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The world's largest freshwater resource is groundwater. A review of our understanding of groundwater depletion suggests that although the problem is global, solutions must be adapted to specific regional requirements at the aquifer scale.
Magma erupted at subduction-zone volcanoes contains mantle rocks and a mixture of fluids and sediments derived from the subducted slab. A synthesis of work over past years provides an integrated physico-chemical framework for subduction zones with mixing at the slab–mantle interface and transport towards the surface volcanoes by buoyant diapirs.
During periods of glaciation, the Northern Hemisphere was swathed by large ice sheets. A review of ice-sheet retreat during the last two deglaciations shows that land-based ice sheets responded rapidly to rising summer insolation, whereas marine-based ice sheets underwent a delayed, but more abrupt, response.
The geomagnetic field varies on a wide range of timescales. A review of emerging research suggests that field variations on the order of tens of millions of years may be linked to changes in heat flow across the core–mantle boundary.
Over 90% of species were lost during the end-Permian mass extinction. A review of the fossil record shows that the rate of recovery was highly variable between different groups of organisms as a result of complex biotic interactions and repeated environmental perturbations.
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 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.
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.
