Reviews & Analysis

The timing and nature of changes in the chemistry of the early oceans are intensely debated. Geochemical analyses show that a prominent transition to sulphidic marine conditions 1.8 billion years ago may have been restricted to near-shore environments.

The mechanics of slip on faults in the Earth's crust are still unclear. Field observations from New Zealand show that movement can occur where — according to conventional assumptions of fault strength — it should not be possible.

The northern plains of Mars are thought to have harboured an ocean more than 3.6 billion years ago. Delta deposits and river-valley termini ring the proposed seabed and define an equipotential palaeoshoreline.

Most of the oceanic crust has a simple layered structure. The discovery that slow-spreading ridges exhibit a comparatively complex crustal structure and some of the largest extensional faults on Earth is leading to the recognition of a new mode of seafloor spreading.

Direct evidence for the role of volatiles in magmatic ore formation has been elusive. Magma degassing at Merapi volcano in Indonesia is found to be directly linked to the selective leaching of metals from sulphide melts that ultimately form ore deposits.

Pine Island Glacier on West Antarctica's Amundsen Sea coast has experienced accelerating retreat over the past few decades. Oceanographic observations under the associated ice shelf show how changes in water flow and ice-cavity geometry have contributed to ice melting.

The Triassic/Jurassic boundary was marked by widespread environmental changes, including greenhouse warming. Palaeoecological reconstructions from East Greenland reveal a dramatic rise in fire activity, driven by vegetation shifts and climate change.

Low atmospheric carbon dioxide concentrations during glacial periods must have been accompanied by changes in surface-ocean carbonate chemistry. But it is unclear whether concurrent changes in the deep sea contributed to the glacial carbon dioxide decline.

The ocean's nitrogen budget has escaped quantification. A modelling study shows how a small shift in the nitrate-to-phosphate uptake ratio of phytoplankton has a large effect on calculated nitrogen fixation rates.

Greenland's ice sheet does not look like an alpine glacier. However, it behaves like one in the way its meltwater lubricates basal motion, suggesting that projections of sea-level change will require unified knowledge of basal processes in glaciers and ice sheets.

The duration of Earth's creation remains unknown. Elegant modelling of the Earth's core formation reaffirms that the bulk of accretion occurred within a few tens of millions of years, but another 100 million years or so were needed to finish the job.

The rate at which new marine animals evolve has varied through time, but the factors that ultimately drive these fluctuations are unclear. A statistical analysis shows that global changes in abiotic factors play an important role.

The El Niño–Southern Oscillation is a naturally occurring fluctuation that originates in the tropical Pacific region and affects the lives of millions of people worldwide. An overview of relevant research suggests that progress in our understanding of the impact of climate change on many of the processes that contribute to El Niño variability is considerable, but projections for the phenomenon itself are not yet possible.

The organic matter stored in frozen Arctic soils could release significant quantities of carbon dioxide and methane on thawing. Now, laboratory experiments show that re-wetting of previously thawed permafrost could increase nitrous oxide production by 20-fold.

Increasing temperatures stimulate the decomposition of soil organic matter in the short term. But a shift in microbial carbon allocation could mitigate this response over longer periods of time.

The amount of pore space in most unweathered granite is too small to support a plant-based ecosystem. But porosity grows as intact rock interacts with surface waters beneath the soil.