scholarly journals Anisovolumetric weathering in granitic saprolite controlled by climate and erosion rate

Geology ◽  
2021 ◽  
Author(s):  
Clifford S. Riebe ◽  
Russell P. Callahan ◽  
Sarah B.-M. Granke ◽  
Bradley J. Carr ◽  
Jorden L. Hayes ◽  
...  
Keyword(s):  
Mass Loss ◽  
Multiple Regression ◽  
Sierra Nevada ◽  
Land Surface ◽  
Erosion Rate ◽  
Volumetric Strain ◽  
Physical Strain ◽  
Physical Weathering ◽  
Soil Weathering ◽  
Erosion Rates

Erosion at Earth’s surface exposes underlying bedrock to climate-driven chemical and physical weathering, transforming it into a porous, ecosystem-sustaining substrate consisting of weathered bedrock, saprolite, and soil. Weathering in saprolite is typically quantified from bulk geochemistry assuming physical strain is negligible. However, modeling and measurements suggest that strain in saprolite may be common, and therefore anisovolumetric weathering may be widespread. To explore this possibility, we quantified the fraction of porosity produced by physical weathering, FPP, at three sites with differing climates in granitic bedrock of the Sierra Nevada, California, USA. We found that strain produces more porosity than chemical mass loss at each site, indicative of strongly anisovolumetric weathering. To expand the scope of our study, we quantified FPP using available volumetric strain and mass loss data from granitic sites spanning a broader range of climates and erosion rates. FPP in each case is ≥0.12, indicative of widespread anisovolumetric weathering. Multiple regression shows that differences in precipitation and erosion rate explain 94% of the variance in FPP and that >98% of Earth’s land surface has conditions that promote anisovolumetric weathering in granitic saprolite. Our work indicates that anisovolumetric weathering is the norm, rather than the exception, and highlights the importance of climate and erosion as drivers of subsurface physical weathering.

scholarly journals Porosity production in weathered rock: Where volumetric strain dominates over chemical mass loss

2019 ◽  
Vol 5 (9) ◽  
pp. eaao0834 ◽  
Author(s):  
Jorden L. Hayes ◽  
Clifford S. Riebe ◽  
W. Steven Holbrook ◽  
Brady A. Flinchum ◽  
Peter C. Hartsough
Keyword(s):  
Mass Loss ◽  
Sierra Nevada ◽  
Volumetric Strain ◽  
Critical Zone ◽  
Chemical Components ◽  
Relative Importance ◽  
Conventional View ◽  
Biotite Weathering ◽  
Physical And Chemical ◽  
Geophysical Measurements

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.

scholarly journals Erosion rates as a potential bottom‐up control of forest structural characteristics in the Sierra Nevada Mountains

Ecology ◽  
2015 ◽  
Vol 96 (1) ◽  
pp. 31-38 ◽  
Author(s):  
David T. Milodowski ◽  
Simon M. Mudd ◽  
Edward T. A. Mitchard
Keyword(s):  
Sierra Nevada ◽  
Structural Characteristics ◽  
Bottom Up ◽  
Erosion Rates ◽  
Sierra Nevada Mountains

scholarly journals Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using 137Cs techniques

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Shamsollah Ayoubi ◽  
Nafiseh Sadeghi ◽  
Farideh Abbaszadeh Afshar ◽  
Mohammad Reza Abdi ◽  
Mojtaba Zeraatpisheh ◽  
...  
Keyword(s):  
Land Use ◽  
Magnetic Susceptibility ◽  
Soil Erosion ◽  
Erosion Rate ◽  
Land Use Changes ◽  
Soil Samples ◽  
Natural Forest ◽  
Oak Forests ◽  
Erosion Rates ◽  
Rainfed Farming

Abstract Background As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods In this research, the Caesium-137 (137Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes. To achieve this goal, we select a representative area in the Lordegan district, central Iran. 137Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming. In each hillslope, soil samples from three depths (0–10, 10–20, and 20–50 cm) and in four different slope positions (summit, shoulder, backslope, and footslope) were taken in three transects of about 20 m away from each other. The activity of 137Cs was determined in all the soil samples (72 soil samples) by a gamma spectrometer. In addition, some physicochemical properties and the magnetic susceptibility (MS) of soil samples were measured. Results Erosion rates reached 51.1 t·ha− 1·yr− 1 in rainfed farming, whereas in the natural forest, the erosion rate was 9.3 t·ha− 1·yr− 1. Magnetic susceptibility was considerably lower in the cultivated land (χhf = 43.5 × 10− 8 m3·kg− 1) than in the natural forest (χhf = 55.1 × 10− 8 m3·kg− 1). The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one, compared to that in the rainfed farming land. The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming, respectively. Conclusions We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area. Moreover, land management can influence soil erosion intensity and may both mitigate and amplify soil loss.

