Presentation Information
[O09-P07]Development of a Volcanic Eruption Model Using Two-Component Polyurethane Foam: Reproducing Magma Intrusion, Stratospheric Umbrella Clouds, and Caldera Formation via Medium Density Control★Invited Papers
*Tatsuro Chiba1, Nanami Sugishita1, Koji Fujita1 (1.Asia Air Survey Co., Ltd.)
Keywords:
Two-component polyurethane foam,Medium density control,Eruption dynamics,Caldera formation and degassing
ABSTRACT
In school-level geoscience education, a significant challenge lies in providing students with an intuitive understanding of sub-surface, invisible phenomena and the vast spatio-temporal scales of volcanic dynamics. Traditional experimental methods using food materials or wax have struggled to simultaneously replicate the "expansion via vesiculation" and the "texture formation via solidification" of magma. This study establishes an experimental system that unifies the reproduction of volcanic processes—ranging from the formation of underground magma chambers to the development of umbrella clouds in Plinian eruptions, and even caldera collapse associated with degassing—by adjusting medium density and controlling bubble connectivity. Although this "Kitchen Volcanology" approach utilizes inexpensive, commercially available materials, we report on a methodology that faithfully reproduces fluid-dynamical and geological phenomena, alongside its physical interpretation.
1. Experimental Principle and Setup
This experiment utilizes two-component rigid polyurethane foam. Mixing the polyol (base resin) and isocyanate (hardener) triggers foaming within approximately one minute, resulting in a 20- to 30-fold expansion and subsequent solidification over several minutes. To simulate a volcanic conduit, a commercially available porcelain vase (ichirin-zashi) was used. The vase’s geometry—characterized by a wide body tapering toward the neck—is ideal for replicating the flow acceleration caused by convergence from a magma chamber into a conduit, effectively ejecting the foaming urethane. Other materials, such as plastic cups and buckets, were selected for their ease of procurement.
2. Reproducing Eruption Dynamics via Medium Density Control
Vases containing the mixed resins were placed at the bottom of media with varying densities (various powders) immediately after the reaction started. We compared how buoyancy, driven by apparent density differences, influenced magma behavior:(1) In Air: Since the apparent density of the urethane exceeds that of air, the foam immediately cascaded downward upon exiting the vase. It continued to foam while flowing, solidifying into a morphology closely resembling a lava flow.(2) Low-Density Medium (Styrofoam beads): Because the apparent densities of the urethane and the beads were comparable, the urethane lacked sufficient buoyancy. It grew as a spherical mass near the outlet, solidifying in a manner analogous to an intrusive body (magma chamber).(3) High-Density Medium (Bentonite/Cat litter): Due to the high apparent density of the bentonite particles, the urethane gained buoyancy and rose vertically by displacing the medium, eventually forming a dome-like mass on the surface.(4) Underwater: The vase was fixed at the bottom of a water-filled bucket. Due to the density contrast with water, the urethane rose rapidly in a narrow, vertical pipe-like flow. Upon reaching the water surface (a density interface), the ascent halted, and the material expanded horizontally into a disk shape. This process replicates the formation of an umbrella cloud when an eruption column reaches the stratosphere during a Plinian eruption.3. Bubble Coalescence and Caldera Formation via Wax Addition
Adding belt wax (a non-slip agent containing rosin) to the urethane mixture in a transparent plastic cup destabilizes the typical "closed-cell" structure, promoting bubble coalescence. Consequently, the enlarged, interconnected bubbles failed to support their own weight, leading to a structural collapse (subsidence). This phenomenon appears to simulate the depressurization of a magma chamber and subsequent caldera collapse following a large-scale eruption.
4. Educational Impact and Future Perspectives
This experiment provides a continuous demonstration of volcanic processes—foaming, ascent, intrusion, eruption, and collapse—through the dual lenses of physical density contrasts and chemical foaming/degassing. Furthermore, the solidified urethane can be easily sectioned with a bread knife for cross-sectional analysis or thin-slice observation, facilitating a deeper understanding of internal volcanic structures and texture formation. While blocking the vase outlet with a cork can simulate explosive eruptions and volcanic bomb generation, such procedures require ample space and rigorous safety management.
