![]() ![]() ![]() Tropical saprolites typically have low shear wave velocities ( V S) of ∼300 m/s ( Yaede et al., 2015), corresponding to seismic design site class D (stiff soil NEHRP, 2003). Laterites have been investigated as ore deposits for Al, Fe, Ni, Au, Nb, and P (e.g., Meyer et al., 2002 Gleeson et al., 2004 Freyssinet et al., 2005). Laterites play a number of important roles in the tropics in terms of economic deposits, engineering, long-term regulation of the climate, and solute fluxes. This study shows how weathering features and processes may be synthesized from outcrop, geochemical observations, and geophysical profiles into a multi-stage conceptual model of weathering. Thus, differential weathering is a natural consequence of textural variations in primary igneous stratigraphy with superimposed additions of Al and Fe from the dissolution of basaltic glass. Second, the dense cores of a’a flows with widely spaced joints preserve large core stones that weather inward where halloysite-rich saprolite gives way to smectite-rich rims. First, although there is an overall trend for the downward migration of the weathering front with time, zones of high initial permeability (rubble above or below a’a flows tephra or scoria deposits) are influenced by both downward and lateral fluxes of water, leading to enhanced weathering in what are now gibbsite-rich horizons. Parallel to the paleo–lava flow direction, relict igneous stratigraphy is expressed as seaward-dipping reflectors on CDP profiles, whereas perpendicular to flow, reflector geometry suggests lenticular bodies within laterite.Ī synthesis of geochemistry and geophysical studies leads to the development of a conceptual model to explain variable weathering within the CZ. In addition to identifying the depth of the weathering front, stiff horizons within the laterite correlate to high gibbsite abundances in the MASW profile. Shear-wave velocity data derived from multichannel analysis of surface waves (MASW) and common depth point (CDP) seismic reflection profiles reveal important internal details of the weathering profiles that complement information derived from nearby rock outcrop along a sea cliff. Excess Al and Fe found in soil and saprolite likely originated from the decomposition of volcanic ash deposited on the ground surface from later effusive volcanism. At the base of the weathering front and on the rinds of core stones, transient smectite clays are developed, but rapidly break down to halloysite. Gibbsite-rich horizons occur in enhanced zones of weathering. Laterite development includes the entire vadose zone, with a mineralogy that chiefly includes halloysite ± gibbsite and Fe-oxides and mixed Fe-oxides and hydroxide species developed on a 303 ka substrate. In the Kohala Peninsula, Hawaii, a variably weathered, thick soil and saprolite profile is exposed along sea cliffs in a mesic climate setting. The purpose of this study is to develop a model for rapid weathering to deep regolith profiles in tropical ocean islands. The Hawaiian Islands (USA) make an excellent natural laboratory for examining the tropical CZ, where the bedrock composition (basalt) is nearly uniform but of variable age and where climate (rainfall) varies greatly. These areas are widespread in the tropics and compose an important component of the critical zone (CZ). Penn St.Much of the world’s population lives in developing countries in regions with deeply weathered soils and thick, subjacent saprolites. ![]() More famous alumni from the College Wires Network:Īla / Ark / Aub / Fla / LSU / Tenn / TX A&M / UGA // Iowa / Mich / Mich St. Information pertaining to alumni and attendees are from Volopedia, University of Tennessee Digital Encyclopedia, and UTK Alumni. Vols Wire looks at notable alumni and attendees throughout the history of the University of Tennessee. Innovation: We continuously improve, create, and boldly strive for excellence in our work.Inclusion: We value diversity and welcome alternative perspectives in all we do.Integrity: We maintain the highest level of accountability through honest and transparent interactions.Collaboration: We build relationships and strong partnerships to advance the university.We cherish the university’s rich and vibrant history and enhance its reputation. Throughout its history, notable individuals have earned degrees at the University of Tennessee. The University of Tennessee in Knoxville, Tennessee was founded in 1794. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |