Hot soft rock on the move: how lava redefines Earth's surface

Our planet is volcanically active, and as a result most of its surface is covered in lava. With about 1500 active volcanoes, 30 of which are typically erupting on any given day, hundreds of new lava flows are emplaced yearly, redefining large swaths of the terrestrial and submarine landscape.

Lava flow emplacement is largely controlled by its rheology. Far from being describable by a single number, lava’s complex multi-phase rheology evolves in space and time throughout emplacement, largely driven by cooling and crystallization. Upon eruption, 1200 °C lava can flow at speeds of up to 10 km/h (although velocities on the order of 1 km/h are more typical). Even long after the end of an eruption, and after having lost over half their initial heat content, lava flows can continue to inflate and/or to slowly creep for months, until they either cross the glass transition or meet their viscous death. The landscape reshaping is not yet complete at this point, as flows then typically deflate over many more years. Many dynamical regimes are thus needed to fully characterize how lava – a primary landscape reshaping agent – blankets and resurfaces our planet.

Laboratory experiments can provide valuable insights into lava rheology at different temperatures, crystallinities, and shear rates, matching its various emplacement stages. However, few laboratories worldwide have these measuring capabilities, and few scientists are trained in these experimental techniques. Nonetheless, the last decade has seen significant advancements in both instrumental precision and protocol development. As a result, the gap between laboratory and field measurements is shrinking, and the applicability of experimental measurements to real scenarios is growing, proving to be an invaluable asset in advancing our understanding.