Reviews & Analysis

During an earthquake, friction is a key control on the initiation, propagation and termination of fault motion. Laboratory experiments that use variable slip rates suggest that friction evolves in a more complex fashion than generally assumed.

Forest fires convert a small portion of burning vegetation into charred solid residues such as charcoal. A survey of Scandinavian forest soils reveals that charcoal has a highly patchy distribution, and a shorter-than-expected lifetime.

Conflicting proxies for the size of early Antarctic ice sheets have been puzzling. A reconstruction of West Antarctica's past elevation suggests that the disagreement stems from an underestimation of Antarctica's surface area above sea level.

Many of the world's deltas are densely populated and intensively farmed. An assessment of recent publications indicates that the majority of these deltas have been subject to intense flooding over the past decade, and that this threat will grow as global sea-level rises and as the deltas subside.

As the Earth warms, the overturning circulation of the upper atmosphere is projected to speed up. Model simulations suggest that this will increase the flux of ozone from the stratosphere to the troposphere, and alter surface levels of ultraviolet radiation.

Purported 3,465-million-year-old microfossils from Australia have been the subject of considerable debate. A method to distinguish between pristine fossils, mineral artefacts and subsequent microbial contamination will aid the search for ancient biogenic material.

The fate of sinking particulate organic matter in the world ocean is a key source of uncertainty in the global carbon cycle. Model simulations suggest that atmospheric carbon dioxide concentrations depend critically on the depths that these particles typically reach.

Titan's surface is covered by vast fields of linear dunes, probably composed of organic sand-sized particles. The study of linear dunes in China suggests that sediment cohesiveness can be as important as wind direction in the creation of these dune forms.

The Pacific and Australian plates collide and interact in complex ways around New Zealand. Electrical resistivity data reveal that subduction-zone fluids exert an important influence on deformation in the region.

Slab fluids drive mantle melting and return ocean water to the Earth's surface through arc volcanism. New ways of estimating the temperature of slab fluids indicate relatively hot conditions, and hint at a shallow and fast return path for ocean water.

The Salton Sea is located in a sedimentary basin at the southern termination of the San Andreas fault. High-resolution seismic data indicate that the basin formed and grew by active subsidence at its southern end.

Modern terrestrial microbes have shown a puzzling ability to use reduced forms of phosphorus not commonly found on Earth. An examination of glasses formed in the ground by lightning suggests that lightning strikes can generate these phosphorus species.

Fossils from southern China provide evidence for a mass extinction during middle Permian time, 260 million years ago. The close association of this event with an outpouring of lava, initially into the sea, indicates that explosive volcanism may have been the cause.

Science and society are faced with two challenges that are inextricably linked: fossil-fuel energy dependence and rising levels of atmospheric carbon dioxide. Coupling of noble gas and carbon chemistry provides an innovative approach to understanding the deep terrestrial carbon cycle.

Global warming 55 million years ago was accompanied by a massive injection of carbon into the ocean-atmosphere system, but the resulting climatic warming was much greater than expected from the modelled rise in atmospheric carbon dioxide alone.

It is unclear whether the modern processes of mercury cycling — such as mercury deposition in polar regions — operated before anthropogenic emissions. Ice-core records from Antarctica now reveal strikingly high mercury concentrations during the coldest glacial periods.