Kinematics of lava flows based on fold analysis

A kinematic analysis of the mingling-folding structures occurring in a lava flow from Porri volcano (Southern Tyrrhenian Sea) has been performed in or der to estimate the flow kinematic parameters. Folds have resulted from the deformation of enclaves and banding structures, and consist of a single la yer of a crystal-rich andesitic magma hosted in a less competent basaltic m agma. Results of the analysis indicate that the flow kinematic vorticity in creases with the distance from the vent, whereas the ratio between pure she ar and simple shear strain decreases following a power law. Quantitative es timates of the kinematic parameters provide an opportunity to examine the d eformation behaviour of the lava flow. Near the vent, the lava is a non-ide al shear now; away from the vent, the lava is an ideal shear flow. Gravity- driven mechanisms control the relative contribution of pure and simple shea r to the bulk deformation.