Topic 1:
Earthlodges in the West Pasture

In the West Pasture, we have found quite a few prehistoric pithouses that date to the Plains Village period. The three pithouses that have been investigated most thoroughly are named for characters in the Hank the Cowdog books---Hank’s House (41RB109), Drover’s­­ House (41RB108), and Pete’s House (41RB108). Two of these houses—Hank’s and Drover’s—both burned down, while Pete’s House did not burn and was left to slowly disintegrate through natural processes. The contrast between the unburned pithouse and the burned pithouses could not be more striking.

At Pete’s house, the floor and walls of the structure were difficult to recognize, and the central fire pit was the only house feature that was well preserved. Hank’s and Drover’s Houses, on the other hand, were burned down at or near the end of their useful lifespans, and the burning may have been intentional to remove the old houses. The burning episodes preserved many of the materials used in the construction of these houses, allowing us to see architectural details that are normally not preserved. It was these architectural details---preserved in the form of burned earth, fired clay, and charred wood and grass---that allowed us to recognize that Hank’s and Drover’s houses were Plains-style earth lodges.

There is a saying in archeology that “the house is the artifact.” What this simply means is that you can think of a house as one big, complex artifact. One must study all of the various parts of the house in order to understand the whole house. In the case of prehistoric houses, we study the parts to enable us to reconstruct the whole house. In a sense, Hank’s and Drover’s Houses became complex artifacts the moment that they burned.

Radiocarbon dates (2-sigma calibrated) on charred organic materials show that Hank’s and Drover’s Houses date to the Plains Village period:

Hank’s House

The controlled excavations of these burned structures uncovered large amounts of charred wood, fired daub (also called burned daub), and thermally altered sediment. Daub is the fine-grained clay that was mixed with water (and sometimes grass) so it could be molded while in a plastic state. Daub was applied to the wooden elements that comprise the walls and roof framework of the houses, and it became hard when it dried. When the house burned, the daub was intensively heated to a ceramic-like state. Archeologically, the firing of the daub is what all makes it durable so that it is preserved.

During the excavations of Hank’s and Drover’s Houses, ALL the fired daub was collected for later study. The daub from Drover’s House has been carefully and systematically analyzed. During this study, it became apparent that there were essentially two types of daub used to build the house:

1.    Natural daub—raw clay

2.    Fabric daub—raw clay with fine grass mixed in

This initial application of mud placed on the timber roof framework consisted of a mix of fragments of fine grass added to a fine-grained clayey sediment. The grass was added to the clay to strengthen it, much like rock or shell fragments are added to temper clay for making pottery. When the house burned and the daub got fired, the grass pieces vaporized, leaving tiny hollow tubes where each blade of grass had been. The consistent presence of randomly oriented hollow tubes is unmistakable evidence of intentional preparation of a strong bonding materials that we call fabric daub.

A classic specimen of “fabric daub” characterized by linear impressions and circular tubes with tiny inclusions of burned-out grass. These impressions are visible throughout the daub interior and on the exterior surface, indicating that fabric daub was an intentional mixture of grass and clay, with the clay strengthening the daub when it dried (scale in centimeters).

The intense of burning event that destroyed Drover’s house around 700 years ago preserved critical evidence related to the superstructure. Details of the architecture that would not normally be seen were beautifully preserved. During the archeological excavations, we were able to record these details in great detail. By studying the field evidence in conjunction with the lab analysis of collected specimens of fired daub, we were able reconstruct the house design using a relatively simple principle called “reverse engineering.” The investigation was, in effect, an exercise in taking apart the burned house, piece by piece through careful excavations, to determine how it was originally constructed. The superstructure, including the walls and roof constructed over the house pit, was composed of wood logs and branches, grass, mud mixed with grass, and earth. But the evidence of the superstructure was more complex than we ever expected.

Certain specimens of burned daub became our “keystones” for determining how the superstructure was designed. Some of these specimens led us to the discovery of an interior decked platform constructed in the center of the house and supported by the four central support posts. This architectural feature had never been identified before in a Plains Village house. Also, the evidence led us to realize that the house builders intentionally split cedar and juniper branches into planks that averaged 5.2 cm (2 inches) wide and at least 2.7 cm (1 inch) thick. This was a profound discovery that was totally unexpected. These split-branch planks were positioned horizontally across 3.3-inch-diameter (8.5 cm) cross-stringers and spanned a rectangular opening that measured  3.5 x 2.5 m (8.9 x 8.2 feet). This created a horizontal deck “platform” in the center of the house, and it had a circular opening in its center that served as the smoke hole directly over the central hearth. This platform framework was covered with 3.4 cm (1.75 inches) of fabric daub, with more dirt (natural daub) added above it.

Platform decking daub with parallel plank impressions (50-cm scale with 10-cm increments; Lot 95 daub).

The remainder of the roof beyond the deck platform was also covered with a moist grass-mud mix forming a plaster layer averaging 1.9 cm thick (¾ of an inch) thick. This fabric daub was placed on a wattle framework spanning the rafters. The wattle framework consisted of smaller branches averaging 2.8 cm (1 inch) in diameter and spaced an average of 2.8 cm (1 inch) apart, with additional layer of similar sized branches running perpendicular above, thus creating a web of upper and lower branches. In addition, small split branches were also incorporated into these layers of interior roof wattle.

Slightly larger branches were used to span across the roof rafters and then a second layer of branches was placed perpendicular were plastered with grass-filled mud that fired to become fabric daub. This view is looking upward from inside the house (10-cm scale with 1-cm increments; Lot 352 daub).

The archeological evidence shows that the roof of Drover’s House had a primary framework of rafters that radiated outward from the central platform, and each rafter post extended from the platform past the vertical walls and onto the ground surface. Fired daub impressions provided the dimension of at least one rafter post. This specimen had an impression of a 17-cm-diameter (6.7-inch) rafter beam that supported smaller cross-stringers that formed a wattle-and-daub layer.

This fired daub specimen has a 17 cm (6.7-inch) diameter rafter impression with impressions of wattle cross-members (smaller branches) above (5-cm scale with 1-cm increments; Lot 352 daub).

Placing the daub impression upon a cedar posts provides visual clarity showing the large size of the roof rafters. The large post on the left is 17 cm (6.7 inches) in maximum diameter (Lot 352 daub).

During the excavation of Drover’s House, large specimens of natural daub were found above the timber-impressed fabric daub. This consolidated burned sediment covered the entire roof.

Large natural daub specimens representing roof-fill above the timber impressed fabric daub (scales at left and center have 10-cm increments; Lot 258 daub).

Many specimens of natural daub exhibited robust stem and leaf impressions of grass that had been placed between two layers of earthen material—above the cured fabric daub and under the earthen roof-fill (loose dirt placed on top). Adding this layer of grass would have anchored and strengthened the roof, but it also served to wick any moisture that might penetrate through the upper layer of loose earth.

Remnant of charred grass encased in burned sediment, found stratigraphically above the fabric daub layer. This represents a layer of grass between the intensively fired fabric daub below and the less intensively heated natural daub above (scale is 10 cm with 1-cm increments).