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Title: Rates of subcritical cracking and long-term rock erosion

Abstract

Bedrock fracture is a key element of rock erosion and subsequent surface processes. We test the hypothesis that rock's susceptibility to subcritical cracking, a specific type of fracturing, significantly drives and limits rock erosion. We measured 10Be-derived erosion rates, compressive strength, and crack characteristics on 20 outcrops of different rock units (quartzite, granite, and two metasandstones) in the northern Blue Ridge Mountains of Virginia (USA). We also measured the subcritical cracking index (n), Charles’s law velocity constant (A), and fracture toughness (K IC) of samples from four of the same outcrops, representative of each rock type. Erosion rates range from 1.16 ± 0.67 to 32.3 ± 7.8 m/m.y. We find strong correlations—across the four rock units—between average erosion rates and the three subcritical cracking parameters (R 2 > 0.85, p < 0.05), but not compressive strength (R 2 = 0.6; p > 0.1). We also find a correlative relationship between n and outcrop fracture length (R 2 = 0.91; p < 0.05). The latter correlation is consistent with that of published model predictions, further indicating a mechanistic link between subcritical cracking and rock erosion. We infer that subcritical cracking parameters closely tie to erosion rates, because subcritical cracking is themore » dominant process of mechanical weathering, leading to positive feedbacks relating subcritical cracking rates, crack length, porosity, and water accessibility. Finally, these data are the first that directly test and support the hypothesis that subcritical cracking can set the pace of long-term rock erosion.« less

Authors:
 [1];  [2];  [3];  [1];  [4];  [2];  [1];  [1];  [1];  [1];  [2]
  1. Univ. of North Carolina, Charlotte, NC (United States). Dept. of Geography and Earth Sciences
  2. College of William and Mary, Williamsburg, VA (United States). Dept. of Geology
  3. Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology
  4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Univ. of Texas, Austin, TX (United States); Univ. of North Carolina, Charlotte, NC (United States); College of William and Mary, Williamsburg, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Fossil Energy (FE); United States Geological Survey (USGS); Univ. of North Carolina, Charlotte (United States); College of William and Mary (United States)
OSTI Identifier:
1477884
Report Number(s):
SAND-2018-9306J
Journal ID: ISSN 0091-7613; 667314
Grant/Contract Number:  
NA0003525; SC0006883; FE0023316
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geology
Additional Journal Information:
Journal Name: Geology; Journal ID: ISSN 0091-7613
Publisher:
Geological Society of America
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES

Citation Formats

Eppes, M. C., Hancock, G. S., Chen, X., Arey, J., Dewers, T., Huettenmoser, J., Kiessling, S., Moser, F., Tannu, N., Weiserbs, B., and Whitten, J. Rates of subcritical cracking and long-term rock erosion. United States: N. p., 2018. Web. doi:10.1130/G45256.1.
Eppes, M. C., Hancock, G. S., Chen, X., Arey, J., Dewers, T., Huettenmoser, J., Kiessling, S., Moser, F., Tannu, N., Weiserbs, B., & Whitten, J. Rates of subcritical cracking and long-term rock erosion. United States. doi:10.1130/G45256.1.
Eppes, M. C., Hancock, G. S., Chen, X., Arey, J., Dewers, T., Huettenmoser, J., Kiessling, S., Moser, F., Tannu, N., Weiserbs, B., and Whitten, J. Tue . "Rates of subcritical cracking and long-term rock erosion". United States. doi:10.1130/G45256.1. https://www.osti.gov/servlets/purl/1477884.
@article{osti_1477884,
title = {Rates of subcritical cracking and long-term rock erosion},
author = {Eppes, M. C. and Hancock, G. S. and Chen, X. and Arey, J. and Dewers, T. and Huettenmoser, J. and Kiessling, S. and Moser, F. and Tannu, N. and Weiserbs, B. and Whitten, J.},
abstractNote = {Bedrock fracture is a key element of rock erosion and subsequent surface processes. We test the hypothesis that rock's susceptibility to subcritical cracking, a specific type of fracturing, significantly drives and limits rock erosion. We measured 10Be-derived erosion rates, compressive strength, and crack characteristics on 20 outcrops of different rock units (quartzite, granite, and two metasandstones) in the northern Blue Ridge Mountains of Virginia (USA). We also measured the subcritical cracking index (n), Charles’s law velocity constant (A), and fracture toughness (KIC) of samples from four of the same outcrops, representative of each rock type. Erosion rates range from 1.16 ± 0.67 to 32.3 ± 7.8 m/m.y. We find strong correlations—across the four rock units—between average erosion rates and the three subcritical cracking parameters (R2 > 0.85, p < 0.05), but not compressive strength (R2 = 0.6; p > 0.1). We also find a correlative relationship between n and outcrop fracture length (R2 = 0.91; p < 0.05). The latter correlation is consistent with that of published model predictions, further indicating a mechanistic link between subcritical cracking and rock erosion. We infer that subcritical cracking parameters closely tie to erosion rates, because subcritical cracking is the dominant process of mechanical weathering, leading to positive feedbacks relating subcritical cracking rates, crack length, porosity, and water accessibility. Finally, these data are the first that directly test and support the hypothesis that subcritical cracking can set the pace of long-term rock erosion.},
doi = {10.1130/G45256.1},
journal = {Geology},
issn = {0091-7613},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {9}
}

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