Depth distribution and chemistry of salts as factors controlling tafoni and honeycombs development

Karatas, Tuna; Bruthans, Jiří; Filippi, Michal; Mazancová, Anna; Weiss, Tomáš; Mareš, Jakub

doi:10.1016/j.geomorph.2022.108374

Cited by 8 publications

(1 citation statement)

References 57 publications

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“…In order to quantitatively describe the formation of various shapes for concurrent rocks and to predict erosion in, for example, structures of building materials [53,54], it is necessary to measure material properties, such as moisture diffusivity D(θ) and the relative humidity of the surface material h m (θ), as functions of moisture content θ [55][56][57][58]. It is also necessary to validate the proposed physical and numerical model based on specific objects [59], by measuring seasonal changes in evaporation rate [60,61], the distribution of moisture and salts in the rock [62], and the position of the evaporation front [63]. It is also necessary to identify the influence of other factors that affect rock decay (chemical weathering [23], frost weathering [64], thermal shock [65], biological weathering [8], case hardening [4], erosion caused by the wind pressure [21], etc.).…”

Section: Resultsmentioning

confidence: 99%

Mathematical Simulation of Honeycomb Weathering via Moisture Transport and Salt Deposition

Safonov

Minchenkov

2023

Geosciences

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Honeycomb weathering is a common phenomenon found on various rock surfaces all around the world. However, honeycomb formation mechanisms are still poorly understood. In this study, we propose a model describing moisture transport within the sandstone and erosion resulting from salt deposition during evaporation of moisture off the rock surface. The moisture transport model is based on the non-linear diffusion equation, where the volumetric moisture content is a combined parameter accounting for the moisture and gas (vapor) content. The moisture transport model accounts for the several-orders-of-magnitude decrease in moisture diffusivity, observed during drying. It was assumed that erosion occurs when the evaporation front is located close to the rock surface. The depth of erosion is proportional to the moisture flow rate through the drying surface. The ABAQUS finite-element software suite was used for numerical solution of the non-linear diffusion equation. The iterative scheme of erosion simulation for different drying cycles was implemented using the Python programming language. Computations were conducted in the 2D setting for the square model with dimensions of 50 mm × 50 mm. Simulation results demonstrate the possibility of obtaining various landform shapes (honeycombs, tafoni) by varying only the value of the distribution of moisture content at the bottom side, simulating the rate of internal wetting of rock.

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Section: Resultsmentioning

confidence: 99%

Mathematical Simulation of Honeycomb Weathering via Moisture Transport and Salt Deposition

Safonov

Minchenkov

2023

Geosciences

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Moisture patterns and fluxes in evolving tafoni developed in arkosic sandstone in temperate climate

Mareš,

Bruthans,

Studencová

et al. 2024

Earth Surf Processes Landf

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Cavernous weathering forms have long been studied and discussed as enigmas in geomorphology. Recently, their evolution has been shown to be controlled by moisture patterns, which are still poorly understood. For the first time, capillary water and vapor fluxes were characterized in detail at tafone in a temperate climate of central Europe using a wide range of methods adapted from soil hydrology. Time domain reflectometry showed that moisture flows from the rock interior to the evaporation front in the shallow subsurface of both — the backwalls and the outer surface. When overland flow occurs on the outer surfaces (after heavy rains), 10 mm/day can infiltrate and flow toward the backwalls. The main sources of water for tafone are the influx of water from the rock interior and the infiltration of overland flow after heavy rains, while condensation of air humidity is a minor source. Influx from the rock interior is coupled to the evaporation rate, which varies between 100 and 300 kg/m2/year in summer and less than 15 kg/m2/year in winter. More water evaporates from the backwall of the tafone than from the outer surface, and more salt is deposited in the backwalls, resulting in predominant salt weathering in the backwalls. The tafoni studied thus evolve, and the cavities deepen. Tafoni in arid and semi‐arid environments generally show a much higher contrast between evaporation rates from backwalls and outer surfaces than tafoni and honeycombs in temperate and coastal environments. Tafoni in temperate settings are therefore more susceptible to degradation when evaporation decreases or inflow to the tafone increases. This study also shows that microtensiometers can be used to determine moisture content with high spatial resolution, while time domain reflectometry allows accurate characterization of moisture patterns with depth.

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Determining pore size distribution in rocks using shear‐thinning fluids: Utilisation of the method in geomorphology

Martin,

Martin

et al. 2024

Earth Surf Processes Landf

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The pore space characteristics of geological materials are closely related to their mechanical, transport and hydraulic properties. In geomorphology, pore size distribution (PSD) is an important characteristic in rock weathering, evaporation and other studies. In an effort to find novel methods to determine the PSD, perhaps to bypass the disadvantages of the current techniques, there has been a growing interest in the use of non‐Newtonian fluids. In this contribution, we are particularly interested in the method recently introduced by Abou Najm and Atallah (the ANA method), which exploits the way in which the flow of different shear‐thinning fluids distributes differently in the pore space to compute the functional PSD estimation. We performed a set of saturated flow experiments with aqueous xanthan gum solutions of different concentrations, using as simple as possible laboratory settings, and we implemented a modified version of the previously introduced numerical model to obtain the PSDs of four sandstone and one tuff samples. The results are compared with conventional mercury intrusion porosimetry, showing a good agreement regarding the dominant pore size and a notable similarity in the distributions. Several limitations were identified as well, such as the lack of information on relatively small pores (<5–10 μm for the samples studied) and the potential issues in obtaining a more detailed distribution. We conclude that the ANA method is promising for geomorphological evaporation and rock durability studies, particularly for coarser materials such as sandstone, but it also encounters challenges for certain applications, especially for fine‐grained rocks. It must be acknowledged that the ANA method has been tested on a limited range of materials and further investigation is required to fully explore its capabilities and limitations.

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Depth distribution and chemistry of salts as factors controlling tafoni and honeycombs development

Cited by 8 publications

References 57 publications

Mathematical Simulation of Honeycomb Weathering via Moisture Transport and Salt Deposition

Mathematical Simulation of Honeycomb Weathering via Moisture Transport and Salt Deposition

Moisture patterns and fluxes in evolving tafoni developed in arkosic sandstone in temperate climate

Determining pore size distribution in rocks using shear‐thinning fluids: Utilisation of the method in geomorphology

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