261 Wisconsin Academy of Sciences, Arts, and Letters. 
Physical Features of Lakes. 
LAKE AMATITLAN. 
Lake Amatitlan is situated in 90° 30' west longitude and 
14° 25' north latitude. By rail it is 29.6 km. (18.5 mi.) from 
Guatemala City and 89.6 km. (56 mi.) from San Jose, the most 
important seaport of the republic of Guatemala on the Pacific 
coast. Its surface is about 1180 m. (3870 ft.) above sea level and 
some of the neighboring mountains rise to an elevation of 250 m. 
to 400 m. or more above the lake, thus giving the body of water 
the general characteristics of a typical mountain lake. A short 
distance southwest of the lake is the volcanic peak Pacaya, which 
reaches an altitude of about 2550 m. while to the south lies an¬ 
other volcano known as Aqua, whose altitude is given by some 
authorities as 3750 m. and by others as 4100 m. To the north¬ 
west of the lake the mountains consist of hard granitic rock but 
all of the others in this vicinity are composed largely of loose 
material, such as volcanic ash and pumice which are easily 
eroded. 
The depression occupied by the lake owes its existence to the 
forces which produced the surrounding mountains, but the dam 
which impounds the waters was produced in part, perhaps, by 
volcanic agencies. 
Along the greater portion of the lake the shore is rugged and 
possesses a steep slope, but about half of the north shore con¬ 
sists of a fairly broad, low plain which has been built by the 
Lobos river and the temporary streams which enter the lake 
from the north. (See fig. 1, p. 217.) The higher land back of 
this plain is composed of material which is easily eroded so that 
the waters coming from this region carry a large amount of 
debris. Even during the height of the dry season the Lobos 
river brings down a. fairly large amount of this material which 
is deposited at the mouth as a typical delta formation. This 
plain is an excellent example of the encroachment of land on a 
lake. Apparently more than a third of the original area of the 
lake is now occupied by this plain, which is about 6 km. long by 
about 2 km. wide. 
The lake is long and narrow, with its main axis extending al¬ 
most east and west, being slightly inclined to the northwest and 
