Volume 8 Issue 4, April 2015

The impact of a volcanic eruption depends on more than just its size. We need more interdisciplinary research to understand the global societal consequences of past and future volcanic eruptions.

The 1815 eruption of Tambora caused an unusually cold summer in much of Europe in 1816. The extreme weather led to poor harvests and malnutrition, but also demonstrated the capability of humans to adapt and help others in worse conditions.

200 years after the eruption of Mount Tambora, the eruption volume remains poorly known, as is true for other volcanic eruptions over past millennia. We need better records of size and occurrence if we are to predict future large eruptions more accurately.

Ice shelves in West Antarctica have been shown to melt where warm circumpolar deep water enters a sub-shelf cavity. A bathymetric reconstruction of Totten Glacier in East Antarctica suggests that the same process may be at work there.

Flowing water shapes most of Earth's canyons, obscuring the contributions of other erosional mechanisms. A comparison of adjacent canyons with and without wind shielding shows that wind can amplify canyon incision on windblown Earth and Mars.

Subducting oceanic crust is sometimes observed to stagnate in the lower mantle. Laboratory experiments show that high pressures in the deep Earth may strengthen mantle rocks, increasing their viscosity and halting the sinking slabs.

Pinpointing when Earth's core formed depends on the extent of metal–silicate equilibration in the mantle. Vaporization and recondensation of impacting planetesimal cores during accretion may reconcile disparate lines of evidence.

Deep abyssal clay sediments in organic-poor regions of the ocean present challenging conditions for life. Techniques for identifying cells at extremely low concentrations demonstrate that aerobic microbes are found throughout these deep clays in as much of 37% of the global ocean.

Our understanding of the interactions between clouds, circulation and climate is limited. Four central research questions — now tractable through advances in models, concepts and observations — are proposed to accelerate future progress.

Differentiated planetesimals may have delivered iron-rich material to Earth in giant impacts at the end of accretion. Impact experiments suggest that the planetesimals’ iron cores vaporized, aiding dispersal and mixing into Earth’s mantle.

Some biological particles act as ice nuclei in the atmosphere, affecting clouds and precipitation. Cloud-chamber experiments demonstrate that cellulose particles can act as efficient ice-nucleating particles in supercooled clouds.

The El Niño/Southern Oscillation modulates global weather and climate. Analyses of large-scale environmental indices show that it also affects the frequency of tornado and hail events in the central United States, which may help with predictability.

Droughts can cause dry-season productivity to decline in tropical forests. This decline occurs when precipitation is below 2,000 mm yr⁻¹, resulting in insufficient subsurface water storage to maintain constant production through the dry season.

Arsenic in aquifers is transformed by biological and abiotic reactions. Field measurements and laboratory experiments suggest that the microbial methylation of arsenic contributes to subsurface arsenic cycling.

Totten Glacier has the largest thinning rate in East Antarctica. A derivation of the sea floor bathymetry reveals entrances to the ice cavity beneath the glacier that could allow deep warm water to enter and enhance basal melting.

The depth of oxygen penetration and microbial activity in marine sediments varies by region. Sediment cores from the South Pacific Gyre host oxygen and aerobic microbial communities to at least 75 metres below the sea floor.

Water is considered the primary agent that erodes and shapes bedrock canyons. Analyses of canyon morphology in the central Andes suggest that abrasion by wind can amplify canyon incision and reshape canyons on Earth—and possibly on Mars.

Subducting slabs can stagnate in the lower mantle. High-pressure laboratory experiments show that the viscosity of a dominant mantle phase increases dramatically at shallow lower-mantle depths, which could cause the slabs to halt their descent.

Precipitation patterns in the western Pacific changed at the onset of the Little Ice Age. A synthesis of precipitation reconstructions suggests that this change resulted from a contraction of the intertropical convergence zone.

The origin of continental crust is unclear. Geochemical and geophysical analyses of the Central American land bridge show that continental crust began to form there when enriched oceanic crust created above the Galápagos plume was subducted.

In April 1815, the eruption of Tambora VolcaNo. in Indonesia — one of the largest in recorded history — blasted ash and gases into the atmosphere purportedly causing widespread cooling and crop failure. 200 years on, the dynamics and effects of the Tambora eruption continue to fascinate and inform understanding of other giant eruptions in the past and future. In this Web Focus, we bring together a collection of opinion pieces that discuss current understanding of the Tambora event and other giant eruptions, and their impacts on society and the environment.