Weathering in the critical zone causes volumetric strain and mass loss, thereby creating subsurface porosity that is vital to overlying ecosystems. We used geochemical and geophysical measurements to quantify the relative importance of volumetric strain and mass loss---the physical and chemical components of porosity---in weathering of granitic saprolite of the southern Sierra Nevada, California, USA. Porosity and strain decrease with depth and imply that saprolite more than doubles in volume during exhumation to the surface by erosion. Chemical depletion is relatively uniform, indicating that changes in porosity are dominated by processes that cause strain with little mass loss. Strain-induced porosity production at our site may arise from root wedging, biotite weathering, frost cracking, and the opening of fractures under ambient topographic stresses. Our analysis challenges the conventional view that volumetric strain can be assumed to be negligible as a porosity-producing mechanism in saprolite.

Hayes, Jorden L., Clifford S. Riebe, W. Steven Holbrook, Brady A. Flinchum, and Peter C. Hartsough. Porosity Production in Weathered Rock: Where Volumetric Strain Dominates Over Chemical Mass Loss. Science Advances 5, no. 9 (2019): eaao0834. https://advances.sciencemag.org/content/5/9/eaao0834

This is an Open Access article distributed under the terms of theCreative Commons Attribution-NonCommercial license, CC-BY-NC 4.0 license, https://creativecommons.org/licenses/by/4.0/, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

Open access publication of this article was made possible with grant support from Waidner-Spahr Library distributed through the Dickinson College Research & Development Committee.

Jorden Hayes is a professor of Geosciences at Dickinson College.

This published version is made available on Dickinson Scholar with the permission of the publisher. For more information on the published version, visit American Association for the Advancement of Science's Website. https://www.science.org/doi/10.1126/sciadv.aao0834