262 



University of Califcvnia. 



LVOL. 2. 



insignificant, a little more than 100 feet at San Carlos probably 

 being the maximum. The plains were tilted toward the seas on 

 both sides of the Cordillera de Veraguas, and from the angles at 

 which they slope it is probable that along the axis of the 

 cordilleran region, the land rose as much as several thousand feet. 

 In traversing that region, even before recognizing the significance 

 of the tilted plains, I was satisfied that the sierra had suffered a 

 considerable uplift in comparatively recent times. I now know that 

 the whole region has been bowed. Some of this arching may be 

 due to a recent movement perhaps not yet ended, but a considerable 

 part dates from this Middle Pleistocene disturbance. 



On the western side of the Peninsula of Azuero, south of the 

 tilted Mariato coastal plain, the Pleistocene peneplain was developed 

 on hard formations, but it has been uplifted and cafioned by the 

 streams. It rises inland at such a rate as to indicate that the 

 central line or mountain axis of the peninsula has risen since 

 Middle Pleistocene time as much as 1,000 or more feet. 



A KECENT DEPRESSION OF THE COASTAL LANDS. 



The outline of the Isthmus of Panama is that of a land whose 

 borders have recently subsided and been partially submerged. 

 Especially is this true of the Pacific side. West of the Peninsula 

 of Azuero are several beautiful examples of drowned valleys. That 

 of Montijo begins far inland as a common river valley of the canon 

 type, and an age subsequent to the uplift of the Pleistocene pene- 

 plain. As it proceeds southward it opens up into a broad topo- 

 graphic depression partly of structural and partly of erosive origin. 

 Tide water ascends in this to 40 miles from the open ocean, and 

 the body of water gradually widens until it is several miles in width 

 and has become the so-called Gulf of Montijo, partly closed in from 

 the open sea by several large islands. The "gulf" is shallow and 

 in its upper portion great mud-fiats are exposed at low tide. 

 Evidently the depression which admitted the sea into the old valley 

 had a very small amplitude. 



Around the extremity of the Peninsula of Azuero, the evidences 

 of a recent subsidence are very clear. It always seems that the 

 depression has been most on the ends of long headlands and relatively 



