Research articles

The southern San Andreas fault terminates in a stepover zone — several small faults that separate major fault segments — beneath the Salton Sea. Analysis of movements on the stepover zone faults indicates that periodic flooding of the palaeo-Salton Sea during the late Holocene could have triggered earthquakes on the San Andreas fault.

Cave deposits from China are commonly used to reconstruct the intensity of the East Asian monsoon precipitation. Numerical modelling indicates that these deposits may instead reflect changes in the strength of Indian monsoon precipitation and the isotopic signature of water vapour exported from India to China.

Sediments accumulated in a subduction trench are usually unconsolidated and impede the updip propagation of fault rupture during an earthquake. Seismic images of the southern Sumatra–Andaman trench reveal blocks of consolidated sediment that may have enabled fault rupture in 2004 to propagate up fault dip, thus further seaward, increasing the tsunami magnitude.

Afforestation, the conversion of croplands or marginal lands into forests, is considered one of the key climate-change mitigation strategies available to governments. Model simulations suggest that the temperature benefits of realistic afforestation efforts are marginal.

Hydrothermal vents along mid-ocean ridge systems host highly productive communities of microbes. Measurements along the Juan de Fuca ridge suggest that subsurface microbes consume hydrogen in low-temperature hydrothermal fluids, before discharge of these fluids at the sea floor.

Evapotranspiration of soil moisture can affect rainfall and the development of convective storms. Satellite observations of cloud and land-surface temperatures over the Sahel suggest that convective storms are more likely to form over strong mesoscale gradients in soil moisture.

V-shaped ridges of thickened oceanic crust above the Iceland plume are thought to record variations in the convection of the mantle below. Geochemical analyses of basalt samples taken from the ridges suggest the thickened crust formed as the result of blobs of hot mantle rising up in the underlying plume.

A brief period of warming 55.9 Myr ago has been attributed to the release of massive amounts of carbon. Geochemical and model data suggest the peak rate of carbon emission during this interval was relatively slow, and significantly lower than present-day levels of carbon emissions to the atmosphere.

Wetlands take up and store carbon, and release methane, through the decomposition of organic matter. Model simulations suggest that the areal extent of wetlands declines when permafrost thaws.

Feedbacks between soil moisture and precipitation are among the most important land–atmosphere interactions. An analysis of evaporative fluxes over North America suggests that the probability of afternoon rainfall in Mexico and the eastern United States is increased during periods of enhanced evaporation.

Erosion in the Washington Cascades Mountains was dominated by glacier activity until the end of the Last Glacial Maximum, when fluvial incision and mass wasting became the dominant drivers. An analysis of millennial-scale rates of denudation in the range suggest erosion is sensitive both to spatial variations in precipitation and inherited topography.

Photolysis of nitrous acid generates hydroxyl radicals — a key atmospheric oxidant. Measurements at a forest in Michigan suggest that sunlight-induced breakdown of nitric acid on the canopy surface serves as a significant source of nitrous acid to the overlying atmosphere.

Slow slip of the down-going plate at subduction zones can generate seismic tremor. Analysis of recent large tremor and slip episodes along the Cascadia subduction zone reveals tremor signals that reverse and rapidly migrate back along the previously ruptured fault, implying that the initial fault slip weakened the plate interface.

Mixing in the Southern Ocean plays an important part in large-scale ocean circulation and in climate. An analysis of high-resolution hydrographic profiles from the Argo float programme reveals that the seasonal cycle of mixing in the Southern Ocean is controlled by seasonal variations in the wind stress, in particular over flat topography.

The seismic hazard associated with individual faults can be assessed from the distribution of slip and the recurrence time of earthquakes. Analysis of the offsets of stream channels and terraces caused during five historical earthquakes on the Fuyun fault, China, reveals characteristic fault slip of about six metres for each event.

Carbonaceous minerals in 3.8-billion-year-old rocks from West Greenland have been used as evidence for early life on Earth. Geochemical analyses of similar carbon minerals in 3.75- to 4.2-billion-year-old rocks from Canada show that they can be derived from subsequent alteration more than a billion years after the initial formation.

The evolution of marine complex animals about 635 million years ago took place in relatively low-oxygen waters. An analysis of a low-oxygen, hypersaline lagoon suggests these early animals may have obtained both oxygen and food from widespread microbial mats.

Shallow earthquakes lead to the uplift of mountain ranges, but also trigger landslides that remove mass. An analysis of the 2008 Wenshuan earthquake suggests that more material was removed from the orogen by widespread landslides than was added by coseismic uplift.

The origin of Titan’s massive nitrogen atmosphere is largely unknown. Laser-gun experiments and numerical calculations suggest that the nitrogen could have been generated by conversion from ammonia during the period of Late Heavy Bombardment.

Hydrothermal vents emit metals such as iron to the ocean. A chemical analysis of hydrothermal fluids suggests that up to 10% of the iron is present as stable, iron-bearing nanoparticles.