Broadening theories of soils genesis: Insights from Tanzania and simple models

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dc.contributor.advisorLee, Cin-Ty A.en_US
dc.contributor.committeeMemberLuttge, Andreasen_US
dc.contributor.committeeMemberTomson, Mason B.en_US
dc.contributor.committeeMemberAnderson, John B.en_US
dc.contributor.committeeMemberEwing, Maurice W.en_US
dc.contributor.committeeMemberMasiello, Caroline A.en_US
dc.creatorLittle, Mark Gabrielen_US
dc.date.accessioned2014-09-18T16:05:26Zen_US
dc.date.available2014-09-18T16:05:26Zen_US
dc.date.issued2007en_US
dc.description.abstractThree basic assumptions of soil formation are challenged herein: the degree of chemical weathering decreases with depth; increased physical weathering due to high topographical gradients causes an increase in chemical weathering; and the mineral soil derives from the transformation of in situ parent material. The first part presents an investigation into the degree and nature of chemical weathering during soil formation on a volcanic substrate on Mt. Kilimanjaro in northern Tanzania. The degree of weathering was found to increase with depth in the soil profile. Observations show that the upper and lower layers of the weathering profile have undergone different weathering histories. The presence of a buried paleosol or enhanced weathering due to lateral subsurface water flow may explain the observations, the latter having novel implications for the transport of dissolved cations to the ocean. The second part presents a model to test the link between chemical weathering associated with soil formation and erosion associated with mass wasting. The predicted ratios suspended/dissolved ratios, however, are all higher than observed in rivers, the discrepancy worsening with increasing topographic relief. This discrepancy arises from the fact that in regions of high relief, mass wasting are so high that soil mantles do not reside on hillslopes long enough to allow for significant chemical weathering. The discrepancy between the model and observations can be explained by: over-estimate of predicted suspended load; absence of chemical weathering of deltaic/alluvial sediments from the model; or chemical weathering associated with groundwater weathering. The third part presents data from a sequential extraction on a basaltic soil from Mt. Meru in Northern Tanzania. The behavior of relatively immobile elements is consistent with soil formation being accompanied by mass loss due to chemical weathering. However, superimposed on this mass loss appears to be enrichment of most elements measured. These data suggest that the surface of the Meru soil columns may have experienced "re-fertilization" by the deposition of volcanic ash.en_US
dc.format.extent212 ppen_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.callnoTHESIS GEOL. 2008 LITTLEen_US
dc.identifier.citationLittle, Mark Gabriel. "Broadening theories of soils genesis: Insights from Tanzania and simple models." (2007) Diss., Rice University. <a href="https://hdl.handle.net/1911/77209">https://hdl.handle.net/1911/77209</a>.en_US
dc.identifier.digital304818077en_US
dc.identifier.urihttps://hdl.handle.net/1911/77209en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectEnvironmental scienceen_US
dc.subjectGeochemistryen_US
dc.subjectEarth sciencesen_US
dc.subjectSoilsen_US
dc.subjectTanzaniaen_US
dc.subjectWeatheringen_US
dc.subjectChemical weatheringen_US
dc.subjectAtmospheric depositionen_US
dc.titleBroadening theories of soils genesis: Insights from Tanzania and simple modelsen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentEarth Scienceen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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