HILL: GEOLOGY OF THE ISTHMUS OF PANAMA. 



203 



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Panama Bay. 



Although we have now passed from the Caribbean to the Pacific, the 

 continental section is not yet completed, for its features continue south- 

 ward, twice as far, across the waters and islands of the 

 Gulf of Panama. This great pouch-like indentation 

 into the southern coast of the Isthmus of 

 Panama, 100 miles long, is exceedingly 

 shallow, hardly reaching 50 fathoms in 

 depth until we cross an imaginary line 

 drawn between the opposing headlands 

 marking the entrance to the Gulf. (See 

 Plate VI.) Beyond this line, which is 

 a continuation of the shores of the most 

 southerly mainland bordering the Pa- 

 ^ cific, the submarine profile makes a sud- 



den plunge of from 50 to 1,800 fathoms 

 or more. Thus it will be seen that the 

 bottom of the Gulf of Panama is really 

 but a few feet below the present level 

 of the sea, and a slight elevation would 

 convert the whole bay into a rugged 

 land area similar to that of the present 

 mainland. 



Furthermore, this great gulf is marked 

 by numerous islands and islets rising 

 above this submarine platform of the 

 bay. Some of the summits rise higher 

 than that of Culebra, the so called con- 

 tinental backbone. The highest of the 

 eleven pointed hills of Tobago Island is 

 o-j a nearly a thousand feet in altitude (ex- 

 !m . '*7 actly 935 feet), while the adjacent To- 

 baguilla is 710 feet. 



The intervening floor of the bay be- 

 tween these islands and the mainland, 

 only a few miles distant, is but seven fathoms (42 feet) 

 in depth. Still farther out into the bay the group con- 

 stituting the Pearl Islands present the same rugged Panamic topog- 

 raphy, the points rising to various altitudes, some of them as high as 

 600 feet. 



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