Magma supply from the lower crust is often proposed as a trigger mechanism for volcanic
eruptions. The timescales over which magma can be transported from the deepest parts of
volcanic systems are, however, poorly constrained. This uncertainty poses problems for the
construction of physical models and for assessment of volcanic hazards. Here, we combined
geothermobarometry with Bayesian inversion diffusion chronometry on primitive olivine
crystals from the Borgarhraun eruption, northern Iceland. We find that magma took about 10 …