Volcanoes formed above the Hawaiian mantle plume exhibit a striking contrast in the geochemical characteristics of the lavas erupted at the northern Kea compared with the southern Loa volcanoes. Isotopic data show that these trends have persisted for more than five million years and may mirror compositional heterogeneities in the deep mantle. The image shows a solidified cracked lava flow in Hawaii Volcano National Park.

Review p831

COVER IMAGE: ISTOCKPHOTO.COM / SPRADA

COVER DESIGN: DAVID SHAND

Boninite lavas are erupted during the early stages of subduction, however they have previously been found only in the ancient geological record. Discovery of an active boninite eruption shows that abundant volatile gases derived from the subducting slab drive this violent eruptive activity, even in the deep sea. The image shows an explosive eruption of lava from Hades vent on West Mata volcano, 1,200 m below the sea surface in the southwest Pacific Ocean, captured by the remotely operated vehicle Jason.

Article p799; News & Views p737.

COVER IMAGE: NATIONAL DEEP SUBMERGENCE FACILITY, WOODS HOLE OCEANOGRAPHIC INSTITUTION

COVER DESIGN: DAVID SHAND

Microbes were thought to be the dominant reef constructors following the end-Permian mass extinction. Sponge-microbe reef deposits formed in the Early Triassic from the western United States suggest that instead, metazoan-reef building continued immediately following the extinction wherever marine conditions allowed. The image shows a large oncoid of about 2.5 cm in diameter, formed by bacterial growth during the Smithian, about 250  million years ago. It is embedded in a microbial and fenestral floatstone from the Mineral Mountains, Utah, which marks the base of the metazoan reefs.

Letter p693

COVER IMAGE: ARNAUD BRAYARD

COVER DESIGN: DAVID SHAND

Stretching of the continental crust can double its surface area, but it is unknown whether similar amounts of extension occur at depth. Seismic results from the central Basin and Range province, western USA, reveal a thick root of lithospheric mantle that has not been extended and indicates that crustal stretching is decoupled from extension at depth. The image shows badlands in Death Valley, California.

Letter p619

COVER IMAGE: IAN PARKER / EVANESCENT LIGHT PHOTOGRAPHY

COVER DESIGN: DAVID SHAND

Blooms of the nitrogen-fixing cyanobacterium Trichodesmium, which fuel primary production in tropical and subtropical waters, require large quantities of iron. Laboratory incubations suggest that Trichodesmium accelerates the dissolution of iron oxides and dust, increasing the rate of iron uptake. The image shows a puff-shaped Trichodesmium colony, originally from the Red Sea, as it captures desert dust and shuttles it to the centre of the colony in an experimental lab setting.

Letter p529

IMAGE: MAXIM RUBIN

COVER DESIGN: DAVID SHAND

The southern San Andreas fault terminates in a stepover zone — several small faults that separate major fault segments — beneath the Salton Sea. Analysis of movements on the stepover zone faults indicates that periodic flooding of the palaeo-Salton Sea during the late Holocene could have triggered earthquakes on the San Andreas fault. The image shows a large obsidian boulder that rests on the slope of Red Hill at the southeast edge of the Salton Sea, California, USA. The salt-encrusted shoreline of the Salton Sea is visible in the distance. Photo by Jenny E. Ross.

Article p486; News & Views p428

The origin of Titan's massive nitrogen atmosphere is largely unknown. Laser-gun experiments and numerical calculations suggest that the nitrogen could have been generated by conversion from ammonia during the period of Late Heavy Bombardment. The image shows Titan pictured by the Cassini spacecraft. Image courtesy of NASA/JPL/Space Science Institute.

Letter p359; News & Views p356

Submarine melting has been suggested as a trigger for the widespread acceleration of tidewater glaciers in Greenland. An analysis of oceanographic data from the fjord off Helheim Glacier, Greenland, suggests the presence of light Arctic and dense Atlantic waters in the fjord and that the melting circulation is more complex than thought. The image shows the Greenland ice sheet margin where it meets Sermilik Fjord, August 2009.

Photo © Nick Cobbing/Greenpeace.

Article p322

The timing and style of magmatism and extension during the final stages of continental breakup are uncertain. Analysis of ongoing rifting processes in Ethiopia reveals that after a protracted period of extension by magma intrusion, late-stage breakup is characterized by a final phase of plate stretching and voluminous basalt extrusion. The image shows a basaltic eruption from Erta Ale volcano located in the Danakil Depression, Ethiopia.

Photo by Lorraine Field, University of Bristol.

Letter p248

The extent of snow cover and sea ice in the Northern Hemisphere has declined since 1979, suggesting a positive feedback of surface reflectivity on climate. A synthesis of a variety of remote sensing and field measurements suggests that this albedo feedback from the Northern Hemisphere cryosphere falls between 0.3 and 1.1 W m−2 K−1. The image shows snow cover on the eastern Sierra Nevada, outside of the Sierra Nevada Aquatic Research Lab.

Letter p151

During the Eocene epoch, 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. The image shows open pit mining operations at Gold Quarry mine, Nevada (image courtesy of Jeremy Richards).

Article p122; News & Views p73

The origins of Alpine valleys are controversial. Topographic data from the Swiss Alps suggest that the valleys have been incised progressively during consecutive glacial–interglacial cycles. The image shows a railway viaduct across the Zügen gorge some 17 km southwest of Davos, in eastern Switzerland. The inner gorge is partly cut into carbonate rocks and more than 60 m deep at the location of the viaduct. Photo courtesy of O. Korup.

Article p62; News & Views p8