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The dynamics of dune evolution under bimodal wind regimes are poorly understood owing to a lack of long-term wind records and the limitations of most experimental set-ups. A 4-year landscape-scale experiment in the Tengger Desert, Mongolia, demonstrates that the orientation of oblique dune crests is controlled by the wind regime.
The 2011 eruption of a 20-km-high volcanic plume from Grímsvötn Volcano, Iceland, led to the closure of northern European airspace. Geodetic measurements from the volcano reveal a correlation between plume height, surface deformation and magma-chamber pressure, with a delay of an hour, implying that volcanic-plume behaviour can be predicted before eruption onset.
Chlorine radicals function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low. Measurements in the Arctic reveal high levels of molecular chlorine during the day, consistent with a photochemical source.
The global frequency of volcanic eruptions is inversely proportional to the volume of magma erupted in a single event. Numerical modelling of magma reservoirs evolving in Earth’s crust shows that frequent, small eruptions are triggered by injections of magma into the reservoir, but rare, giant supervolcano eruptions are triggered by magma buoyancy.
Supervolcano eruptions dwarf all historical eruptions, but their trigger mechanisms are unclear. Experimental measurements of magma density at high pressures and temperatures show that the buoyancy of magma alone can impose sufficient pressure at the roof of a supervolcano magma chamber to induce an eruption.