Volume 4 Issue 2, February 2011

The contribution of glaciers and ice caps to global sea-level rise is uncertain: they are incompletely counted and the calculation is challenging. A new estimate from the best available data suggests a contribution of about 12 cm by 2100.

How the giant sediment-hosted gold deposits of Nevada were formed is disputed. A model linking regional tectonics with magma emplacement and fluid generation at depth suggests that these deposits result from an optimal coincidence of processes.

The origin of water in the Earth–Moon system is an open question. Geochemical analysis of the rocks retrieved by the Apollo missions show that lunar and terrestrial water are isotopically distinct, suggesting acquisition after the Moon's formation.

Mineral dust and biological particles of terrestrial origin initiate ice formation in the atmosphere. Laboratory experiments suggest that ocean diatoms are another potential source of ice nuclei in clouds.

The mechanisms that govern the growth of debris flows are largely unclear, hampering efforts to assess natural hazards in landslide-prone areas. Experiments suggest that high bed-water content increases flow velocity and mass entrainment in landslides.

Water has been found in many lunar rock samples, but its sources are unknown. Isotopic analyses of Apollo samples of lunar mare basalts and highlands rocks suggest that a significant volume of water was delivered to the Moon by comets shortly after its formation by giant impact.

Following a hypothesized complete cessation of carbon dioxide emissions, global climate models simulate approximately constant global mean temperatures for centuries. Long-term simulations with the Canadian Earth System Model suggest that, on these timescales, regional changes in temperature and precipitation are nevertheless significant, and that Southern Ocean warming at intermediate depths could affect the stability of Antarctic ice.

Biogenic aerosol particles of terrestrial origin, including bacteria and pollen, trigger ice formation in the atmosphere. Laboratory experiments reveal that biogenic particles of marine origin also initiate ice formation under typical tropospheric conditions.

The contribution to sea-level rise from mountain glaciers and ice caps has grown over the past decades. A projection of their melting during the twenty-first century based on temperature and precipitation projections from ten climate models suggests that by 2100 these glaciers will lose about 21% of their total global volume.

Manganese oxide minerals control numerous environmental processes, including the fate of contaminants. Laboratory experiments with a common species of marine bacteria reveal that bacterially generated superoxide can oxidize manganese ions, generating manganese oxides.

The impact of external influences on European temperatures before 1900 has been thought to be negligible. An analysis of reconstructions of seasonal European land temperatures and simulations from three global climate models instead suggests that external forcing is responsible for a best guess of 75% of the observed winter warming since the late seventeenth century.

The eruption of the Siberian Trap flood basalts resulted in the heating and combustion of coals and organic-rich sediments at the time of the Permian mass extinction. The presence of char in distant lake sediments linked to the eruption suggests that fly ash could have been generated by the coal combustion, and then dispersed globally, creating toxic marine conditions.

The amount of fluid delivered to subduction zones by the oceanic crust and penetrating sea water is not matched by that leaving through volcanic emissions or transfer to the deep mantle. Electromagnetic images of the Costa Rican subduction zone reveal an extra reservoir in the crust that may account for some of the missing fluid.

Magma transports metals to the Earth’s surface to form ore deposits, but only sulphide-undersaturated magmas were thought to be capable of generating large amounts of ore. Laboratory experiments indicate that large volumes of gold ore can also be generated by sulphide-saturated magma, if the redox conditions of the magma are suitable.

The mechanisms by which debris flows acquire mass and momentum as they entrain material are unclear. Large-scale experiments suggest that the pore pressure of wet bed sediment increases as the flow moves over the bed, leading to reduced friction and progressive scouring of the base.

During the Eocene, profuse magmatism and hydrothermal activity in the Great Basin of western North America produced Earth’s second largest concentration of gold in Nevada. An integration of mineral analyses, experimental data and age and isotope data suggests a magmatic source for these deposits.

Richard Iverson and colleagues made enough of a din to scare the bears when sending large amounts of debris down a 95-m-long flume to find out what difference wet sediments make to an avalanche.