14 THE AUSTRALIAN NATURALIST, 
' GEOGRAPHICAL CHANGES IN GEOLOGICAL 
TIME. R 
By H. I, Jensen, B.Sc. 
To whatsoever branch of natural history we devote our atten- 
tion, we see cycle on cycle set. Repetition of similar events 
at intervals occurs as truly in natural history asin human 
history ; as examples of such repetitions one might quote sun- 
spot periodicity, weather cycles or magnetic cycles, as well as 
the whole progress of organic life and evolution. Nature, 
indeed, is a vast recurring decimal. The ancient Brahmins 
described the evolutions of the earth froma mass of atoms to 
an organic whole, and believed that it would be resolved again 
into atoms at the end of a “ Kalpa” to commence the process 
afresh. This alternate creation and destruction tended in their - 
minds to hinder stagnation and to beautify by effect of contrast. 
Kternal change is also a characteristic of the features of 
which we geologists make a study. The earth is continually 
being altered in aspect, and places once dry land are now 
deeply submerged, while other areas have been reclaimed from 
the sea by geological processes. One region in which such 
changes have been effected in the historic period is the north- 
west of Europe. We know how the sea has captured part of 
Holland and how it is continually encroaching on southern 
Scandinavia and Denmark. Many flourishing farms of 600 
years ago are now beneath the Baltic wave. As Héédt writes: — 
; Where the sea is smiling 
So peacefully, 
There stood a city 
In days gone by ; 
But the green earth opened 
To make a grave, 
And the city slumbers beneath the wave ! 
or Klaus Groth— 
Under the sea lies Biisum old, 
O’er it the waters wild have rolled ! 
While Denmark and Skaane are thus subsiding Sweden, north 
of Skaane, and Norway are undergoing elevation, nevertheless 
the fiords of Norway, which are considered to be drowned 
valleys, show that this part has lately emerged from an age of 
subsidence. 
We may forthe purpose of this study classify earth move- 
ments into (a) Great movements of continent making and 
mountain building depending on folding, (b) Sudden and less - 
important movements of subsidence effected by means of fault- 
ing probably induced by volcanic extravasation, (c) Small 
crustal movements along the coasts depending on changes in 
load brought about by the denudation of the land and the 
accumulation of sediments in the sea. 
