News & Views in 2013

The classical view of fluvial sediment transport considers only physical interactions between the river flow and riverbed particles. Experiments and theory suggest that microbial biofilms reduce sediment mobility by binding many grains together.

The end of the Pleistocene epoch saw the extinction of large-bodied herbivores around the world. Numerical modelling suggests that continental-scale effects of this extinction on nutrient transport are ongoing.

Climate change is affecting the cryosphere from above. Geothermal heat flux from below is also contributing to conditions at the base of Greenland's ice sheet, which sits atop a lithosphere of variable thickness.

The Indonesian government ruled that the Lusi mud eruption was triggered by drilling and held an oil company responsible. Instead, a curved rock layer capping the mud reservoir may have amplified passing seismic waves and the trigger may have been natural.

Interactions between the ocean and atmosphere are complex. An analysis of satellite data from the Southern Ocean reveals a tight coupling of ocean and atmosphere on horizontal scales of around 100 km that modifies both near-surface winds and ocean circulation.

The extinction of megafauna in Australia roughly coincided with shifts in vegetation and fire regimes. Sediment geochemistry shows that the vegetation shift followed the extinction, indicating that the loss of browsers promoted fire and altered plant composition.

The East Antarctic ice sheet is believed to be Earth's most stable ice sheet. Changes in geochemical composition of offshore sediments suggest that its margin repeatedly retreated by at least 350–550 kilometres inland between 5.3 and 3.3 million years ago.

Subduction zone earthquakes cause the overriding plate to stretch and subside. Excessive subsidence of volcanoes during the large quakes in Chile in 2010 and Japan in 2011 highlight an unexpected response of volcanic areas to the sudden tectonic pull.

Mantle flow patterns may be reconstructed from mineral orientations. Experiments show that the high-pressure mineral post-perovskite can inherit texture from its lower-pressure counterpart, suggesting new ways of interpreting flow in the deepest mantle.

The daily vertical migration of small marine animals transfers organic carbon from the surface ocean to depth. An assessment of acoustic data reveals that the depth of migration is closely tied to subsurface oxygen levels throughout much of the global ocean.

The way in which seismic waves pass through the core suggests alignment of iron crystals within the solid inner core. Experiments indicate that iron at inner-core conditions may be weaker than thought and easily allow deformation of iron crystals.

Atmospheric aerosols affect climate by scattering and absorbing sunlight and by modifying clouds. Model simulations suggest that anthropogenic aerosols suppressed tropical storm activity over the Atlantic throughout much of the twentieth century.

Different measurements of inner core rotation have delivered inconsistent results. An analysis of seismic data provides a resolution of this discrepancy by suggesting decadal variations in inner core rotation rate.

The amount of carbon stored in the deep ocean varied over glacial–interglacial cycles. Southern Ocean sediments from the past 360,000 years show that carbon storage also fluctuated within glacial periods, in concert with the fertilization of the Southern Ocean by wind-borne dust.

High-temperature water–rock reactions produce large quantities of hydrogen, which must be transported to cooler settings to sustain life. Lower-temperature hydrogen generation could potentially support life in situ and free subsurface microbes from photosynthetic constraints.

Patches of deposits containing unusual mafic minerals are observed in and around some large lunar impact craters. Numerical simulations suggest that in the slowest of these impacts, asteroidal material, alien to the Moon, could have survived.

Sinking slabs of oceanic lithosphere often stagnate in Earth's mantle. Experiments show that common slab minerals transform to their high-pressure, high-density counterparts at very slow rates, thus keeping the slabs buoyant and impeding subduction.

Volcanic rocks erupted at mid-ocean ridges can record the temperature of the underlying mantle. Ancient crust in the Atlantic Ocean formed from anomalously hot mantle, possibly warmed by continental insulation before the opening of the ocean basin.

Antarctic climate has undergone substantial shifts in past decades, but whether these changes are unusual in the long term is unclear. Ice-core records suggest that some aspects of this variability are unique to the past two millennia.