard rocks, due to fractures consequent on the upheaval- of the land by preseme from below. These cracks have since been enlarged by' various denuding agents, among which glaciers played a large part. This theory was first suggested from the resemblance of the plan of many fiord groups to a network of cracks, dividing a former plateau into a series of iselated blocks. Dr. Gregory has established its probability by a great mass of evidence collected from all parts of the world. The three arguments which seem to dispose of the glacial theory are as follows. Fiords and glacial areas do not correspond in distribution. Some fiords—as at Hong Kong—occur where there is no trace of a glacial period. Elsewhere, as in Scotland, the fiords are confined to a single portion of the glaciated area, and that the portion where the ice was least effective. ' Secondly, the shape and arrangement of-the fords are often inconsistent with the established Movements of: the glaciers ; in Scotland, for instance, the ice flowed mainly across the line of the fiords. Thirdly, the geological record shows conclusively that meet fiord valleys are older than the glacial period. To a layman this last argument appeari to.be convincing by itself. But science is based on a meticulous .eiamination of all available evidence, and Dr. Gregory May, we :think, claim to have definitely established the tectonics origin -of fiords in a work which •should remain classic-. on its subject , When a new edition is called for, the anther: may remove the curious slip on page 468, where an argument is based on the rotation of the earth "from east to-west "! Even the most careful scientific. writers nod sometimes.
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