Magmatism is one of the dominant geological processes on terrestrial planets, and serves as a key interface between planetary interiors and exteriors. Over short timescales volcanic eruptions can generate regional and global perturbations in surface environments, and over long timescales magmatic processes control the structure and composition of planetary crusts. In my research I leverage field work, geochemical measurements, spacecraft data, and carefully constrained numerical models in order to probe the tectonic and environmental conditions that prevailed during critical periods in the history of the solar system.