Granular disintegration of marble in nature: A thermal-mechanical origin for a grus and corestone landscape

Eppes, Martha Cary; Griffing, David H.

doi:10.1016/j.geomorph.2009.11.028

Cited by 36 publications

(19 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Assumptions and simplifications in the model include the following: We limit attention to grain‐scale subcritical cracking on subaerially exposed rock surfaces that—on the scale of grain‐size cracks—are nominally flat. Thus, we focus solely on formation of intergranular surface cracks having initial lengths, a o , on the order of the characteristic grain size, d g . This assumption is consistent with the observation that microfracture lengths in unweathered rock are typically on the order of the constituent grain size [ Nasseri et al , ]. Further, we assume that the characteristic critical crack length, a c , is also on the order of the characteristic grain size, again a reasonable assumption given the abundant field and laboratory evidence of the general propensity for rocks to granularly disaggregate [ Eppes and Griffing , ; Gómez‐Heras et al , ; Goudie , ; Siegesmund et al , ]. Thus, our modeling is limited to one—albeit common—style of rock cracking, granular disaggregation (Figure a). We use order of magnitude calculations to address the growth of cracks from their initial lengths to their critical lengths.…”

Section: Climate‐dependent Subcritical Cracking Modelmentioning

confidence: 82%

Mechanical weathering and rock erosion by climate‐dependent subcritical cracking

Eppes

Keanini

2017

Reviews of Geophysics

204

150

View full text Add to dashboard Cite

This work constructs a fracture mechanics framework for conceptualizing mechanical rock breakdown and consequent regolith production and erosion on the surface of Earth and other terrestrial bodies. Here our analysis of fracture mechanics literature explicitly establishes for the first time that all mechanical weathering in most rock types likely progresses by climate‐dependent subcritical cracking under virtually all Earth surface and near‐surface environmental conditions. We substantiate and quantify this finding through development of physically based subcritical cracking and rock erosion models founded in well‐vetted fracture mechanics and mechanical weathering, theory, and observation. The models show that subcritical cracking can culminate in significant rock fracture and erosion under commonly experienced environmental stress magnitudes that are significantly lower than rock critical strength. Our calculations also indicate that climate strongly influences subcritical cracking—and thus rock weathering rates—irrespective of the source of the stress (e.g., freezing, thermal cycling, and unloading). The climate dependence of subcritical cracking rates is due to the chemophysical processes acting to break bonds at crack tips experiencing these low stresses. We find that for any stress or combination of stresses lower than a rock's critical strength, linear increases in humidity lead to exponential acceleration of subcritical cracking and associated rock erosion. Our modeling also shows that these rates are sensitive to numerous other environment, rock, and mineral properties that are currently not well characterized. We propose that confining pressure from overlying soil or rock may serve to suppress subcritical cracking in near‐surface environments. These results are applicable to all weathering processes.

show abstract

Section: Climate‐dependent Subcritical Cracking Modelmentioning

confidence: 82%

Mechanical weathering and rock erosion by climate‐dependent subcritical cracking

Eppes

Keanini

2017

Reviews of Geophysics

204

150

View full text Add to dashboard Cite

show abstract

“…(): surface parallel fractures (spalling), fabric parallel fractures, longitudinal fractures (those parallel to the long‐axis of the rock), and intergranular fractures. For the latter cracks, thermal stress is known to lead to granular disaggregation, particularly in coarse‐grained rocks (Gómez‐Heras et al ., ; Eppes and Griffing, ), and we see evidence for such cracking along mineral grain boundaries in this study, particularly in the relatively coarse, quartz rich metamorphic rocks of the North Carolina site. We see less granular disaggregation and more spalling in the fine grained, darker rocks of the Pennsylvania sites overall, as would be expected from this previous work.…”

Section: Discussionmentioning

confidence: 97%

The influence of solar‐induced thermal stresses on the mechanical weathering of rocks in humid mid‐latitudes

