There are two ways in which oil can be transferred to the chamber: by surface creep
along the inner walls of the pumping line, and by oil vapor backstreaming into the chamber.
Recently developed methodology (Fryrear et al.) and field equipment, such as airborne dust samplers (Fryrear, 1986), surface creep and saltation samplers (Stout and Fryrear), and the SENSIT wind erosion sensor (Gillette and Stockton), have provided mechanisms to describe field erosion losses on a single storm basis.
Department of Agriculture at Big Spring, Texas, using equations for vertical distribution of material moving in saltation and surface creep (Fryrear; Fryrear et al.; Vories and Fryrear) and horizontal distribution of material across an eroding surface (Fryrear et al.; Stout) was used for this analysis.
EASTERLY winds moving in from the Columbia River gorge were creating a relentless movement of sand, or surface creep, on a mammoth surcharge area at Portland International Airport--and causing plenty of trouble in the process.
The action of the wind on surface creep was most detrimental in the first 100 ft around the total area.
The USGS issued the March 19 alert after two instruments detected a substantial acceleration in the normally slow surface creep
along the fault.