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Editorial

Earthquakes off Sumatra p69

doi:10.1038/ngeo773

Indonesia's tsunami-warning system is scheduled to enter full operational mode by March 2010. The sooner it runs, the better: the threat of a tsunamigenic earthquake in the region is still imminent.


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Correspondence

The September 2009 Padang earthquake pp70 - 71

John McCloskey, Dietrich Lange, Frederik Tilmann, Suleyman S. Nalbant, Andrew F. Bell, Danny Hilman Natawidjaja & Andreas Rietbrock

doi:10.1038/ngeo753


Darwin's geological time dilemma pp71 - 72

U. Kutschera

doi:10.1038/ngeo767


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Research Highlights


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News and Views

Planetary science: Tectonic overturn on Enceladus pp75 - 76

Paul Helfenstein

doi:10.1038/ngeo763

The south pole of Saturn's icy moon Enceladus is anomalously warm, geologically youthful and cryovolcanically active. Episodic convective overturn explains how the moon's modest sources of internal heat can be channelled into intense geological activity.

Subject Category: Planetary science

See also: Letter by O’Neill & Nimmo


Hydrology: All mixed up? p76

Anna Armstrong

doi:10.1038/ngeo769


Hydrology: Soil-water bypass pp77 - 78

Fred M. Phillips

doi:10.1038/ngeo762

Hydrologists have thought of soil as a kind of giant sponge that soaks up precipitation and slowly releases it to streams. But according to new evidence the soil water used by vegetation may be largely decoupled from the water that flows through soils to streams.

Subject Category: Hydrology, hydrogeology and limnology

See also: Letter by Renée Brooks et al.


Earth's interior: Intraplate upwelling p78

Amy Whitchurch

doi:10.1038/ngeo768


Tectonics: Sinking continents pp79 - 80

R. Dietmar Müller

doi:10.1038/ngeo751

The sequence of events during the collision between India and Eurasia has long been contested. Numerical simulations imply that the key to the puzzle could lie in the subduction of continental lithosphere.

Subject Category: Structural geology, tectonics and geodynamics

See also: Letter by Capitanio et al.


Palaeoclimate: Extreme iceberg generation exposed pp80 - 81

Christina Hulbe

doi:10.1038/ngeo759

In the North Atlantic region, six massive iceberg discharge events marked the last glacial period. A numerical model now links these events to ocean temperatures and ice-shelf conditions.

Subject Category: Palaeoclimate and palaeoceanography

See also: Letter by Alvarez-Solas et al.


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Progress Article

Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic pp83 - 87

W. G. Burgess, M. A. Hoque, H. A. Michael, C. I. Voss, G. N. Breit & K. M. Ahmed

doi:10.1038/ngeo750

Arsenic levels in shallow groundwater in the Bengal Basin exceed thresholds for safe drinking water. Groundwater modelling indicates that deep wells that reach safe water below 150 m could remain safe for centuries if used for domestic water only, whereas the intensive use of deep groundwater for irrigation could contaminate this resource within decades.

Subject Categories: Biogeochemistry | Hydrology, hydrogeology and limnology


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Letters

The role of episodic overturn in generating the surface geology and heat flow on Enceladus pp88 - 91

Craig O’Neill & Francis Nimmo

doi:10.1038/ngeo731

Saturn’s satellite Enceladus shows higher heat loss than expected and a wide range of surface ages. Numerical simulations indicate that occasional catastrophic overturn events could be responsible for both observations by recycling portions of the icy lid to the interior, which would cause transiently enhanced heat loss.

Subject Category: Planetary science

See also: News and Views by Helfenstein


Contribution of Alaskan glaciers to sea-level rise derived from satellite imagery pp92 - 95

E. Berthier, E. Schiefer, G. K. C. Clarke, B. Menounos & F. Rémy

doi:10.1038/ngeo737

Over the past 50 years, retreating glaciers and ice caps have contributed 0.5mmyr−1 to sea-level rise, and one third of this contribution is believed to come from ice masses bordering the Gulf of Alaska. A combination of a comprehensive glacier inventory with high-resolution elevation data indicates that the ice loss from Alaskan glaciers is 34% less than previously thought.

Subject Categories: Climate science | Cryospheric science


Long-term persistence of oil from the Exxon Valdez spill in two-layer beaches pp96 - 99

Hailong Li & Michel C. Boufadel

doi:10.1038/ngeo749

Oil spilt from the tanker Exxon Valdez more than 20years ago still persists in the gravel beaches of Prince William Sound, Alaska. Field data and numerical modelling indicate that some of the oil was trapped in the anoxic environment of the lower layers of the beaches when the water table was low.

Subject Category: Biogeochemistry

See also: related Backstory


Ecohydrologic separation of water between trees and streams in a Mediterranean climate pp100 - 104

J. Renée Brooks, Holly R. Barnard, Rob Coulombe & Jeffrey J. McDonnell

doi:10.1038/ngeo722

Water movement in upland humid watersheds from the soil surface to the stream is often described using the concept of translatory flow, which assumes that water at any soil depth is well mixed. A study of water isotopes in an Oregon watershed instead suggests that trees and streams tap into separate water reservoirs.

