ANALOGUE MODELING OF INFLATION AND DEFLATION FEATURES IN THE TIETON ANDESITE LAVA FLOW

Analogue modeling of lava flow emplacement during the past several decades has provided insight into naturally occurring geodynamic processes that are difficult or impossible to directly observe. Ongoing field work has identified what is interpreted as inflation and deflation characteristics associated with effusive lava flows. The inflation and deflation of lava flows can provide a wide range of morphologic profiles due to crustal breakouts and flow passage “pileups”. In this study, we attempt to scale analogue lava flow models using paraffin wax to produce inflation and deflation features found in natural lava flows and compare these to those found in the Tieton andesite lava flow (1.6 Ma) erupted from the Bear Creek eruptive center. The viscosity of the paraffin wax, ranging from 50° C to +100° C, was measured using two methods: Stokes law and a Modular Compact Rheometer (MCR). The viscosities were calculated at 6.89 mPa s (60° C), 5.48 mPa s (70° C), 4.46 mPa s (80° C), 3.70 mPa s (90° C), and 3.12 mPa s (100° C). The effusion rate of the paraffin wax, heated to ~50° C, was emplaced through a 23 mm hose onto an inclined slope of increasing channel complexity to demonstrate the behavior of andesite lava flows under different conditions such as rough slope vs. smooth slope, and straight vs. sinuous channel. Different colored dye was used to differentiate layering in the wax to provide a clear visual representation of flow features. Experimental runs used the handheld camera as well as thermal capture of dynamic crustal development with fixed position thermocouples and a handheld FLIR imager. The different layering in the wax provides a clear visual of inflation and deflation characteristics. The final analogue model imitated the shape of the Tieton Andesite lava flow as well as the U-shaped valley it flowed into. At the 90° bend of the Tieton Andesite model, the paraffin wax inflated and piled up along the corner, subsequently causing a crustal breakout to occur past the bend. Following the breakout, the paraffin wax deflated at the 90° bend forming depression features near breakout zones. These findings support previous observed mechanisms for topographic depressions in flow fields. Additionally, the presence of topographic obstructions to downslope flow help identify characteristics found in ‘real-world” lava flows.