Growth of Continents. 
503 
It has been a very general belief among geologists that the con¬ 
tinental masses are gradually expanding, or that they grow. 
By erosion the rock materials above the water are transferred 
to the borders of the continental platform, and are there de¬ 
posited in the shallow water and upon the slope. To some ex¬ 
tent deep-seated inland flow may compensate for this. 
However, it has been seen that where great thicknesses of 
sediments are formed, there land areas or even mountain masses 
may subsequently be found, and thus the continents may grow. 1 
No sooner do the land areas rise than erosion begins, and a 
large part of the material is transported seaward and thus still 
farther builds out the continental platform. This statement 
remains true even if in some cases still greater masses of 
material are transported to a mediterranean sea, as may have 
been the case at the time of the deposition of the sediments of 
the Alleghany mountains. The continuation of this process, 
provided no other forces were at work, would finally result in 
extending the continental border at the expense of altitude, for 
wherever the land arises above the sea, that part is cut off and 
transported to the continental border. Finally, if no other 
forces were at work except superficial seaward movement and 
compensatory hypogene flow, they would result in reducing the 
continental platform to the level of the sea and in enlarging its 
borders. And ultimately, as suggested by Gilbert, 2 as a result 
of solution, the entire continental platform would be immersed. 
However, it appears probable that with these forces others are 
at work. 
How vast is the quantity of intruded and extruded rocks has 
already been seen. This material, stopping in the outer part of the 
earth or reaching the surface, becomes a prey to erosion, and like 
the other land materials, and in a similar manner, is distributed 
along the border of the continents, helping in their growth. 
This igneous material comes from far below. Moreover, there is 
no reason to believe that during the periods of regional vulcanism 
the volcanic regions subside an amount equivalent to the intrusions 
1 J. D. Dana: Phil. Mag., Vol. 46,1873, p. 49. 
3 Continental problems, by G..K. Gilbert: Bull. Geol. Soc. Am., Vol. 4, 
93, p.18 9. 
