MICHIGAN ACADEMY OF SCIENCE. 9.9 



ORIGIN OF CONTINENTAL FORMS, V. 



HOWARD B. BAKER. 



One of the most important objections to the theory of the post-Cre- 

 taceous separation of mass from the earth as I have developed it in preced- 

 ing papers before this section, is based upon the relative values of the coastal 

 margins of the continents and the submerged continental borders. 



Fisher, 1882, referred only to the very broadest geographical features and 

 did not concern himself with the submarine border. Pickering, 1907, also 

 used very general features, but he supposed that comparisons must deal 

 with the submerged continental margins. In contrast with their methods, 

 I have not only compared continental margins in considerable detail, but 

 my whole development of the theory is built up primarily upon the form of 

 coastal margins as actually represented upon the globe. 



Against this method the criticism arises that the position of the strand is 

 not a permanent feature, that it is ever varying. Very slight crustal move- 

 ments must suffice greatly to change the outlines of land and sea. Both 

 erosion and sedimentation are constantly at work; it would seem to many 

 that nothing is more unstable or less reliable, for such a purpose, than the 

 fleeting picture which the map presents of the present-day relations of land 

 and sea. As contrasted with the strand line, the submarine margin of the 

 continental plateau is held to be the real margin. The ocean basins, so 

 called, are said to be slightly over-full. The hundred fathom contour is 

 regarded as about the brink of the real oceanic depressions of the globe. 



It is objected that any comparisons of opposite coasts, which may or may 

 not match each other's curves, must be made on the basis of this real con- 

 tinental margin and that coastal evidence must be thrown out as inadmissible. 

 What is there to ])e said in reply? 



The first point to be made in reply is that this objection gives preference 

 to the a priori method over the analytical. To investigate coastal curves as 

 actually charted is to study at first hand facts which are as much beyond 

 denial as those connected with the submerged margin. If opposite coasts 

 match together that geological fact demands explanation and is not to be 

 brushed aside merely because in the light of previous conclusions the reason 

 for the fact is not at once apparent. And, I may add, it is no more proper 

 to attribute coastal parallelisms to chance than to assign to slaty cleavage 

 or rock stratification the same fickle origin. And yet, are there not even 

 today and even in the ranks of geologists a few who attempt in some such 

 way to remove from discussion the, to them, unwelcome fact that coasts are 

 fractured margins and the fractures fit together? 



We might suppose that the hundred fathom contour or some other would 

 be more reliable for times as remote as the end of the Mesozoic than the 

 zero contour which is the strand, but can that be proved? Quite the con- 

 trary. 



The second point is that the proper use of the coast lines necessarily makes 

 provision for the submerged areas. 



The coasts are not straight, they are made up of curves, and when we 

 place them parallel with each other the major curves are concentric. It is 

 very noticeable that the coastal curves are not parallel, i. e., concentric, 



