tay INSTITUTE OF SOCIAL ANTHROPOLOGY—PUBLICATION NO. 4 
SOIL TYPES 
Soils in the Lowlands (costa) below about 700 m. are 
predominantly alluvial. In the outer Lowlands, or Coastal 
Plain, from sea level to 100 m. (328 ft.), there is a heavy 
black silty soil, swampy in the rainy season, then dried and 
cracked in rough, irregular blocks during the rest of the 
year. Above this region there are loams, varying in color 
from buff to mahogany brown. Reddish loams over pumi- 
ceous, ashy subsoils characterize the boca costa, or piedmont, 
marginal to the inner edge of the Coastal Plain, with which 
it blends imperceptibly. Highland soils are loamy, with more 
clay than in the Lowlands, yellowish to dark brown in the 
young volcanic region, often reddish in leached and eroded 
sections of the older volcanic and nonvolcanic areas. Severe 
gullying is widespread, especially in the sheep-grazing regions 
of the Highlands. Near Momostenango and Quiché it is 
particularly evident (pls. 29, c; 30, e, f). Raw humus is 
deep and well developed in the high, undulant alpine mead- 
ows, especially above about 2,500 m. (8,202 ft.) (pl. 32, a, b). 
NATURAL VEGETATION 
(Map 7) 
The vegetation pattern fits roughly into the climatic and 
edaphic scheme. Along the littoral back from the high, bare, 
barrier beaches is a low, dense thicket dominated in places by 
swamps of mangrove and fan palms. Most of the Coastal 
Plain, however, is covered with savanna grasses and open 
stands of tall, spreading trees, having a somewhat deciduous 
character (pl. 3, c, d). Gallery forests line the numerous 
streams which flow across the plain. Dense groves of 
giant corozo palms are common in the outer Lowlands 
(pl. 2, a). There is a great diversity of useful plants, culti- 
vated and uncultivated, throughout the coastal Lowlands, the 
open, parklike aspect of which is in part a result of climate 
and in part, of oft-repeated clearing for agriculture. The 
belt of heavy orographic rains, along the lower Pacific moun- 
tain slopes, is covered with a natural vegetation of luxuriant, 
wet monsoon forest (pl. 5, b, c; maps 6,7). Much of this 
has been replaced by artificial plantings, especially along the 
interfluvial ridges, of coffee and shade trees. Upward from 
about 1,500 m., where annual rainfall is generally reduced, 
more open forest prevails, with evergreen oaks and long- 
leaved pines in abundance, the latter appearing especially 
above 1,800 m. along the Pacific versant (pls. 10, a; 12, d; 
28). A giant, coarse bunchgrass (Muhlenbergia sp.) becomes 
dominant in the vegetation picture, along with pines, in the 
elevated realms (above 2,500 m. or 8,202 ft.), while the 
rounded summits are crowned (above 3,000 m. or 9,842 ft.) 
with flower-carpeted alpine meadows, shaded occasionally by’ 
thin stands of cypress and giant pines, and draped, during 
the day, with billowing mountain fog (pls. 30, a; 32). The 
desiccated interior troughs and basins of Southwest Guate- 
mala are covered with xerophytic associations, dominated 
by cactuses and thorny acacias and mimosas (pls. 42, e; 
43, e. 
REGIONS OF SPECIAL EMPHASIS IN THE 
FIELD WORK 
(Map 4) 
Lake Atitlan region (map 20).—The Lake Atitlan 
Basin is a huge, oval-shaped, volcanic depression (caldera) 
which has resulted apparently from a crustal collapse fol- 
lowing long-continued outpourings of ash and lava. The 
average diameter of the caldera is about 15 miles (24 km.). 
Precipitous gullied walls, gorges, and headlands border the 
crescentic Lake (mean elevation 5,100 ft. or 1,554 m.; maxi- 
mum depth 1,083 ft. or 330 m.) on three sides (pls. 45, 46), 
the south shore being formed by volcanic cones (three major 
and four minor ones) which have risen from the old caldera 
floor and rim, and which have apparently elevated the level 
of the water somewhat by blocking the normal drainage 
toward the Pacific. Because of the rugged surroundings and 
rough water, most of the 13 well-nucleated Lake-shore settle- 
ments are sharply isolated from one another. The Lake 
drainage is now entirely subterranean, the greater flow prob- 
ably being from under the southeastern corner. There are 
long-term periodic fluctuations in level which seem to be due 
to shiftings of deep-seated fissures, variously opening and 
closing outlets. I observed water moving toward one of 
these outlets near San Lucas in 1936 (see map 20). (What 
is probably this same outlet, and another near San Antonio, 
are indicated on the 1685 (?) map of Fuentes y Guzman, 
1932-33, vol. 2, opposite p. 60.) A subordinate factor is seen 
in alternations of abnormally wet and dry years. A hypo- 
thetical physiographic and probable historical sequence of 
levels, based upon field and library evidences, follows. 
In the early history of the Atitlan Basin the water line 
was much higher than at present, perhaps between 5,700 feet 
(1,737 m.) and 6,000 feet (1,830 m.) elevations, with surface 
drainage, mainly, if not solely, at the present bay of San 
Lucas (pl. 46, d). Erosion may have cut down the south- 
eastern arm, dropping the Lake far below its present level, 
so that the Rio Panajachel and Rio Quixcap, entering the 
basin from the north, cut deep canyons. As Volcano Atitlan 
grew, it raised the southeastern Lake rim, and hence the 
water level, to about 5,200 feet (1,585 m.). Then the 
northern river valleys were flooded, so that fine-grained 
deltaic deposits resulted. At the time of the Conquest, the 
Lake level was about 30 feet lower than at present (5,080 ft. 
or 1,548 m., 1936), then by the late 17th century it was about 
20 feet higher (5,100 ft. or 1,554 m.), where it still appeared 
to be early in the 19th century. In about 1824 it had fallen 
40 feet or 12 m. (to 5,062 ft. or 1,543 m.) ; rerisen to 5,100 
feet by 1866; dropped to 5,080 feet (1,548 m.) between 1900 
and 1910; reached 5,062 feet about 1920, until it began to rise 
once more in 1930 (pl. 18, b). The greatest known increase 
of any one year was 11 feet, in 1933, which was phenomen- 
ally rainy. The rise continued until 1936, when outlets ~ 
appeared to maintain it at about 5,080 ft. (pl. 18, d). An 
average annual rise and fall, with wet and dry seasons, is 
approximately 314 feet. As an historical average, and for 
convenience, 5,100 feet has been assumed as the Lake level 
for map 20 (pl. 47). Rich in micro-organic life, the Lake 
teems with fish, especially very small ones, of which there 
are three main species, one of them important for food. 
Larger fish (mojarras), though numerous, are seldom taken, 
