Articles in 2009

Interactions between microbes and minerals are evident in modern global elemental cycles. Relationships between minerals in Cambrian mudstones indicate that such interactions may have released otherwise unavailable, mineral-bound iron and silica into the ancient oceans.

Under drought conditions, biomass burning in Indonesia is a disproportionate contributor to the global carbon dioxide emissions from such events. An analysis of Indonesian records of large fires shows that their occurrence is linked to land use and population dynamics, and that the Indian Ocean climate and El Niño both have an equally important influence.

The timing and mechanisms of the transition from a glacial to an interglacial state are controversial. An analysis of Antarctic ice-core records indicates that glacial terminations may begin as millennial-scale warmings in the southern hemisphere that, unlike previous events, are not reversed by abrupt warming in the northern hemisphere.

The variations of tropical precipitation are antiphased between the hemispheres on orbital timescales. A comparison between a speleothem record of precipitation in northeast Brazil and rainfall reconstructions from the rest of tropical South America shows that a similar antiphasing operated in the same hemisphere during the Holocene.

The Younger Dryas event was a brief return to cold conditions before the onset of interglacial warmth. An analysis of sediment records from Lake Kråkenes in Norway and the Nordic Seas shows that during the late Younger Dryas, Northern Europe underwent rapidly oscillating climate conditions, possibly related to the break-up of Nordic sea-ice.

Nitrous oxide is a potent greenhouse gas whose concentration is increasing in the atmosphere; the highest emissions have been observed from agricultural and tropical soils. Now, measurements in subarctic East European tundra show that bare surfaces on permafrost peatlands, known as peat circles, release large quantities of nitrous oxide.

Although a number of hypotheses have been put forward to explain the sulphate deposits discovered by the Opportunity rover at Meridiani Planum, Mars, the sedimentary layers remain enigmatic. A re-analysis of the chemistry, sedimentology and geology of the deposits suggests they formed through a reworking of the sublimation residue from a large-scale deposit of ice and dust.

Hydrothermal vents release significant quantities of dissolved iron into the oceans. Spectromicroscopic examination of a hydrothermal plume suggests that carbon-rich matrices protect this iron from oxidation and precipitation.

The Charles Darwin bicentennial celebrates the man who recognized natural selection and changed the world's views on evolution. However, his contributions to geology should not be overlooked.

Ice ages in the North Pacific Ocean and the Southern Ocean were marked by low productivity. Accumulating evidence indicates that strong stratification restricted the supply of nutrients from the deep ocean to the algae of the sunlit surface in these regions.

Competition from the New World, a changing climate and technological advances have threatened the Burgundian notion that the quality of wine depends on regional geography and culture. Only flexibility can keep the concept of terroir alive.

Within just three years, a 2,000-km stretch of the plate boundary tracing the Indonesian archipelago slipped in four earthquakes. Studies of past and present seismic activity in the region show a complex, but organized pattern of earthquake supercycles, the latest of which has not been completed.

The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground.

Surface ozone levels are expected to be high in polluted regions during summer months. Observations from Wyoming in February 2008 indicate that equally high concentrations of ozone can be produced during winter.

The exact mechanism used by microorganisms to produce the neurotoxin methyl mercury is unclear. The latest laboratory studies point to the amino acid cysteine as an important aid for the uptake of inorganic mercury and its transformation to methyl mercury in Geobacter sulfurreducens.

Groundwater seepage is expected to affect channel features, but its role remains controversial. Two linear response relationships that describe channel evolution from groundwater flux are sufficient to characterize seepage-driven channel networks, linking the dynamics of channel growth to channel morphology.