Exploring the effects of a time- and space-dependent eruption efficiency on planetary evolution in mantle convection code StagYY.

Abstract

This project explored the effects of a time- and space-dependent eruption efficiency in planetary convection code StagYY. This has never been considered in a numerical simulation of global mantle convection before. The eruption efficiency gives the ratio of melt that erupts, the rest of the melt intrudes. The eruption efficiency in StagYY has thus far been treated as a constant in time and space. An equation was devised that describes how eruptive a system is, based on the main characteristics of crustal melt transport. These main characteristics are the amount of melt and the local stress state. In this article the effect of this equation is explored with the equation producing results in the background, but still keeping the eruption efficiency that is used constant. This is to find the effects of the equation without it affecting the results of the code. This has shown that the eruptivity of a system is mainly governed by the amount of melt, where the stress has smaller local effects. The eruptivity of a system is mainly governed by the yield stress, eruption efficiency and the viscosity. Parameters that govern the global temperature are less important for the eruptivity. If the eruption efficiency is fully time- and space-dependent the models behave like intrusive systems. The exceptions are resurfacing episodes, these moments are extrusive. Models that show mobile behaviour at almost all times in the planetary evolution will have an almost constant spatially averaged eruption efficiency.