61 research outputs found
Reservoir theory for studying the geochemical evolution of soils
Full text linkLinking mineral weathering rates measured in the laboratory to those measured at the landscape scale is problematic. In laboratory studies, collections of minerals are exposed to the same weathering environment over a fixed amount of time. In natural soils, minerals enter, are mixed within, and leave the soil via erosion and dissolution/leaching over the course of soil formation. The key to correctly comparing mineral weathering studies from laboratory experiments and field soils is to consistently define time. To do so, we have used reservoir theory. Residence time of a mineral, as defined by reservoir theory, describes the time length between the moment that a mineral enters (via soil production) and leaves (via erosion and dissolution/leaching) the soil. Age of a mineral in a soil describes how long the mineral has been present in the soil. Turnover time describes the time needed to deplete a species of minerals in the soil by sediment efflux from the soil. These measures of time are found to be sensitive to not only sediment flux, which controls the mineral fluxes in and out of a soil, but also internal soil mixing that controls the probability that a mineral survives erosion. When these measures of time are combined with published data suggesting that a mineral's dissolution reaction rate decreases during the course of weathering, we find that internal soil mixing, by partially controlling the age distribution of minerals within a soil, might significantly alter the soil's mass loss rate via chemical weathering.</p
Simplistic hydrodynamic modelling and multispectral image classification: predicting floodwater response to cyclonic precipitation in Southern Mexico
No full textWith an increase in the probability of more severe precipitation events predicted by multiple climate change models, the necessity to accurately and efficiently identify a large coverage of areas at risk of flood damage is imperative. The increasing coverage and availability of very high resolution topographic data has aided the rapid development of high quality floodplain delineation and flood susceptibility mapping. However, the importance of the spatial variability of precipitation data applied in realistic hydrodynamic modelling of increased hurricane activity remains largely unexplored. This study applies a novel set of algorithms to a 372km2 area of topographic data derived from Light Detection and Ranging in Southwest Mexico, to investigate the influence cyclonic precipitation morphology has on floodwater flow predictions. An automatic floodplain delineation algorithm is run to objectively identify flood-susceptible catchments, before a cellular automaton model is applied to simulate inundation resulting from Hurricane Max, a Category 1 hurricane that occurred in September 2017. Using gridded Global Precipitation Measurement rainfall rate data and a Sentinel-2B multispectral satellite image captured immediately following the hurricane event, this study investigates to what extent remotely sensed data can be applied successfully to emulate a flood event and calibrate hydrodynamic flow model parameters to predict future inundation. It was found that simulated floodwater runoff from spatially variable incoming rainfall has a higher spatial intersection with the automatically classified water body pixels from the multispectral image. Additionally, the cellular automaton model simulated a higher peak discharge and greater extent of shallow floodwater depths in the river response to spatially variable incoming rainfall scenario compared to uniform rainfall. The results highlight the need for future consideration of precipitation morphology in flood modelling, and support the use of high abstraction models of Earth’s surface processes and fluvial hazard mitigation in data-sparse regions
Characteristics of wind waves in shallow tidal basins and how they affect bed shear stress, bottom erosion, and the morphodynamic evolution of coupled marsh and mudflat landforms
No full textInfluence of chemical denudation on hillslope morphology
Full text link[1] Models of hillslope evolution involving diffusion-like sediment transport are conventionally presented as an equation in which the changes in land-surface elevation or soil thickness are balanced by the divergence of soil transport and tectonic uplift, soil production, or both. These models typically do not include the loss or gain of mass in hillslope soils due to processes of chemical weathering and deposition. We formulate a more general depth-integrated equation for the conservation of soil mass on a hillslope that includes a term representing chemical deposition or denudation. This general depth-integrated equation is then simplified to determine the one-dimensional form of a steady state hillslope which experiences both mechanical and chemical denudation. The differences in morphology between hillslopes only experiencing diffusion-like mechanical sediment transport and hillslopes experiencing both diffusion-like mechanical sediment transport and chemical denudation are explored. Under the conditions of a downslope increase in local soil lowering rate due to chemical weathering the hillslope profile will depart from the parabolic shape predicted by models that incorporate only linear diffusion-like mechanical sediment transport. In addition, hillslopes that experience both chemica
Reading the recorded history of soil mantled hillslopes
No full textHillslope soils cover a large proportion of Earth’s terrestrial landscapes. This dissertation is a theoretical exploration of how chemical and mechanical processes affect the formation and dynamics of both hillslope soils and soil mantled landscapes. It explores how hillslopes adjust to time varying erosion rates. Statements of mass conservation for both the total soil layer and constitutive soil phases are derived that include terms describing both chemical and mechanical denudation. These statements are used to demonstrate that chemical processes are as important as mechanical processes in determining the morphology of landscapes, and that chemical properties of hillslope soils can be used to quantify chemical denudation rates. Analyses are performed for both the steady state case (where erosion rates do not change in time) and the transient case (where erosion rates are time-varying). Transient simulations show that hillslope soils respond to changes in channel incision over characteristic timescales, and changes in channel incision leave characteristic chemical and physical signatures on the landscape that last for tens of thousands to millions of years
. 79 (2011) mayo-agosto. Historias. Revista de la Dirección de Estudios Históricos
No full text- Revolución y profanación por Simon Schama. - Museo de escultura comparada por Marius Zayas. - La rebusca en las imágenes por William Taylor. - México y los huesos de sus héroes por Héctor de Mauleón. - Sin “cieno ni obscenidad”: el censor de películas Francisco Ortiz Muñoz, inventor de su propio paraíso (1946) por Julia Tuñón. - El doctor Merolico y la libertad de profesiones, 1879-1880 por Jesús Guzmán Urióstegui. - Una nación santa: de héroes y profetas por Jaime Cuadriello. - Mitohistoria y nación: a propósito de la España Primitiva de Huerta y Vega por Pablo Fernández Albaladejo. - El dogma trinitario, su iconografía, su bibliografía por María del Consuelo Maquívar. - El quehacer del ayuntamiento mexicano en el siglo XVIII por Esteban Sánchez de Tagle. - Unas beatas judías… por Antonio Rubial García. - La hechura del artista por Arturo Aguilar. - La “anti-ciudad” de los palacios por Jorge Olvera Ramos. – Crestomanía por José Mariano Leyva
LSDtopotools/MuddPILE: MuddPILE release 0.09
No full textUpdated version of MuddPILE used in deterministic runs December and January 2022.
Includes updated hillslope snapping and capping, alongside new transient simulation features.
To see the options available, type MuddPILE.out -h after compiling the software
Toward process-based modeling of geochemical soil formation across diverse landforms: A new mathematical framework
No full textDiscrepancy between mineral residence time and soil age: Implications for the interpretation of chemical weathering rates
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