HR: 1400h
AN: ED73B-06    [Abstracts]
TI: In-Class Quantification of the Mentos and Diet Coke Analogue Experiment: Effects of Wind on Volcanic Isopach Patterns
AU: * Quane, S
EM: steve.quane@gmail.com
AF: Colorado College, 14 E. Cache La Poudre St., Colorado Springs, CO 80903, United States
AU: Klos, Z
AF: Colorado College, 14 E. Cache La Poudre St., Colorado Springs, CO 80903, United States
AU: Jacobsen, R
AF: Colorado College, 14 E. Cache La Poudre St., Colorado Springs, CO 80903, United States
AB: The Mentos and Diet Coke experiment, where instantaneous emplacement of Mentos candy in Diet Coke creates a soda/CO₂ eruptive plume, is a common educational analogue for a volcanic eruption. In this paper, we quantify the effects of varying directional wind speeds on the eruptive plume as a learning tool in advanced Introductory Geology and Volcanology courses. The Mentos and Diet Coke reaction is a fun, safe and affordable analogue for explosive, single pulse, basaltic eruptions (e.g., Strombolian eruptions). Specifically, the physical and chemical reaction nucleating CO₂ bubbles on the pitted surface of Mentos candy is directly analogous to the collapsing foam eruption regime described by Parfitt (2004) where inertia driven fragmentation of the liquid (Namiki and Manga, 2008) leads to basaltic pyroclastic eruptions. Often, in these systems, the pyroclasts are carried downwind, resulting lopsided (downwind side taller) cinder cones. In our experiments, we create a single pulse eruption by simultaneously dropping four Mentos candies into a 16.9 oz. bottle of Diet Coke. The experiments are run under different wind conditions created by three stacked box fans in the off (control experiment) low, medium and high settings. Wind speed is measured using a hand held anemometer. The pyroclast dispersal is recorded by degree of liquid saturation through four layers of newspaper. The liquid is allowed to soak in for thirty seconds post eruption and then the individual layers of newspaper are separated and the saturation envelope is traced with a black marker and digitally photographed. The pyroclast dispersal envelope (or saturation area) is then quantified from the photos by image analysis in Adobe Photoshop. In addition, the experiments are videotaped to quantify ejection velocity using frame by frame analysis in iMovie. The resulting isopach ("deposit thickness") maps indicate a strong tightening of dispersal envelopes with increasing wind speed as seen in natural volcanic systems. Ongoing work is being done to scale the ejection velocities and dispersal envelope area up to natural eruptions. This simple and fun experiment brings a quantitative element to an experiment that is often limited to a show and tell exercise. In addition to covering the fundamental concepts of ejection velocity and isopach envelopes during explosive eruptions, it also exposes students to quantitative image and video analysis.
DE: 0820 Curriculum and laboratory design
DE: 0825 Teaching methods
SC: Education and Human Resources [ED]
MN: 2009 Joint Assembly