Quantifying long-term aeolian abrasion rates on hard rock surfaces

University Of Texas At Arlington, Arlington TX

Investigators

Abstract

In arid regions, on Earth and on other planets, wind-blown sand erodes and reshapes landscapes. On human timescales, this erosion can be immeasurably small, so it is unclear how long it takes to form these landscapes. This project will use two recent advances in geochemical measurements to measure erosion rates on southern Californian ventifacts, boulders which are eroded by sand blasting during windstorms. Based on these measurements, this project will investigate whether a past shift in climate produced different ventifact erosion rates. These measurements will also test whether erosion by wind-blown sand depends on rock type or height above the ground surface. Several reference rocks will be manually eroded at a known rate and then measured to test whether the predicted erosion rates based on geochemical measurements match the actual, known erosion rates. Finally, this project will create 3-D digital models of all ten studied ventifacts and make them freely available to educators everywhere with an accompanying teaching module. These boulders are rare and difficult to access, so creating photorealistic educational models dramatically increases access to these fascinating geological features. A limited supply of 3-D printed, handheld models will also be provided at no cost to interested classrooms and printing instructions will be posted online. The project goal is to quantify the spatial and temporal evolution of aeolian abrasion rates across the surface of ventifacts using recent advances in optically stimulated luminescence (OSL) and cosmogenic, in situ 10Be and 14C methods. Rates will be measured on lengths ranging from several mm to tens of cm and timescales from decadal to multi-millennial. This project involves five major research tasks: (1) field campaign to two sites in southern California; (2) in situ cosmogenic 14C-10Be exposure age and erosion rate analysis (1 paired 14C-10Be sample per ventifact, totaling 10); (3) OSL depth profile erosion rate analysis of ventifacts (10 OSL depth profiles per ventifact, totaling 100) and manually eroded rock cylinders (3 erosion rates per lithology and 10 lithologies, totaling 30); (4) generation of digital 3-D models from field photographs of 10 ventifacts using structure-from-motion photogrammetry and handheld educational models from 3-D printing along with an accompanying educational video; and (5) presentation of results at conferences and in peer-reviewed journal articles. Project results will demonstrate, for the first time, that luminescence measurements can accurately recover hard rock erosion rates on a mm-scale. Measured rates will benchmark existing but empirically untested abrasion mechanisms. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.