Subject Category: Hydrology, hydrogeology and limnology

See also: News and Views by Phillips


Significant effect of sediment cohesion on delta morphology pp105 - 109

Douglas A. Edmonds & Rudy L. Slingerland

doi:10.1038/ngeo730

Delta morphology is thought to be controlled by factors such as river discharge, tides and waves. Numerical modelling shows that sediment cohesion also strongly influences the development of a delta’s characteristics.

Subject Category: Geomorphology


Moisture variability in the southwestern United States linked to abrupt glacial climate change pp110 - 113

J. D. M. Wagner, J. E. Cole, J. W. Beck, P. J. Patchett, G. M. Henderson & H. R. Barnett

doi:10.1038/ngeo707

The atmospheric response to millennial-scale circulation changes in the North Atlantic Ocean during the last glacial period has been difficult to constrain. Cave deposits from southwestern North America reveal that atmospheric moisture in this region increased in response to slowdowns of the Atlantic meridional overturning circulation.

Subject Category: Palaeoclimate and palaeoceanography


Variable winter moisture in the southwestern United States linked to rapid glacial climate shifts pp114 - 117

Yemane Asmerom, Victor J. Polyak & Stephen J. Burns

doi:10.1038/ngeo754

The last glacial period was characterized by large, rapid climate fluctuations. An analysis of a speleothem from New Mexico shows that the coldest conditions over Greenland coincide with increased winter precipitation in the southwestern United States, which can be attributed to a southward displacement of the polar jet stream and the North American storm track.

Subject Category: Palaeoclimate and palaeoceanography


Influence of Bering Strait flow and North Atlantic circulation on glacial sea-level changes pp118 - 121

Aixue Hu, Gerald A. Meehl, Bette L. Otto-Bliesner, Claire Waelbroeck, Weiqing Han, Marie-France Loutre, Kurt Lambeck, Jerry X. Mitrovica & Nan Rosenbloom

doi:10.1038/ngeo729

Throughout the most recent glacial period sea level fluctuated by 20–30m. Climate model simulations indicate that the barrier to water exchange between the Atlantic and Pacific oceans posed by the Bering Strait during low sea levels could have been instrumental in generating these fluctuations.

Subject Category: Palaeoclimate and palaeoceanography


Links between ocean temperature and iceberg discharge during Heinrich events pp122 - 126

Jorge Alvarez-Solas, Sylvie Charbit, Catherine Ritz, Didier Paillard, Gilles Ramstein & Christophe Dumas

doi:10.1038/ngeo752

The last glacial period was punctuated by several periods of massive iceberg discharge from the Northern Hemisphere ice sheets. Numerical simulations indicate that these discharge events are linked to an interplay between ice-sheet accumulation, marine ice-shelf stability and periodically oscillating surface ocean temperature.

Subject Category: Palaeoclimate and palaeoceanography

See also: News and Views by Hulbe


The nature of millennial-scale climate variability during the past two glacial periods pp127 - 131

V. Margari, L. C. Skinner, P. C. Tzedakis, A. Ganopolski, M. Vautravers & N. J. Shackleton

doi:10.1038/ngeo740

Periodic iceberg discharges during the last glacial period led to a slowdown of the Atlantic meridional overturning circulation. Sediment records from the Portuguese margin show that similar events punctuated the penultimate glacial period as well, although their duration and broader climatic impacts were modified by different background climate conditions.

Subject Category: Palaeoclimate and palaeoceanography


Slip-rate variability and distributed deformation in the Marmara Sea fault system pp132 - 135

Tobias Hergert & Oliver Heidbach

doi:10.1038/ngeo739

The slip rate along a fault controls the accumulation of strain that is eventually released during an earthquake. Estimates from a three-dimensional geomechanical model of the slip rate on the main Marmara fault near Istanbul, Turkey reconcile geodetic and geological observations and indicate smaller values and higher variability than previously thought.

Subject Category: Structural geology, tectonics and geodynamics


India–Asia convergence driven by the subduction of the Greater Indian continent pp136 - 139

F. A. Capitanio, G. Morra, S. Goes, R. F. Weinberg & L. Moresi

doi:10.1038/ngeo725

The most spectacular example of plate convergence on Earth was the motion of the Indian plate towards Eurasia, and the subsequent collision. Density estimates of the Greater Indian continent, after its upper crust is scraped off at the Himalayan front, suggest that this continental plate is readily subductable, potentially explaining why the convergence did not halt on collision.

Subject Category: Structural geology, tectonics and geodynamics

See also: News and Views by Müller


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Corrigendum

Multiple origins of linear dunes on Earth and Titan p139

Rubin David M. & Hesp Patrick A.

doi:10.1038/ngeo774


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Backstory

Spoilt beauty p140

doi:10.1038/ngeo766


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