Overview
The Emeryville Shellmound was an archaeological deposit so
massive that it resembled a small hill resting on the shore of the
bay. How did this hill come to be formed and what happened to it?
An archaeological deposit such as the Emeryville Shellmound
can be envisioned as a "slice" of time. Over time, an archaeological deposit builds up, layer on layer. The
bottom layer--or base of the deposit--represents the earliest occupation. Successive
layers, or strata, deposited on the strata below represent later and later periods of
occupation, like steps up through time. Human activity or environmental
events that take place after the strata are deposited may disturb or remove some of the strata, but a portion
of the basic stratigraphy--arrangement of successive layers--still
may
be preserved. This was the case at Emeryville. Although most of the site was destroyed in the 1920s, the
preserved basal strata of the mound were a valuable archaeological resource.
The Emeryville Shellmound was deposited over a long period
of time, starting about 2800 years ago. About 5000 years ago, extensive marshes developed around the
shore of the San Francisco Bay. This ecozone offered an extremely rich habitat for a
wide range of plants and animals. The bay itself provided travel and trade routes, as well as
a seemingly endless supply of fish, sea mammals, waterfowl and shellfish.
The native people of the region began increasingly to settle on the bayshore to take advantage of
these rich resources. At Emeryville, where Temescal Creek entered the bay, the
meanderings of the creek deposited "dikes" of silt and gravel, which provided camping
areas slightly elevated above the marsh level. The creek itself provided what was
probably a year-round source of fresh water, while the bay, its marshes,
and the surrounding oak woodland supplied ample sources of food and tool materials.
Most abundant of all resources, perhaps, were
shellfish. Although the margins of the bay offered a wide variety of
species, most common, and extremely abundant, were mussels and oysters and, somewhat later in time, clams. All of
these could be harvested in quantity along the bayshore. Shellfish could be prepared easily for immediate
consumption or even eaten raw, and also could be dried and stored. However, significant
quantities of shell would be discarded in a relatively short time, by even a small group of
people harvesting and dining regularly at a settled spot. For example,
20 people each consuming (a conservative) 10 oysters a day would discard
12,000 shells in a month,
or 144,000 shells in a year. Add to this the charcoal and ash from cooking fires,
waste from the butchering of animals and cleaning of fish, and rocks and plant matter imported
for building or tool use and eventually discarded: altogether this would represent a
substantial accumulation of soil from the occupation of a small
group of people. Archaeologists call this material shell midden. In the
areas people used most often or where they camped or settled along the bayshore,
midden accumulated in layers and began to form mounds. Some 400 such mounds were
recorded by an archaeologist who surveyed the shores of San Francisco Bay area in 1902
(Nelson 1906). The Emeryville Shellmound was exceptionally large: at its maximum, the
mound was as much as 40 feet high and at least 350 feet in diameter.
The site that was to become the Emeryville Shellmound
probably was first settled about 800 BC. By 250 BC, the settlement at Emeryville had deposited a substantial pile of
material, which rose gradually from the bayshore in a gently sloping mound. Although
the cultural deposit was as much as eight feet thick by this time, the mound's elevation
from the surface would not have been perceived as eight feet high.
While the mound was accumulating, the
lowlands around the base of the mound continued to build up as well, not only with a widespread thinner
deposit of cultural debris, but with the accumulation of sediments from the bay
and from Temescal Creek, and decayed organic material from the adjacent marsh and woodlands.
The mound was a "living" part of the continuously changing landscape. The growing
mound afforded both a view of the bay and the surrounding shore, and also a dry living
area elevated above the tidal marsh at its base. Fire hearths and storage pits were built
and graves excavated in the soft soil of the mound. By this time, if
not long before, people were living year round at the site. Meanwhile, the mound continued to grow, with
the continuous deposition of shellfish and other organic debris.
Sometime during the period between 250 BC and 0
AD, the mound began to slope more steeply, so that eventually the
deposit would take on the form of a steep-sided cone. Possible this steep "growth" of the mound represents
intentional building of the deposit. As the mound grew more steeply, each newly deposited "layer" in effect was draped
over the top and down the sides of the mound, and spread out into the surrounding plain.
Archaeological dating shows that the deposit forming the "arms" of the mound continued
to grow southeastward for at least another 1000 years, as the mound also grew higher.
Archaeologists believe that the use of the Emeryville
Shellmound proper ended around 700 years ago. This is speculative, because the upper structure of the cone, which
would represent these later periods, was destroyed in 1924.
Radiocarbon dating, which could have
provided a fixed date of abandonment had not been invented. However, many other sites around the bay were
abandoned around this time. It is possible that long period of drought forced people to move
away from the bayshore and closer to the sources of creeks, to ensure a supply of fresh
water.
At one time there were several other shellmounds near the
mouth of Temescal Creek. One very large mound was located a few hundred yards east of the Emeryville cone.
Because none of these deposits was investigated before they all were
destroyed during the late 1800s, we know almost nothing about when they were deposited or how they
were used. However, archaeological investigations in 1999 revealed the
presence of another previously unrecorded shellmound a few hundred feet southwest of the former
location of the big cone. This much smaller mound probably was first
occupied after people
stopped using the big mound. People lived there for a few hundred
years ending sometime shortly before the arrival of the Spanish in the Bay
Area.
At the time of the 1999 archaeological investigations of the
Emeryville Shellmound site, the archaeological material deposited around
250 AD to 0 AD was exposed at the modern
surface level. Most evidence of the layers above, that had formed the cone of the Emeryville Shellmound
and that represented the period between about 250 AD and 1300 AD, had been graded away
when the site was leveled for development in 1924.
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