In school-level geoscience education, a significant challenge lies in providing students with an intuitive understanding of sub-surface, invisible phenomena and the vast spatio-temporal scales of volcanic dynamics. Traditional experimental methods using food materials or wax have struggled to simultaneously replicate the "expansion via vesiculation" and the "texture formation via solidification" of magma. This study establishes an experimental system that unifies the reproduction of volcanic processes—ranging from the formation of underground magma chambers to the development of umbrella clouds in Plinian eruptions, and even caldera collapse associated with degassing—by adjusting medium density and controlling bubble connectivity. Although this "Kitchen Volcanology" approach utilizes inexpensive, commercially available materials, we report on a methodology that faithfully reproduces fluid-dynamical and geological phenomena, alongside its physical interpretation.
1. Experimental Principle and Setup
This experiment utilizes two-component rigid polyurethane foam. Mixing the polyol (base resin) and isocyanate (hardener) triggers foaming within approximately one minute, resulting in a 20- to 30-fold expansion and subsequent solidification over several minutes. To simulate a volcanic conduit, a commercially available porcelain vase (ichirin-zashi) was used. The vase’s geometry—characterized by a wide body tapering toward the neck—is ideal for replicating the flow acceleration caused by convergence from a magma chamber into a conduit, effectively ejecting the foaming urethane. Other materials, such as plastic cups and buckets, were selected for their ease of procurement.
2. Reproducing Eruption Dynamics via Medium Density Control
Vases containing the mixed resins were placed at the bottom of media with varying densities (various powders) immediately after the reaction started. We compared how buoyancy, driven by apparent density differences, influenced magma behavior:(1) In Air: Since the apparent density of the urethane exceeds that of air, the foam immediately cascaded downward upon exiting the vase. It continued to foam while flowing, solidifying into a morphology closely resembling a lava flow.(2) Low-Density Medium (Styrofoam beads): Because the apparent densities of the urethane and the beads were comparable, the urethane lacked sufficient buoyancy. It grew as a spherical mass near the outlet, solidifying in a manner analogous to an intrusive body (magma chamber).(3) High-Density Medium (Bentonite/Cat litter): Due to the high apparent density of the bentonite particles, the urethane gained buoyancy and rose vertically by displacing the medium, eventually forming a dome-like mass on the surface.(4) Underwater: The vase was fixed at the bottom of a water-filled bucket. Due to the density contrast with water, the urethane rose rapidly in a narrow, vertical pipe-like flow. Upon reaching the water surface (a density interface), the ascent halted, and the material expanded horizontally into a disk shape. This process replicates the formation of an umbrella cloud when an eruption column reaches the stratosphere during a Plinian eruption.3. Bubble Coalescence and Caldera Formation via Wax Addition
Adding belt wax (a non-slip agent containing rosin) to the urethane mixture in a transparent plastic cup destabilizes the typical "closed-cell" structure, promoting bubble coalescence. Consequently, the enlarged, interconnected bubbles failed to support their own weight, leading to a structural collapse (subsidence). This phenomenon appears to simulate the depressurization of a magma chamber and subsequent caldera collapse following a large-scale eruption.
4. Educational Impact and Future Perspectives
This experiment provides a continuous demonstration of volcanic processes—foaming, ascent, intrusion, eruption, and collapse—through the dual lenses of physical density contrasts and chemical foaming/degassing. Furthermore, the solidified urethane can be easily sectioned with a bread knife for cross-sectional analysis or thin-slice observation, facilitating a deeper understanding of internal volcanic structures and texture formation. While blocking the vase outlet with a cork can simulate explosive eruptions and volcanic bomb generation, such procedures require ample space and rigorous safety management.