214 



THE CLIMATIC FACTOR AS ILLUSTRATED IN ARID AMERICA. 



Copan was an inhabited city the edge of the 18-foot terrace was washed by the river. 

 To-day floods sometimes reach the foot of the 12-foot terrace, but never rise higher. If 

 the river should again proceed to deepen its channel the present flood-plain would in turn 





-fy.-^- 



;■ 10 



Fig. 73. — Diagrammatic Sections of Wall and 

 Deposits at Copan Ruins. 



A. Oblique section as seen from river. 



B. Cross-section along M-N. 



KEY TO FIGURE 73. 



= Original river deposits on which the ancient town of Copan was built 

 I'pper parts with some clay and fine gravel, but mostly coarse cobbles 

 with small bands of finer gravel. The upper cobble layers are in a 

 matrix of more clayey material and look as if they had been laid down 

 to a depth of 5 to 6 feet, under somewhat unusual conditions, r. g., as 

 if the ordinary course of the river had been interfered with by man. 

 The top of this deposit is about 18 to 19 feet above present low-water 

 level, and 11 to 12 feet above present high-water level. 



= Masonry wall extending down 6 to 7 feet below top of (1), apparently 

 to low-water level of the period when it was built. Otherwise the 

 wall must have been laid in a trench, which is improbable because of 

 the even stratification of (4). 



= Rubble filling, placed inside of wall to form the great mound on which 

 the temple is built. 



= Fine alluvial materials such as fine water-laid gravel and sand mixed 

 with some layers of rounded cobbles and also with layers containing 

 angular bits of limestone, broken cherty flint, and also larger blocks of 

 the limestone of which the walls are made. This looks like a deposit 

 laid down in water just after the wall was built. It hes out.side of (2), 

 just as (2) lies outside of (1) and (3), and it hes on (1) and seems to 

 coalesce with it. Its top is about 4 feet below that of (1). The relative 

 ages of (3) and (4) are not evident. 



= Broken rubble from the ruins up above. It lies outside of (2) and 

 above (4). It is like (3), only more irregular and with less cobble- 

 stones, probably because it fell from the high parts of the wall. 



= About 10 feet of even layers of cobbles laid down by man in a reddish 

 clayey matrix. No significance. 



= Grayish rubble. No significance. 



become a third terrace, but there seems to be no such tendency. It should be added that 

 above the 18-foot terrace are traces of others of much greater age, but these do not con- 

 cern us. 



The facts which have just been stated, and which are illustrated in figures 73 and 74, 

 seem to indicate that the history of the Copan River in relation to the ruins has been approxi- 

 mately as follows: The earliest of the finely carved stelae at Copan bears a date which 

 Morley reads as 251 a.d., but which Bowditch puts about 250 years earlier. The 

 lowest walls of the main temple or citadel must quite surely have been built before the 

 stelae were carved, and it seems safe to say that they probably date back before the time 

 of Christ. Previous to that date the river had built up its flood-plain approximately to 

 the present 18-foot level. At that time, however, it probably was not aggrading its flood- 

 plain to any great extent, for in that case the town would frequently have been flooded. 

 Nevertheless, it may sometimes have overflowed into the town, and to this may be due 

 the somewhat disturbed stratification of the upper part of deposit No. 1 in figure 73, a 

 deposit which lies inside the wall and corre- 

 sponds with the general upper layer of the 18- 

 foot terrace. Even if this is not the case, the 

 river rose quite high, for on the outside of the 

 wall it deposited materials (No. 4 in figure 73) 

 within 4 feet of the level of the main terrace. 

 Next the river cut down its channel to an un- 

 known depth below the 18-foot terrace. Then 

 it built up its flood-plain, perhaps much, per- 

 haps very little, and formed the present 12-foot 

 level. Next it again cut downward, and then once more laid down deposits to form the 

 present flood-plain. 



How markedly the processes of degradation and aggradation were separated we have 

 as yet no knowledge, but on the upper Motagua and in most of the other parts of the world 

 where such terraces are seen the separation is usually distinct. If we assume that the same is 



, H#H^f 



Fig. 74. — Relation of Terraces and Ruins at Copan. 



Numerals indicate approximate height above low-water 

 level. R = River. C = Ruined walls of Copan. 