scholarly journals Assessment of Soil Erosion Vulnerability in the Heavily Populated and Ecologically Fragile Communities in Motozintla De Mendoza, Chiapas, Mexico

2017 ◽  
Author(s):  
Selene B. González-Morales ◽  
Alex Mayer ◽  
Neptalí Ramírez-Marcial
Keyword(s):  
Soil Erosion ◽  
Erosion Rate ◽  
Negative Response ◽  
Attitudes And Practices ◽  
Erosion Rates ◽  
Soil Erosion Rate ◽  
Kap Survey ◽  
Level Of Knowledge ◽  
Steep Slopes ◽  
Knowledge Attitudes And Practices

Abstract. The physical aspects and knowledge of soil erosion in six communities in rural Chiapas, Mexico were assessed. Average erosion rates estimated with the RUSLE model ranged from 200 to 1,200 ha−1 yr−1. Most erosion rates are relatively high due to steep slopes, sandy soils and bare land cover. The lowest rates occur where corn is cultivated for much of the year and slopes are relatively low. The results of a knowledge, attitudes and practices (KAP) survey showed that two-thirds of respondents believed that the major cause of soil erosion was hurricanes or rainfall and only 14 % of respondents identified human activities as causes of erosion. Forty-two percent of respondents indicated that the responsibility for solving soil erosion problems lies with government, as opposed to 26 % indicating that the community is responsible. More than half of respondents believed that reforestation is a viable option for reducing soil erosion, but only a third of respondents were currently applying reforestation practices and another one-third indicated that they were not following any conservation practices. The KAP results were used to assess the overall level of knowledge and interest in soil erosion problems and their solutions by compiling negative responses. The community of Barrio Vicente Guerrero may be most vulnerable to soil erosion, since it had the highest average negative response and the second highest soil erosion rate. However, Poblado Cambil had the highest estimated soil erosion rate and a relatively low average negative response rate, suggesting that soil conservation efforts should be prioritized for this community. We conclude that as long as the economic and productive needs of the communities are not solved simultaneously, the risk of soil erosion will increase in the future, which threatens the survival of these communities.

scholarly journals Climate, snow, and soil moisture data set for the Tuolumne and Merced river watersheds, California, USA

2019 ◽  
Vol 11 (1) ◽  
pp. 101-110 ◽  
Author(s):  
James W. Roche ◽  
Robert Rice ◽  
Xiande Meng ◽  
Daniel R. Cayan ◽  
Michael D. Dettinger ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Sierra Nevada ◽  
Land Surface ◽  
Forest Canopy ◽  
Snow Water Equivalent ◽  
Process Models ◽  
Series Data ◽  
Climate Data ◽  
Data Set ◽  
Data Repositories

Abstract. We present hourly climate data to force land surface process models and assessments over the Merced and Tuolumne watersheds in the Sierra Nevada, California, for the water year 2010–2014 period. Climate data (38 stations) include temperature and humidity (23), precipitation (13), solar radiation (8), and wind speed and direction (8), spanning an elevation range of 333 to 2987 m. Each data set contains raw data as obtained from the source (Level 0), data that are serially continuous with noise and nonphysical points removed (Level 1), and, where possible, data that are gap filled using linear interpolation or regression with a nearby station record (Level 2). All stations chosen for this data set were known or documented to be regularly maintained and components checked and calibrated during the period. Additional time-series data included are available snow water equivalent records from automated stations (8) and manual snow courses (22), as well as distributed snow depth and co-located soil moisture measurements (2–6) from four locations spanning the rain–snow transition zone in the center of the domain. Spatial data layers pertinent to snowpack modeling in this data set are basin polygons and 100 m resolution rasters of elevation, vegetation type, forest canopy cover, tree height, transmissivity, and extinction coefficient. All data are available from online data repositories (https://doi.org/10.6071/M3FH3D).

scholarly journals Estimation of soil loss using remote sensing and GIS-based universal soil loss equation in northern catchment of Lake Tana Sub-basin, Upper Blue Nile Basin, Northwest Ethiopia

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Veera Narayana Balabathina ◽  
R. P. Raju ◽  
Wuletaw Mulualem ◽  
Gedefaw Tadele
Keyword(s):  
Remote Sensing ◽  
Land Use ◽  
Soil Erosion ◽  
Soil Loss ◽  
Erosion Rate ◽  
Soil Erodibility ◽  
Lake Tana ◽  
Erosion Rates ◽  
Soil Erosion Rate ◽  
Soil Loss Equation

