Volume 8 Issue 3, March 2015

The status of sea floors is an important part of healthy marine ecosystems and intact coastlines. We need laws and a sea-floor management regime to make the exploitation of marine resources sustainable.

Ore bodies buried deep in Earth's crust could meet increasing global demands for metals, but mining them would be costly and could damage the environment. Reinventing an ancient technology for bioleaching metals could provide a solution.

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.

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 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.

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 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.

Faint M dwarf stars are the focus of searches for habitable planets. Numerical models suggest that changes in stellar luminosity lead to planets that are either too dry or too wet to be habitable in M dwarf systems.

The relative uncertainty of anthropogenic climate forcing has decreased in the past decade. A statistical model suggests that by 2030 this uncertainty will be halved, as CO₂ increasingly dominates over other human-made climate influences.

Short-lived halogens are produced naturally and anthropogenically, and are not governed by the Montreal Protocol. Like halocarbons, short-lived halogens destroy lower-stratospheric ozone, resulting in a net cooling effect since pre-industrial times.

Atlantic water brings heat to the subsurface Arctic Ocean. Pan-Arctic microstructure measurements of energy dissipation suggest that vertical mixing is substantial over the continental slopes, tidally induced, and insensitive to sea-ice cover.

The position of the intertropical convergence zone may be influenced by aerosols. A 450-year-long precipitation record from Belize confirms a southward shift associated with increasing anthropogenic aerosol emissions in the Northern Hemisphere.

The Last Glacial Maximum hydroclimate over western North America differed from the modern climate. A proxy-model comparison suggests that the glacial storm track was squeezed and steered by atmospheric high-pressure systems.

The Witwatersrand gold deposit is the largest in the world. Thermodynamic calculations show that such rich accumulations of gold could be linked to abundant volcanism, primitive life and the oxygen-free atmosphere of the Archaean.

The processes that create economic-grade accumulations of metals above magma chambers are unclear. High-temperature laboratory experiments show that rapid reactions between magmatic gases and Earth’s crust can trigger efficient metal deposition.

Copper ore deposits accumulate at relatively shallow depths in the crust, but it is unclear how the metal is transported. Laboratory experiments show that metals may hitch a ride on magma bubbles and float towards shallower depths.

Earth’s core exhibits similar elastic properties to rubber. Experiments show that a high-pressure phase of iron carbide modifies iron’s elastic properties under inner-core conditions, suggesting that carbon is the light element in the core.

The speed of seismic waves passing through the Earth’s inner core varies with direction. Analysis of earthquake seismic data suggests that this directional dependence differs between innermost and outer inner core.

Boreal forest wildfires in North America are more intense and destructive than in Eurasia. Differences in species-level adaptations to fire are primary drivers of these differences in fire regimes.

Most of the world’s copper comes from porphyry ore deposits. Laboratory experiments suggest that these deposits form in a two-stage process over thousands of years, from the interaction between sulphur-rich gases and metal-rich brines.

The demand for metals continues to grow, driven by the development of new technologies and the need for infrastructure to sustain ever-increasing populations. With improved understanding of the processes that transport and accumulate metals into economically viable deposits, we can target new places for exploration. In this Web Focus, we bring together a collection of primary research articles and opinion pieces that advance our understanding of how and where metals become enriched in Earth's crust and discuss strategies for their extraction.