Deep Gradient/Suspect Terrain
Yerba Buena Gardens, San Francisco, CA, 1993

Deep Gradient/Suspect Terrain is comprised of a 20’ tall, deep green, ship-like structure constructed of painted steel and glass sitting at a steep angle in the East Garden area of Yerba Buena Gardens. Two 12" in diameter glass view ports set flush with the paving on the western side of the Visual Arts Center complete the project. Sealed within the ship on each of its ribs and along its bottom are deposits of continental shelf sediment gathered from beneath the ocean 4 miles off the coast of San Francisco. A misting system for water along the keel side of the interior is activated several times a day. The mist was designed to actuate natural condensation and promote an inner climate of light rain and eroding silt. Incidental plant growth occurring within the ship is a product of seeds naturally deposited in the sediment and nurtured by the greenhouse conditions within the ship. This interior volume is intended as an experimental space where condensation, erosion, sedimentation, growth and decay are allowed to proceed undisturbed according to the climate and interaction of the entrained elements.

The project refers to the Yerba Buena site in two significant ways. Much of the coastal terrain of the western United States is known as ‘suspect terrain,’ a landscape created by the deposition of sedimentary materials on the sea floor and the subsequent process of accretion activated by plate tectonics. These sediments were layered against the North American continent over millions of years to produce the Coast Ranges and related topography. The descending ship image is a metaphor for the long, slow process of deposition, the settling of sediment from the land onto the sea floor (the seasons and cycles of drifting materials), later to be returned to the land by the accretion process. Besides its physical proximity, the coast of California is intimately connected to the sea by the materials of which it is made. Deep Gradient... also responds to a structural condition of the site at Yerba Buena that exists on two levels: the landscape and architecture seen at street level and the cavernous convention center below. There is little or no reference to the lower level on the ground or promenade level; this upper level is essentially the illusion of a solid landscape complete with trees, rocks and buildings. The plane of material between these two worlds is seen as the surface of a ‘sea’ with the analogous theme of the sky above and the abyss below. The ship conceptually "descends’ into or ‘rises’ out of this abyss. The view ports visually extend this relationship by allowing obscured glimpses of this lower realm.

John Roloff, 1997 (revised)


"...Roloff has contributed a visually striking and philosophically resonate work...a piece of biological archaeology, and the glass structure is a giant time it will environment mediated between that not-so-distant past and the present."

--Bonetti, David, "Magnificent Enhancement of Public Realm,"

San Francisco Examiner, Oct. 15, 1993, pg. D-15.