The excavation of a sixth-century 
Maya farmhouse at Ceren, in El 
Salvador's Zapotitan Valley, reveals 
a stratigraphic record of volcanic 
activity. The eruption of Ilopango 
in about A. D. 260 buried fertile 
brown soil (A) under a layer of 
white volcanic ash (B). After the 
valley was resettled, a house was 
built with a fired-clay floor and 
clay columns. This structure was 
destroyed by the eruption of nearby 
Laguna Caldera in about a. D. 600. 
Prehistoric remains were unusually 
well preserved under the thick 
deposit of ash from that volcano (C). 
Later eruptions, of San Salvador 
volcano in about 950 and El Playdn 
volcano in 1658, added thinner 
layers of ash on top. 
Onstiar Zier 
house are all associated with female ac- 
tivities. 
The use of both clay and obsidian by 
the fanners at Ceren reminds us that in 
addition to fertile soil there are other 
important resources created through 
volcanic activity. The local clays, 
which the Maya used not only for pot- 
tery and houses but also to build their 
pyramids, is formed from weathered 
deposits of volcanic ash. Obsidian, the 
most valued material for toolmaking, 
is, of course, volcanic glass. Hematite, 
the red iron oxide these people used as a 
pigment, is also a volcanic product. 
After excavating the cornfield, farm- 
house, and outbuilding, we naturally 
wanted to know if there were other, 
similar buried and preserved houses 
and fields. We learned from local infor- 
mants that one such structure, about 
200 feet northeast of our farmhouse, 
was completely destroyed during the 
1976 bulldozing. But how could we de- 
tect buildings under twelve to eighteen 
feet of volcanic ash? With a mixture of 
hope and desperation, I turned to geo- 
physics. In June 1979, with geologist 
Hartmut Spetzler, I tried three portable 
instrument systems in the large field 
south and west of our farmhouse: a seis- 
mograph, a resistivity device to mea- 
sure the passage of the electricity 
through the ground, and ground-pene- 
trating radar. Each was used to try to 
detect buried structures as geophysical 
“anomalies.” Within the 300-by-300- 
foot grid we set up, w'e detected a few 
anomalies to which the resistivity and 
the radar systems were particularly 
sensitive. With the geophysical instru- 
ments alone, however, there was no 
way for us to determine whether these 
anomalies were natural ones caused by 
unusual deposits or conditions of ero- 
sion or (as we hoped) “cultural” ones 
caused by prehistoric Maya structures. 
In January’ 1980, 1 returned to El Sal- 
vador with colleagues from the Univer- 
sity of Colorado to determine the 
nature of the three anomalies. We used 
a core-drilling rig borrowed from the 
geologic department of the Salvadoran 
government. The first anomaly cored 
turned out to be cultural, for the rig 
pulled up flooring at a depth of fourteen 
feet. The second anomaly drilled also 
turned out to be a structure, this time 
buried by twenty feet of tephra. (This 
second anomaly had an air cavity just 
above the floor, something we won’t be 
able to explain until it has been excavat- 
ed.) The third anomaly remains enig- 
matic as no unusual cultural or natural 
feature was detected. We have pretty 
much worked out the technological de- 
tails of locating buried structures; all 
we are awaiting now is the end of the 
civil war that is racking the country, so 
that we can return to excavate more 
buried houses and their fields. 
Given our knowledge of Maya settle- 
ment patterns, we are virtually certain 
that a small city or large town also lies 
entombed somewhere under the Lagu- 
na Caldera tephra, whose maximum 
depths have yet to be probed. Such a 
site should have a pyramid-plaza com- 
plex at its center, with palaces and pos- 
sibly a marketplace and areas for craft 
specialists. The excavation of such a 
site would add immeasurably to our 
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