Topographic stress and rock fracture
Water and biological activity attack bedrock at Earth’s surface, eroding the rock and forming life-sustaining soil. Water and life would have a hard time doing this without the intersecting networks of cracks, or fractures, that run through the bedrock underlying most landscapes. How deep do these fracture networks go, and does the topography of Earth’s surface play a role in forming them?
An intriguing hypothesis proposed decades ago is that topography perturbs subsurface stress fields, potentially altering bedrock fracture patterns and – because more fractured bedrock might erode more easily – creating feedbacks between topography, stress, fractures, and erosion. Seulgi Moon and Mirna Slim tested this hypothesis through collaborations with Steve Martel (U. Hawaii), Brad Goodfellow (Geological Survey of Sweden), Steve Holbrook (Virginia Tech), Kamini Singha (Colorado School of Mines), Diego Mas Ivars (SKB, Sweden) and others. In addition to uncovering evidence that topography does influence bedrock fracture abundance, Moon discovered that present-day stress fields and surface features can influence fracture patterns hundreds of meters below the land surface – much deeper than anticipated.
- Moon, S., J.T. Perron, S. Martel, W.S. Holbrook and J. St Clair (2017). A model of three-dimensional topographic stresses with implications for bedrock fractures, surface processes and landscape evolution. J. Geophys. Res., 122, 823-846, http://doi.org/10.1002/2016JF004155.
- Moon, S., J.T. Perron, S.J. Martel, B.W. Goodfellow, D. Mas Ivars, A. Simeonov, R. Munier, J.-O. Näslund, A. Hall, A.P. Stroeven, K. Ebert and J. Heyman (2020). Present-day stress field influences bedrock fracture openness in the deep subsurface. Geophys. Res. Lett., 47, e2020GL090581, https://doi.org/10.1029/2020GL090581.
- St. Clair, J., S. Moon, W.S. Holbrook, J.T. Perron, C.S. Riebe, S.J. Martel, B. Carr, C. Harmon, K. Singha and D. deB. Richter (2015). Geophysical imaging reveals topographic stress control of bedrock weathering, Science, 350, 534–538, http://doi.org/10.1126/science.aab2210.
- Slim, M., J.T. Perron, S.J. Martel and K. Singha (2015), Topographic stress and rock fracture: A two-dimensional numerical model for arbitrary surface topography and comparisons with borehole observations. Earth Surface Processes and Landforms, 40, 512–529, http://doi.org/10.1002/esp.3646.