Reviews & Analysis

Most of Earth's crust is created at mid-ocean ridges that are submerged deep beneath the oceans. Analyses of geodetic and seismic data from rare sections of ridges that are exposed on land in Iceland and the Afar region in east Africa demonstrate that rifting episodes at these sites operate with remarkably similar mechanisms.

The plausibility of the high end of global warming projections in recent assessments is a subject of debate. A study of multi-model climate simulations argues that we need to take the possibility of strong warming seriously.

A giant impact on the young proto-Earth is thought to explain the formation of the Moon. High-precision analysis of titanium isotopes in lunar rocks suggests that the Moon and Earth's mantle are more similar than existing models permit.

Glaciers supply downstream ecosystems with reactive dissolved organic carbon during periods of ice and snow melt. An analysis of glacier meltwaters in Alaska shows that anthropogenic aerosols fertilize these waters, raising questions about glacier greening.

The Arctic Ocean has become less saline, perhaps in response to climate change. Satellite and in situ observations reveal changes in the regional wind patterns that have re-routed freshwater and prevented it from leaving the Arctic Ocean in the past decades.

During the middle of the Cretaceous period, the polarity of Earth's magnetic field remained stable. A magnetic survey of oceanic crust formed during that time, however, suggests that the field intensity was surprisingly variable.

The configurations of ancient tectonic plates are difficult to reconstruct. Seismic images of deep subducted plates, combined with data from ancient volcanic arcs, help to derive a tectonic map of the Pacific Ocean as it was 200 million years ago.

Dune fields often exhibit complex patterns of vegetation and morphology over relatively short distances. An analysis of the White Sands dune field in New Mexico attributes the shift in dune form to the development of an internal boundary layer over the rough dune-field surface.

Atmospheric measurements reveal unexpectedly high concentrations of hydroxyl radicals over tropical forests. Incorporation of a new mechanism of isoprene oxidation into a chemistry model brings simulations into closer agreement with these observations.

The meridional overturning circulation of the ocean plays a central role in the climate and its variability. This Review of recent studies emphasizes the importance of wind-driven upwelling in the Southern Ocean for global ocean circulation.

Models predict that mercury undergoes rapid oxidation in the upper atmosphere. Aircraft measurements support this prediction and provide evidence for a previously unrecognized sink for stratospheric mercury.

The influence of trees and dead wood on river dynamics has long been overlooked. Recent work suggests that large wood pieces can stabilize the land surface, contributing to a large-wood cycle that profoundly affects floodplain morphology and ecology.

Toxic heavy metals can accumulate in Earth's near surface to form ore deposits. Experimental and direct measurements of ore fluids reveal the efficient mobilization and deposition of uranium, implying potentially rapid formation of economic-grade ore.

Throughout the Palaeozoic era, about 540 to 250 million years ago, plants colonized land and rapidly diversified. An analysis of the palaeontologic record shows that this diversification irrevocably altered the shape and form of fluvial systems.

Rivers draining the Himalaya provide vital resources for almost half of the world's population. A combined model–data analysis suggests that the contribution of groundwater to the annual water budget in the central Himalaya may be substantial.