Supereruption Research Articles

Dynamics of giant volcanic ash clouds from supervolcanic eruptions

The largest explosive volcanic eruptions that have occurred on Earth generated giant ash clouds from rising plumes that spread in the stratosphere around a height of neutral buoyancy, with estimated supply rates that are in the range 1011 to 1013 m3/s. These giant ash clouds are controlled by a balance between gravity and Coriolis forces, forming spinning bodies of nearly fixed proportions after a few hours and are initially insensitive to stratospheric winds. In contrast, volcanic plumes from eruptions with small to intermediate magnitude spread as inertial intrusions under the influence of stratospheric winds, with the Earth's rotation being unimportant. In the largest eruptions the giant spinning ash clouds typically develop diameters greater than 600 km and up to 6000 km in the most powerful super‐eruptions, thus explaining why areas of continental size can be covered with volcanic ash. The radial expansion and spinning velocities are calculated at tens of metres per second and increase with eruption intensity. Higher spreading velocities carry larger ash grain sizes to a given radius, so that grain size at a given distance from the source increases with eruption intensity, consistent with geological observations.

An AOGCM simulation of the climate response to a volcanic super-eruption

Volcanic ‘super-eruptions’ have been suggested to have significantly influenced the Earth’s climate, perhaps causing glaciations and impacting on the human population. Climatic changes following a hypothetical ‘super-eruption’ are simulated using a coupled atmosphere ocean general circulation model, incorporating scaled volcanic stratospheric aerosols. Assumptions are made about the stratospheric sulphate aerosol loading, size distribution, lifetime, chemical make up and spatial distribution. As this study is concentrating on the physical climatological impacts over long timescales, microphysics and chemical interactive processes are not simulated. Near-surface temperatures fall by as much as 10 K globally for a few months and a considerable deviation from normal temperatures continues for several decades. A warming pattern is evident over northern land masses during the winter due to increased longwave forcing and a positive AO mode. The overturning rate of the North Atlantic thermohaline circulation doubles in intensity. Snow and ice increases in extent to a maximum coverage of 35% of the Earth. Despite these and other impacts longer term climatic changes that could lead to a transition to a glaciation do not occur, for present day boundary conditions and one possible plausible aerosol loading.

Super-Eruptions and the Search for Extraterrestrial Intelligence (SETI)

Volcanic super-eruptions that produce >1000 km3 of ejected material and ≥ 1000 Mt (1015g) of stratospheric aerosols and sub-micron dust may be capable of creating global climatic disturbances sufficient to cause a severe setback or crash of modern civilization. Eruptions of similar magnitude are estimated to occur on average about every 50000 to 100000 years, which may be considerably more frequent than impacts by asteroids and comets that could cause similar climatic disasters. Prediction, prevention, and mitigation of global volcanic climatic disasters are potentially more difficult than planetary protection from large impactors, so that volcanism might provide an ultimate limit on the longevity of technological civilizations. If the lifetime of technological civilizations were limited to less than 50 000 years by volcanism, then the number of communicative civilizations in the Galaxy might be less than 1 per 10 million stars. Thus, super-eruptions on geologically active, habitable planets may strongly affect the prospects in radio telescopic SETI.

Earliest Acheulian Industry from Peninsular India

Decouverte d'un assemblage de 152 objets lithiques a Bori (Maharashtra, Inde) representant le plus ancien materiel connu de l'Acheuleen du subcontinent indien