Aldred

Eppes

Aquino

et al. 2015

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

The role of solar-induced thermal stresses in the mechanical breakdown of rock in humid-temperate climates has remained relatively unexplored. In contrast, numerous studies have demonstrated that cracks in rocks found in more arid midlatitude locations exhibit preferred northeast orientations that are interpreted to be a consequence of insolation-related cracking. Here we hypothesize that similar insolation-related mechanisms may be efficacious in humid temperate climates, possibly in conjunction with other mechanical weathering processes. To test this hypothesis, we collected rock and crack data from a total of 310 rocks at a forested field site in North Carolina (99 rocks, 266 cracks) and at forested and unforested field sites in Pennsylvania (211 rocks, 664 cracks) in the eastern United States. We find that overall, measured cracks exhibit statistically preferred strike orientations (47°± 16), as well as dip angles (52°± 24°), that are similar in most respects to comparable datasets from mid-latitude deserts. There is less variance in strike orientations for larger cracks suggesting that cracks with certain orientations are preferentially propagated through time. We propose that diurnally repeating geometries of solar-related stresses result in propagation of those cracks whose orientations are favorably oriented with respect to those stresses. We hypothesize that the result is an oriented rock heterogeneity that acts as a zone of weakness much like bedding or foliation that can, in turn, be exploited by other weathering processes. Observed crack orientations vary somewhat by location, consistent with this hypothesis given the different latitude and solar exposure of the field sites. Crack densities vary between field sites and are generally higher on north-facing boulder-faces and in forested sites, suggesting that moisture-availability also plays a role in dictating cracking rates. These data provide evidence that solar-induced thermal stresses facilitate mechanical weathering in environments where other processes are also likely at play.

show abstract

“…Delbo et al () have attempted to resolve this confusion by casting their framework in terms of microscopic (grain‐scale) thermal stresses and macroscopic (boulder‐scale) thermal stresses; both of which may operate simultaneously on airless planetary bodies in the inner solar system. Indeed, the macroscopic (rock‐scale) stress is the driving force for N‐S oriented cracks observed on the Earth surface (Eppes et al, ; Eppes et al, ; McFadden et al, ), while the microscopic one is the root of granular disintegration in Earth rocks (Eppes & Griffing, ; Gómez‐Heras, Smith, & Fort, ; Hall & André, ). The fact that both mechanisms may be operating simultaneously makes linear scaling of Basilevsky et al () particularly problematic.…”

Section: The Continuum Mechanics Perspective On Thermal Stresses and mentioning

confidence: 99%

Unraveling the Mechanics of Thermal Stress Weathering: Rate‐Effects, Size‐Effects, and Scaling Laws

et al. 2019

View full text Add to dashboard Cite

Thermal stress weathering is now recognized to be an active and significant geomorphological process on airless bodies. This study aims to understand the key factors governing thermal stresses in rocks on airless bodies through extensive numerical calculations and analytic analyses. Microscopic (grain‐scale) thermal stresses are driven primarily by the maximum diurnal temperature variation at said depth. Macroscopic (rock‐scale) thermal stresses are more complex. For rock sizes larger than the thermal skin depth, macroscopic thermal stresses are driven primarily by second (and higher) order spatial gradients of temperature. For rock sizes smaller than the thermal skin depth, macroscopic thermal stresses are primarily driven by the ratio of rock size to thermal skin depth. Additionally, scaling relations for diurnal surface temperature variation, time‐rate‐of‐change of surface temperature, as well as peak microscopic (grain‐scale) and macroscopic (rock‐scale) thermal stresses are derived to provide a more accessible modeling tool. These scaling relations are remarkably accurate when compared to both the numerical calculations as well as three‐dimensional finite element calculations. The model formulation, results, and scaling relations provided here allow the estimation of diurnal temperatures and thermal stresses on rocks of various size and materials on airless bodies at any orbital distance with a broad spectrum of spin rates. Lastly, we postulate and confirm that there is a critical spin rate where macroscopic thermal stresses will be greatest.

show abstract

Granular disintegration of marble in nature: A thermal-mechanical origin for a grus and corestone landscape

Cited by 36 publications

References 36 publications

Mechanical weathering and rock erosion by climate‐dependent subcritical cracking

Mechanical weathering and rock erosion by climate‐dependent subcritical cracking

The influence of solar‐induced thermal stresses on the mechanical weathering of rocks in humid mid‐latitudes

Unraveling the Mechanics of Thermal Stress Weathering: Rate‐Effects, Size‐Effects, and Scaling Laws

Contact Info

Product

Resources

About