HR: 1340h
AN: ED13C-1153    [Abstracts]
TI: Volcanoes in the Classroom: Simulating an Eruption Column
AU: * Harpp, K S
EM: kharpp@mail.colgate.edu
AF: Geology Dept, Colgate Univ, Hamilton, NY 13346
AU: Geist, D J
EM: dgeist@uidaho.edu
AF: Geology Dept, Univ Idaho, Moscow, ID 83844
AU: Koleszar, A M
EM: alison_koleszar@brown.edu
AF: Geology Dept, Brown Univ, Providence, RI 02912
AB: Few students have the opportunity to witness volcanic eruptions first hand. Analog models of eruptive processes provide ways for students to apply basic physical principles when field observations are not feasible. We describe a safe simulation of violent volcanic explosions, one that can be carried out simply and easily as a demonstration for specialized volcanology classes, introductory classes, and science outreach programs. Volcanic eruptions are fundamentally gas-driven phenomena. Depressurization of volatiles dissolved in magma during ascent is the driving force behind most explosive eruptions. We have developed a demonstration whereby the instructor can initiate a gas-driven eruption, which produces a dramatic but safe explosion and eruptive column. First, one pours liquid nitrogen into a weighted, plastic soda bottle, which is then sealed and placed into a trashcan filled with water. As the liquid nitrogen boils, the pressure inside the bottle increases until the seal fails, resulting in an explosion. The expansive force propels a column of water vertically, to 10 or more meters. Students can operate the demonstration themselves and carry out a sequence of self-designed variations, changing the vent size and viscosity of the "magma", for instance. They can also vary the material used as "tephra", studying the effects of projectile density, column height, and wind direction on tephra distribution. The physical measurements that students collect, such as column height and tephra radius, can be used as the basis for problem sets that explore the dynamics of eruption columns. Possible calculations include ejection velocity, the pressure needed to propel the water column, and average vesicularity of the "magma". Students can then compare their results to observations from real volcanic eruptions. We find this to be an exceedingly effective demonstration of gas-driven liquid explosions and one that is safe if done properly. [NOTE: Please do NOT attempt this demonstration without full, detailed instructions and safety precautions, see website resource below].
UR: http://classes.colgate.edu/kharpp/Depth_Charge/default.htm
DE: 0810 Post-secondary education
DE: 0845 Instructional tools
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8428 Explosive volcanism
SC: Education and Human Resources [ED]
MN: Fall Meeting 2005