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Editorials

Big, old and complicated p665

doi:10.1038/ngeo654

Earth scientists learn to approach scientific questions from a unique perspective — one that Charles Darwin shared.


Fake plastic trees p665

doi:10.1038/ngeo655

Greenhouse-gas emissions keep rising, despite all efforts at regulation and international agreement. Geoengineering could provide a back-up plan.


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Commentary

Man, myth, geologist pp666 - 667

Mott T. Greene

doi:10.1038/ngeo646

Charles Darwin became the founder and mythic hero of modern evolutionary biology with the publication of his work On the Origin of Species 150 years ago. The book bears the signature of a geological thinker who had turned to a faster-moving discipline.


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Books and Arts

As Darwin wrote p668

Alicia Newton reviews Charles Darwin's Notebooks From the Voyage of the Beagle by Gordon Chancellor & John van Wyhe

doi:10.1038/ngeo648


Exhibition: Darwin on the rocks pp668 - 669

doi:10.1038/ngeo649


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Research Highlights


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News and Views

Tectonics: Antarctica sinking pp671 - 672

Michael Studinger & Peter Barrett

doi:10.1038/ngeo644

Conflicting proxies for the size of early Antarctic ice sheets have been puzzling. A reconstruction of West Antarctica's past elevation suggests that the disagreement stems from an underestimation of Antarctica's surface area above sea level.

Subject Category: Structural geology, tectonics and geodynamics


Palaeoclimate: Potomac paradise p672

Alicia Newton

doi:10.1038/ngeo651


Palaeomagnetism: In GAD we trust pp673 - 674

Joseph G. Meert

doi:10.1038/ngeo635

Palaeomagnetists' basic assumption that Earth's magnetic field is a GAD, that is, a geocentric axial dipole, has been challenged by anomalous magnetic data from ancient Canadian basalts. At a closer look, fast continental drift could explain this anomaly.

Subject Category: Geomagnetism, palaeomagnetism and core processes

See also: Letter by Swanson-Hysell et al.


Biogeochemistry: Fire's black legacy pp674 - 675

Caroline M. Preston

doi:10.1038/ngeo642

Forest fires convert a small portion of burning vegetation into charred solid residues such as charcoal. A survey of Scandinavian forest soils reveals that charcoal has a highly patchy distribution, and a shorter-than-expected lifetime.

Subject Category: Biogeochemistry

See also: Letter by Ohlson et al.


Seismology: The roller coaster of fault friction pp676 - 677

Nadia Lapusta

doi:10.1038/ngeo645

During an earthquake, friction is a key control on the initiation, propagation and termination of fault motion. Laboratory experiments that use variable slip rates suggest that friction evolves in a more complex fashion than generally assumed.

Subject Category: Seismology

See also: Letter by Sone & Shimamoto


Atmospheric science: Putting the wind up ozone pp677 - 679

David S. Stevenson

doi:10.1038/ngeo634

As the Earth warms, the overturning circulation of the upper atmosphere is projected to speed up. Model simulations suggest that this will increase the flux of ozone from the stratosphere to the troposphere, and alter surface levels of ultraviolet radiation.

Subject Category: Atmospheric science

See also: Letter by Hegglin & Shepherd


Paul G. Silver: Earth deformation, writ large p679

Sean C. Solomon

doi:10.1038/ngeo650


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Progress Article

Sinking deltas due to human activities pp681 - 686

James P. M. Syvitski, Albert J. Kettner, Irina Overeem, Eric W. H. Hutton, Mark T. Hannon, G. Robert Brakenridge, John Day, Charles Vörösmarty, Yoshiki Saito, Liviu Giosan & Robert J. Nicholls

doi:10.1038/ngeo629

Many of the world's deltas are densely populated and intensively farmed. An assessment of recent publications indicates that the majority of these deltas have been subject to intense flooding over the past decade, and that this threat will grow as global sea-level rises and as the deltas subside.

Subject Category: Geomorphology


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Letters

Large climate-induced changes in ultraviolet index and stratosphere-to-troposphere ozone flux pp687 - 691

Michaela I. Hegglin & Theodore G. Shepherd

doi:10.1038/ngeo604

Now that stratospheric ozone depletion has been controlled by the Montreal Protocol, interest has turned to the effects of climate change on the ozone layer. An atmospheric chemistry model suggests that climate change will increase the stratosphere-to-troposphere ozone flux by 23% globally between 1965 and 2095, altering the amount of ultraviolet radiation reaching Earth's surface.

