26 
FIFTEENTH REPORT. 
ORIGIN OF CONTINENTAL FORMS. IT. 
DISCUSSION OF MR. TAYLOR’S THEORY. 
There are at least live main theories of the origin of continental 
forms : 
1. Unequal radial contraction of a cooling earth. 
2. Prof. Chamberlin's theory of the leaching out of basic materials 
from exposed land and their deposition in the sea. 
•“>. Prof. Sness’ theory of the foundering of portions of the earth's 
crust into the interior of the planet. 
4. Mr. Taylor's theory of crustal creep. 
5. The theory of the terrestrial loss of mass, developed from the sug- 
gestions of Rev. Osmund Fisher, which I have heretofore presented in 
outline before this section. 
There are certain leading facts which any satisfactory theory must 
take into consideration. For example the following: 
1. The present forms of the continents and the low density of their 
materials. 
2. That the margins of the continents exhibit fracture. 
3. That many of the fractured borders may be matched together so 
as to produce a consistent pattern. 
4. That when they are so matched together the surface geology in 
several significant places also forms a consistent pattern. 
5. That the Pacific border structures are set in a radial or rotating 
arrangement. 
(>. That the Atlantic fractures date from the end of Mesozoic time. 
These facts I hold to be fatal to the first three theories mentioned, viz. : 
contraction, leaching and foundering, and. for the present, their dis- 
cussion will be postponed in order to take up the theory of crustal creep. 
Not that unequal contraction and leaching are wholly excluded as pos- 
sible factors, but they have not been dominant factors. 
Tn 1908. Mr. F. B. Taylor presented in abstract before the Geological 
Society of America a paper on the “Bearing of the Tertiary Mountain 
Belt on the Origin of the Earth's Plan.” It was published in full in 
the bulletin of the society in 1910. Briefly summarized, this paper pre- 
sents the theory that during Tertiary time, possibly in part earlier, 
the continental sheets of North and South America, Eurasia and 
Australia experienced slow lateral motion which Mr. Taylor calls 
“crustal creep.” This movement resulted in mountain building along 
the anterior borders of the moving sheets, thus explaining the peculiar 
distribution of the Tertiary mountains. North America is thought to 
have moved southwest away from Greenland, Eurasia, southeast from 
Greenland but for the most part south, South America mainly north- 
west, and Australia northeast. Africa is thought to have moved east- 
ward but only slight folding and slight elevation toward the eastward 
are cited. The author believes in crustal creep away from both poles, 
and is inclined to look for the explanation in some form of tidal force. 
