Person to see: Dr. John Dixon (at the Deanery).
The feature item of the centrifuge lab is, not surprisingly, a large-capacity centrifuge used in scale-model studies of tectonic processes. The centrifuge is capable of spinning two models, each 76 x 127 mm (3 x 5º) in plan and up to 51 mm (2º) high at speeds up to 7200 rpm (corresponding to 20,000g). At these high accelerations, stacked layers of plasticine and silicone putty are appropriate analogues for bedded sedimentary successions at the basin scale. Deformation of the models is either a consequence of incorporated gravitational instabilities or is achieved by a gravitationally faked push from the rear. The 3-D evolution of the model structures can be studied by examining sections cut through them after successive increments of deformation. Processes investigated to date include gravity spreading, diapirism, and most recently, structural development in foreland fold/thrust belts.
The guts of the centrifuge is a 100kg aluminium rotor 864 mm (34º) across enclosed in an inch thick steel safety chamber. The model holders are cavities milled in diametrically opposite positions in the rotor, not swinging cups, so they can hold only solid materials (it's no good for getting the sediment out of your homebrew). Deformation of the top surface of either model can be viewed on a monitor and recorded on video cassette courtesy of a TV camera and strobe system. Control of maximum accelerations and run times is either manual or can be programmed using the venerable Commodore PET computer ( a whopping 32k of RAM) which can also record and print data (temperatures, strains) from sensors in the model cavities. Lately, control has been manual. It's more fun. For more details on machine specifications, model scaling parameters and construction techniques, and applications, refer to Dixon and Summers (Journal of Structural Geology 7, 1985, 83-102), Dixon and Tirrul (Journal of Structural Geology 13, 1991, p. 3-20) and Liu and Dixon (Tectonophysics 188, 1991, p. 39-62). If you're interested in using the machine, contact Prof. John Dixon (ph. 2448 in the Deanery; 6172 in Miller 228).
RMH