ix, 44 p. : ill. (some col.) / The physical weathering of rock in cryogenic regions through a process called ice segregation is important for understanding subglacial processes, landscape evolution and cold region engineering. Ice segregation was examined by freezing water-saturated cores of Eugene Formation sandstone at temperatures between -15° and -2°C. Cores between -8° and -5°C took 30-45 minutes to crack, while cores at warmer or cooler temperatures took either more than 90 minutes or did not crack at all. Numerical modeling shows that cores break under isothermal conditions. The results of this study suggest that previous models in which temperature gradients are held responsible for driving flow towards growing cracks are incomplete. I introduce a new model of ice segregation to explain how premelted liquids from smaller pores can migrate and contribute to the growth of large cracks. This dissertation includes unpublished material. / Committee in charge: Alan Rempel, Chairperson; Joshua Roering, Member; Rebecca Dorsey, Member