HR: 1340h
AN: NG33C-0185    [Abstracts]
TI: Scaling in columnar jointing of Southwestern British Columbia
AU: * Goehring, L
EM: goehring@physics.utoronto.ca
AF: University of Toronto, 60 St. George Street, Toronto, ON M5S1A7 Canada
AU: Morris, S W
EM: S.Morris@newton.cam.ac.uk
AF: University of Toronto, 60 St. George Street, Toronto, ON M5S1A7 Canada
AB: We are investigating the relationship between different length scales in columnar jointing, a phenomena whereby shrinkage cracks, slowly penetrating into a solidifying material, organize themselves into a (mostly) hexagonal set of prisms. Some famous examples of columnar joining are the Giant's Causeway in N. Ireland, and the Devil's Postpile in California. This type of self-organized fracture pattern is best known in flood basalts, however it is also ubiquitous in other types of lavas, and in experimentally amenable systems such as glasses and starch slurries. The pattern contains at least two natural length scales: the size of the columns themselves (as measured through edge length, diameter, or cross-section) and striae widths (a record of incremental advances of crack tips). We have collected field measurements of length scales from columnar jointing in Southwestern British Columbia, and use them to compare the two length scales for a variety of lava types. We compare these averages and striae series to measurements from the Columbia River Basalt Group to look for general scaling arguments for jointing in lavas. We also present measurements of striae widths as a function of distance from a flow margin, allowing us to test diffusive scaling arguments, and to extract information about the temperature and rock strength at the time of fracture.
DE: 4460 Pattern formation
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
DE: 5104 Fracture and flow
DE: 8429 Lava rheology and morphology
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005