Abstract Background Soil erosion is one of the major environmental challenges and has a significant impact on potential land productivity and food security in many highland regions of Ethiopia. Quantifying and identifying the spatial patterns of soil erosion is important for management. The present study aims to estimate soil erosion by water in the Northern catchment of Lake Tana basin in the NW highlands of Ethiopia. The estimations are based on available data through the application of the Universal Soil Loss Equation integrated with Geographic Information System and remote sensing technologies. The study further explored the effects of land use and land cover, topography, soil erodibility, and drainage density on soil erosion rate in the catchment. Results The total estimated soil loss in the catchment was 1,705,370 tons per year and the mean erosion rate was 37.89 t ha−1 year−1, with a standard deviation of 59.2 t ha−1 year−1. The average annual soil erosion rare for the sub-catchments Derma, Megech, Gumara, Garno, and Gabi Kura were estimated at 46.8, 40.9, 30.9, 30.0, and 29.7 t ha−1 year−1, respectively. Based on estimated erosion rates in the catchment, the grid cells were divided into five different erosion severity classes: very low, low, moderate, high and extreme. The soil erosion severity map showed about 58.9% of the area was in very low erosion potential (0–1 t ha−1 year−1) that contributes only 1.1% of the total soil loss, while 12.4% of the areas (36,617 ha) were in high and extreme erosion potential with erosion rates of 10 t ha−1 year−1 or more that contributed about 82.1% of the total soil loss in the catchment which should be a high priority. Areas with high to extreme erosion severity classes were mostly found in Megech, Gumero and Garno sub-catchments. Results of Multiple linear regression analysis showed a relationship between soil erosion rate (A) and USLE factors that soil erosion rate was most sensitive to the topographic factor (LS) followed by the support practice (P), soil erodibility (K), crop management (C) and rainfall erosivity factor (R). Barenland showed the most severe erosion, followed by croplands and plantation forests in the catchment. Conclusions Use of the erosion severity classes coupled with various individual factors can help to understand the primary processes affecting erosion and spatial patterns in the catchment. This could be used for the site-specific implementation of effective soil conservation practices and land use plans targeted in erosion-prone locations to control soil erosion.

scholarly journals Impact of change in erosion rate and landscape steepness on hillslope and fluvial sediments grain size in the Feather River Basin (Sierra Nevada, California)

2014 ◽  
Vol 2 (2) ◽  
pp. 1047-1092 ◽  
Author(s):  
M. Attal ◽  
S. M. Mudd ◽  
M. D. Hurst ◽  
B. Weinman ◽  
K. Yoo ◽  
...  
Keyword(s):  
Grain Size ◽  
River Basin ◽  
Sierra Nevada ◽  
Sediment Flux ◽  
Fluvial Sediments ◽  
Sediment Grain Size ◽  
Erosion Rates ◽  
Wide Range ◽  
Feather River ◽  
Order Of Magnitude

Abstract. The characteristics of the sediment transported by rivers (e.g., sediment flux, grain size distribution – GSD –) dictate whether rivers aggrade or erode their substrate. They also condition the architecture and properties of sedimentary successions in basins. In this study, we investigate the relationship between landscape steepness and the grain size of hillslope and fluvial sediments. The study area is located within the Feather River Basin in Northern California, and studied basins are underlain exclusively by tonalite lithology. Erosion rates in the study area vary over an order of magnitude, from > 250 mm ka−1 in the Feather River canyon to < 15 mm ka−1 on an adjacent low relief plateau. We find that the coarseness of hillslope sediment increases with increasing hillslope steepness and erosion rates. We hypothesize that, in our soil samples, the measured ten-fold increase in D50 and doubling of the amount of fragments larger than 1 mm when slope increases from 0.38 to 0.83 m m−1 is due to a decrease in the residence time of rock fragments, causing particles to be exposed for shorter periods of time to processes that can reduce grain size. For slopes in excess of 0.7 m m−1, landslides and scree cones supply much coarser sediment to rivers, with D50 and D84 more than one order of magnitude larger than in soils. In the tributary basins of the Feather River, a prominent break in slope developed in response to the rapid incision of the Feather River. Downstream of the break in slope, fluvial sediment grain size increases, due to an increase in flow competence (mostly driven by channel steepening) but also by a change in sediment source and in sediment dynamics: on the plateau upstream of the break in slope, rivers transport easily mobilised fine-grained sediment derived exclusively from soils. Downstream of the break in slope, mass wasting processes supply a wide range of grain sizes that rivers entrain selectively, depending on the competence of their flow. Our results also suggest that in this study site, hillslopes respond rapidly to an increase in the rate of base-level lowering compared to rivers.

