News & Views

Flowing water shapes most of Earth's canyons, obscuring the contributions of other erosional mechanisms. A comparison of adjacent canyons with and without wind shielding shows that wind can amplify canyon incision on windblown Earth and Mars.

Pinpointing when Earth's core formed depends on the extent of metal–silicate equilibration in the mantle. Vaporization and recondensation of impacting planetesimal cores during accretion may reconcile disparate lines of evidence.

Metals often accumulate in the crust beneath volcanoes. Laboratory experiments and observations reveal important roles for magmatic vapours and brines in transporting and concentrating the metals into deposits worth targeting for extraction.

The hydrology of the North American west looked very different at the Last Glacial Maximum to today. A model–data comparison suggests the observed precipitation patterns are best explained if the storm track was squeezed and steered by high-pressure systems.

Beneath the fresh and cold surface water in the Arctic Ocean resides more saline and warmer water of Atlantic origin. Pan-Arctic measurements of turbulent mixing suggest that tidal mixing is bringing up substantial amounts of heat in some areas.

Instrumental records have hinted that aerosol emissions may be shifting rainfall over Central America southwards. A 450-year-long precipitation reconstruction indicates that this shift began shortly after the Industrial Revolution.

The Witwatersrand Basin in South Africa contains extraordinary amounts of gold. Thermodynamic calculations suggest that the gold may have accumulated there in response to a perfect storm of conditions available only during the Archaean.

Boreal forest fires tend to be more intense and lethal in North America than Eurasia. Differences in tree species composition explain these differences in fire regime, and lead to contrasting feedbacks to climate.

The Sahara was more humid and habitable thousands of years ago. Reconstructions of North African hydroclimate show that the onset of aridity started in the north, with the monsoon rains weakening progressively later at lower latitudes.

In the first decades of the twentieth century, the Earth warmed rapidly. A coral-based climate proxy record of westerly winds over the equatorial Pacific suggests that wind strength and warming rate were linked, as they are today.

Soil contains aged organic carbon that can be hundreds or thousands of years old. Human disturbance in small and large watersheds is mobilizing some of this fossil carbon from soils to aquatic systems.

Carbon dioxide can stimulate photosynthesis in trees and increase their growth rates. A study of tree rings from three seasonal tropical forests shows no evidence of faster growth during 150 years of increasing atmospheric CO₂ concentrations.

A period of rapid warming about 55.5 million years ago was triggered by a massive release of carbon. The carbon isotope composition of soil nodules provides evidence for a smaller, but still important, carbon release prior to the main event.

The fate of water that enters the mantle within subducting slabs is unclear. Laboratory experiments indicate that subducted crust can transport large amounts of water into the deep Earth, and the lower mantle may become more hydrated over time.

Nitrous acid can initiate photochemical air pollution events, but it is not clear where it comes from. Laboratory experiments now suggest that surface-bound nitrite accumulated overnight can release nitrous acid during the daytime.