1911 Encyclopædia Britannica/Fjord

From Wikisource
Jump to navigation Jump to search

FJORD, or Fiord, the anglicized Norwegian word for a long narrow arm of the sea running far inland, with more or less precipitous cliffs on each side. These “sea-lochs,” as they are sometimes called, present many peculiar features. They differ entirely from an estuary in the fact that they are bounded seawards by a rocky sill, covered by shallow water, and they deepen inland for some distance before the bottom again curves up to the surface. They are thus true rock basins drowned in sea-water. It is pointed out by Dr H. R. Mill that Loch Morar on the west coast of Scotland, a fresh-water basin 178 fathoms deep, with its surface 30 ft. above sea-level, which is connected with the sea by a short river, is exactly similar in configuration to Loch Etive, 80 fathoms deep, filled with sea-water which pours over the seaward sill in a waterfall with the retreating tide; that Loch Nevis with a depth of 70 fathoms has its sill 8 fathoms below the surface, while the gigantic Sogne Fjord in Norway, more than 100 m. in length, is a rock basin with a maximum depth of 700 fathoms. Any inland rock basin such as Loch Morar would become a fjord if the seaward portion sank below sea-level. The origin of these rock basins has not yet been satisfactorily determined. Recent work upon somewhat similar basins in the high Alps has suggested local weathering of surface rock in fracture belts or faulted areas, or dikes, where material is easily eroded, thus producing a trough bounded by high walls in which a lake forms under favourable conditions. But investigations in such regions as the Rocky Mountains and the Yosemite Valley, where there is frequently a “reversed grade” similar to that near the seaward end of rock basins and fjords, seem to show, in some cases at least, that such a formation may be due to the “gouging” effect of a glacier coming down the valley which it constantly deepens where the ice pressure and the supply of eroding material are greatest. There may be several causes, but the results are the same in all these drowned valleys. The mass of sea-water in the depth of the basin is either unaffected by the seasonal changes in surface temperature, which in Norway penetrate no deeper than 200 fathoms, or else, as in Loch Goil, the fresher film of surface water responds quickly to seasonal changes, while the heat of advancing summer penetrates so slowly to the depth of the basin that it takes six months to reach the bottom, arriving there in winter. It has been found that where the fresher surface water has been frozen over, the temperature may be as much as 45° F. at a few fathoms from the surface. When the surface is warmest, on the other hand, the depths are coldest.