Research articles

The Tibetan Plateau is expanding eastwards, but the modes of deformation are poorly understood. High-resolution seismic images from the region identify localized zones of weak crustal rocks as well as deep faults, implying that deformation occurs through a combination of crustal flow and movement of rigid blocks of crust.

At oceanic spreading centres, it is unclear whether plate motions drag the underlying mantle, or mantle flow pulls the overlying plates. Seismic imaging of a former speading centre in the Pacific Plate reveals strong seismic anisotropy that was generated by mantle flowing at speeds greater than plate motions, implying that mantle flow pulled this part of the plate.

Large subduction-zone earthquakes are thought to occur where the down-going and overriding tectonic plates are strongly locked. Analysis of geodetic and seismic data collected in the decade before the 2010 Chile earthquake shows that variations in pore-fluid pressure correlate with the degree of plate-interface locking, and may therefore control earthquake rupture.

As continents are stretched apart, deep rift valleys form and volcanoes can erupt both inside and outside of the valley. Numerical modelling suggests that gravitational unloading, caused by thinning of the stretched crust, can deflect rising magma towards the edges of the rift valley, causing off-rift eruptions.

The ability to predict surface winter climate in the Euro–Atlantic sector on seasonal timescales has been limited. Maximum covariance analysis now reveals that Arctic sea-ice variability represents a good predictor of the winter Euro–Atlantic climate, with as much as three months’ lead time.

The evolution of oxygenic photosynthesis should have occurred some time before the oxidation of Earth’s atmosphere 2.5 billion years ago. The molybdenum isotopic signature of shallow marine rocks that formed at least 2.95 billion years ago is consistent with deposition in waters that were receiving oxygen from photosynthesis at least half a billion years before the oxidation of the atmosphere.

The Indian summer monsoon is influenced by numerous factors, including aerosol-induced changes to clouds, surface and atmospheric heating, and atmospheric circulation. An analysis of satellite data and global climate model simulations suggests that dust aerosol levels over the Arabian Sea, West Asia and the Arabian Peninsula are positively correlated with the intensity of the Indian summer monsoon.

The tropical belt has expanded by several degrees latitude over the past 30 years, following an earlier period of contraction. Climate simulations indicate that tropical belt width is controlled by multidecadal sea surface temperature variability associated with the Pacific Decadal Oscillation and anthropogenic aerosols.

Observations of compressional structures on Mercury have fallen short of accommodating the global contraction that is required owing to cooling of the planet's interior. Mapping of folds and faults across Mercury's surface using MESSENGER spacecraft images reveals deformation consistent with a planet that has contracted radially as much as seven kilometres over its history.

Low levels of iron limit primary productivity across much of the Southern Ocean. Measurements of dissolved iron levels combined with hydrographic data suggest that much of the iron in the surface waters of the Southern Ocean is supplied by deep mixing during winter.

Fluctuations in North Atlantic climate and hydrography over the past 1,000 years are seemingly linked to changes in solar irradiance. Reconstructions of marine conditions compared with an analysis of climate model output indicate that low solar irradiance is associated with the development of a high-pressure system in the eastern basin that affects the dynamics of the subpolar gyre.

Ozone-depleting substances emitted through human activities cause large-scale damage to the stratospheric ozone layer, and influence global climate. An analysis of unpolluted air sampled from Tasmania and firn snow reveals the emergence of four new ozone-depleting substances in the atmosphere since the 1960s.

Following the Chicxulub impact, many foraminifera in near-surface waters perished, but bottom-dwelling species survived. Impact experiments suggest that sulphate in Chicxulubs target rocks was released as predominantly sulphur trioxide, which would have been converted to sulphuric acid in the atmosphere and swept down swiftly by larger particles, acidifying the ocean surface.

Regions of intense continental deformation, termed continental slivers, have been identified in Chile, Bolivia and Ecuador. Analyses of GPS data now identify another large sliver in Peru, the Inca Sliver, that is moving away from a neighbouring sliver in Ecuador—implying that moving continental slivers control the deformation of almost the entire Andean mountain range.

During the Last Glacial Maximum, tropical glacier snowlines were lower than expected, based on estimates of tropical sea surface temperatures. Sea surface temperature reconstructions suggest the Indo-Pacific warm pool was cooler than previously thought; these temperatures and convective mixing processes can explain snowline altitude in this region.

Humic substances make up a significant fraction of the natural organic matter in terrestrial and aquatic environments. Laboratory experiments suggest that humic substances serve as fully regenerable electron acceptors in recurrently anoxic environments such as peatlands.

Breaking waves on the ocean surface generate air bubbles that yield sea spray aerosols when released to the atmosphere. Measurements of sea spray aerosols in the North Atlantic Ocean and the coastal waters of California suggest that the surface water organic carbon reservoir is responsible for the organic carbon enrichment of freshly emitted sea spray aerosol.

Global mean surface and tropospheric temperatures have shown slower warming since 1998 than found in climate model simulations. A detailed analysis of observations and climate model simulations suggests that the observed influence of volcanic eruptions on tropospheric temperature has been significant, and that the discrepancy between climate simulations and observations is reduced by up to 15% when twenty-first century volcanic eruptions are accounted for in the models.

The oldest minerals on Earth are thought to have formed in the Hadean eon, but the reliability of the dates has been questioned. Atom-probe tomography of an ancient zircon confirms that the mineral formed about 4.4 billion years ago, implying that any mixing event of the silicate Earth occurred before that time.

At least two-thirds of marine genera died out during the end-Permian mass extinction about 252 million years ago. An analysis of extinct and surviving taxa shows no substantial loss in global functional diversity, although there were significant losses in some settings such as tropical reefs.