Subject Category: Atmospheric science

See also: News and Views by Stevenson


The charcoal carbon pool in boreal forest soils pp692 - 695

Mikael Ohlson, Barbro Dahlberg, Tonje Økland, Kendrick J. Brown & Rune Halvorsen

doi:10.1038/ngeo617

Forest fires release significant amounts of carbon dioxide into the atmosphere, but also convert a fraction of the burning vegetation to charred black carbon. Examination of 845 soil samples in Scandinavian forests shows that the charcoal content of boreal soils is highly variable, and more susceptible to degradation than has been thought.

Subject Category: Biogeochemistry

See also: News and Views by Preston


A microbial source of phosphonates in oligotrophic marine systems pp696 - 699

Sonya T. Dyhrman, Claudia R. Benitez-Nelson, Elizabeth D. Orchard, Sheean T. Haley & Perry J. Pellechia

doi:10.1038/ngeo639

Phosphonates, compounds with a carbon–phosphorus bond, are a key component of the marine-dissolved organic phosphorus pool. Nuclear magnetic resonance spectroscopy measurements suggest that the cyanobacteria Trichodesmium is a significant source of phosphonates in nutrient-poor regions of the ocean.

Subject Categories: Biogeochemistry | Oceanography


Virtual seismometers in the subsurface of the Earth from seismic interferometry pp700 - 704

Andrew Curtis, Heather Nicolson, David Halliday, Jeannot Trampert & Brian Baptie

doi:10.1038/ngeo615

Earthquakes often occur in areas that lack an array of seismometers, resulting in a scarcity of local measurements from some regions of great geological interest. In such regions, some earthquakes themselves may be turned into virtual seismometers that are capable of measuring strain caused by passing waves from other earthquakes.

Subject Category: Seismology


Frictional resistance of faults during accelerating and decelerating earthquake slip pp705 - 708

Hiroki Sone & Toshihiko Shimamoto

doi:10.1038/ngeo637

The dynamic friction along faults controls earthquake ruptures in the crust, but many previous studies have quantified this value only for constant slip rates. Experiments accounting for the more realistic condition of changing slip rates suggest that faults undergo a sequence of strengthening, weakening and healing during acceleration and deceleration of slip.

Subject Categories: Seismology | Structural geology, tectonics and geodynamics

See also: News and Views by Lapusta


Rock pulverization at high strain rate near the San Andreas fault pp709 - 712

Mai-Linh Doan & Gérard Gary

doi:10.1038/ngeo640

Rocks near the San Andreas fault are pervasively crushed at distances of up to 400 m from its core. Laboratory experiments and calculations suggest that the rocks were pulverized at high strain rates (>150 s-1) associated with a supershear rupture—a rupture propagating at a velocity equal to greater than that of seismic shear waves.

Subject Categories: Seismology | Structural geology, tectonics and geodynamics


No asymmetry in geomagnetic reversals recorded by 1.1-billion-year-old Keweenawan basalts pp713 - 717

Nicholas L. Swanson-Hysell, Adam C. Maloof, Benjamin P. Weiss & David A. D. Evans

doi:10.1038/ngeo622

1.1-billion-year-old volcanic rocks in North America are thought to record asymmetric geomagnetic reversals, indicating non-axial dipolar behaviour of the magnetic field. High-resolution data from Ontario suggest that the reversals were instead symmetric, and that the apparent reversal asymmetry is an aliasing effect of the low resolution of earlier samples combined with the rapid motion of North America.

Subject Category: Geomagnetism, palaeomagnetism and core processes

See also: News and Views by Meert


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Articles

Slip maxima at fault junctions and rupturing of barriers during the 2008 Wenchuan earthquake pp718 - 724

Zheng-Kang Shen, Jianbao Sun, Peizhen Zhang, Yongge Wan, Min Wang, Roland Bürgmann, Yuehua Zeng, Weijun Gan, Hua Liao & Qingliang Wang

doi:10.1038/ngeo636

The devastating Wenchuan earthquake in 2008 struck along a fault zone that showed low rates of deformation. Analysis of GPS and InSAR data suggests that, as structural barriers failed during a single earthquake, the rupture cascaded across multiple fault segments, which may explain the high magnitude of the event.

Subject Categories: Seismology | Structural geology, tectonics and geodynamics

See also: related Backstory


The cycling and redox state of nitrogen in the Archaean ocean pp725 - 729

Linda V. Godfrey & Paul G. Falkowski

doi:10.1038/ngeo633

The initial production of oxygen in early Earth's oceans altered the redox chemistry and cycling of nitrogen. A record of nitrogen isotopes from preserved organic matter indicates nitrogen cycling in the presence of free oxygen 2.67 billion years ago, about 200 million years before the first geochemical evidence for atmospheric free oxygen.

Subject Categories: Biogeochemistry | Palaeoclimate and palaeoceanography


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Erratum

The influence of climate on the tectonic evolution of mountain belts p730

Kelin X. Whipple

doi:10.1038/ngeo638


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