The role of erosion in the morphometry of composite volcanoes

2021 ◽  
Author(s):  
Roos van Wees ◽  
Pierre-Yves Tournigand ◽  
Daniel O’Hara ◽  
Pablo Grosse ◽  
Gabor Kereszturi ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Age Determination ◽  
Morphometric Parameters ◽  
Physical Weathering ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Digital Elevation ◽  
Shape Complexity ◽  
Geochronological Constraints ◽  
Natural Composite

&lt;p&gt;Volcanoes are extremely dynamic landforms. They grow by the accumulation of eruptive products and intrusions and degrade by a range of erosion processes such as superficial runoff, chemical and physical weathering, fluvial and glacial incision, and mass movements. In this study, we aim at documenting and quantifying the morphology of natural composite volcanoes using a range of morphometric indices, to better understand the factors that control erosion rates and patterns.&lt;/p&gt;&lt;p&gt;In addition to standard morphometric indices, including edifice ellipticity and irregularity, computed by the MORVOLC algorithm, a fractal dimension tool is developed to quantitatively report the shape complexity of stratovolcanoes. A convex hull approach is used to derive minimal erosion volumes and estimate erosion rates, considering available geochronological constraints. Morphometric parameters are derived from digital elevation models (DEMs) for a few exemplary stratovolcanoes of contrasted ages from the same volcanic region. To analyse the potential bias induced by the selected DEMs and the identification of the volcanic edifice outline, we also conduct a sensitivity analysis. The morphometric parameters are similarly extracted using the freely and globally available ALOS 30m (AW3D30), SRTM 30m (SRTMGL1), and ASTER 30m (GDEM 003), and compared to values obtained with the TanDEM-X 12m. The subjective user-drawn edifice outlines are compared to outlines generated by available algorithms, i.e. NETVOLC and MBOA, and their impact on the accuracy of morphometric indexes is quantified. &amp;#160;&lt;/p&gt;&lt;p&gt;Our results highlight that erosion increases edifice irregularity and fractal dimension. Preliminary trends between volcano fractal dimension, eroded volume, and age suggest that fractal analysis has the potential to be used as a relative age determination tool. The proposed morphometric characterisation paves the way for a comparison between natural volcanoes and controlled lab experiments reproducing the degradation of pristine volcanic cones by surface runoff to be developed later in our project. &amp;#160;&lt;/p&gt;

scholarly journals Short Communication: Increasing vertical attenuation length of cosmogenic nuclide production on steep slopes negates topographic shielding corrections for catchment erosion rates

2018 ◽  
Author(s):  
Roman A. DiBiase
Keyword(s):  
Effective Mass ◽  
Erosion Rate ◽  
Attenuation Length ◽  
Erosion Rates ◽  
10Be Concentration ◽  
Shielding Factor ◽  
Cosmogenic 10Be ◽  
Topographic Shielding ◽  
Surface Production ◽  
Mass Attenuation

Abstract. Interpreting catchment-mean erosion rate from in situ produced cosmogenic 10Be concentration in stream sands requires calculating the catchment-mean 10Be surface production rate and effective mass attenuation length, both of which can vary locally due to topographic shielding and slope effects. The most common method for calculating topographic shielding accounts only for the effect of shielding at the surface, leading to catchment-mean corrections of up to 20 % in steep landscapes, and makes the simplifying assumption that the effective mass attenuation length for a given nuclide production mechanism is spatially uniform. Here I evaluate the validity of this assumption using a simplified catchment geometry to calculate the spatial variation in surface skyline shielding, effective mass attenuation length, and the total effective shielding factor for catchments with mean slopes ranging from 0° to 80°. For flat catchments (i.e., uniform elevation of bounding ridgelines), the increase in effective attenuation length as a function of hillslope angle and skyline shielding leads to a catchment-mean total effective shielding factor of one, implying that no topographic shielding factor is needed when calculating catchment-mean vertical erosion rates. For dipping catchments (as characterized by a plane fit to the bounding ridgelines), the catchment-mean total effective shielding factor is also one, except for cases of extremely steep range-front catchments, where the shielding correction is counterintuitively greater than one. These results indicate that in most cases, topographic shielding corrections are inappropriate for calculating catchment-mean erosion rates, and only needed for steep catchments with non-uniform distribution of quartz and/or erosion rate. By accounting only for shielding of surface production, existing shielding approaches introduce a slope-dependent systematic error that could lead to spurious interpretations of relationships between topography and erosion rate.

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