WOODWORTH: GEOLOGICAL EXPEDITION TO BRAZIL AND CHILE. 99 
of decomposed rock may be observed to a depth of over 100 feet, the 
surface of the still solid rock underneath presents ridges and hollows, 
succeeding each other according to varying durability under thé 
influence of percolating carbonated water. In this kind of weathering, 
where erosion does not come into play, it is evident that the resulting 
topography must, in some important respects, differ from that of an 
ordinary surface of superficial denudation. In particular, rock basins 
may be gradually eaten out of the solid rock. These will remain full 
of the decomposed material, but any subsequent action, such as that 
of glacier ice, which could scoop out the detritus, would leave the 
basins and their intervening ridges exposed.” 
VII. GEQMORPHOLOGY OF SOUTH BRAZIL. 
In the preceding chapters so much has been stated concerning the 
form and relief of the tableland of south Brazil, in describing the 
structure and position of the Permian glacial beds, that little remains 
in treating specifically a sketch of the geomorphology of the region 
than to summarize the matter in more systematic terms with the 
added enumeration of certain details. 
Regarded as a land form south Brazil is an elevated tableland with 
a short steep slope descending to and below the Atlantic sea-level and 
a long gentle slope towards the interior of the continent. The surface 
of this warped mass appears to have been in Cretaceous times much 
more nearly a plane. Since its elevation and warping it has been 
dissected by streams which have etched out the structure of the 
westward dipping beds of the long westward slope into lines of escarp- 
ments formed of the edges of the harder more resistent beds over- 
looking lowlands. 
For convenience of treatment the region may be divided into two 
districts which by their geological nature and relief at once impress 
_ the visitor to Brazil. First, the steep coastal border of the Serra do 
Mar, and second, the tableland or planalto proper. 
The Serra do Mar, notched and pinnacled in the states of Rio de 
Janeiro and Sao Paulo, declines to the southward, and in Santa Catha- 
rina retains more of the character of the warped surface of mature 
relief which appears to have been characteristic of the whole belt in 
an early stage of its development following the warping above noted. 
In eastern Parana the summits of the Serra do Mar form a line of 
peaks and ridges rising well above the eastern portion of the tableland 
