8/24/2023 0 Comments Hawaiian tropic models 1971![]() 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).
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