Solid Earth sciences articles within Nature

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  • Letter |

    Radiative forcing over an '11-year' solar cycle is thought to be in phase with related influences on climate, but recent satellite data reveal a surprising spectral component in solar variability. These authors show that these spectral variations lead to decreases in ozone below 45 km and increases above. As a consequence, radiative forcing of surface climate is out of phase with solar activity, suggesting that a major revision of our current understanding of solar forcing of climate may be required.

    • Joanna D. Haigh
    • , Ann R. Winning
    •  & Jerald W. Harder

  • Letter |

    These authors test whether patterns of seismicity and the stabilities of potentially relevant hydrous phases are consistent with a wet lithosphere. They show that there is nearly a one-to-one correlation between the dehydration of minerals and seismicity at depths less than ∼250 km, but no correlation at greater depths. They conclude that subducting slabs must be essentially dry by 400-km depth and thus do not provide a pathway for significant amounts of water to enter the mantle transition zone or the lower mantle.

    • Harry W. Green II
    • , Wang-Ping Chen
    •  & Michael R. Brudzinski

  • Letter |

    Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. It has recently been argued that the decay of aftershocks with distance from the main earthquake could be explained only by dynamic triggering. This hypothesis has now been tested, the conclusion being that the observed decay can be better explained by static triggering.

    • Keith Richards-Dinger
    • , Ross S. Stein
    •  & Shinji Toda

  • Letter |

    Water within glaciers and ice sheets has a strong potential to influence ice velocity and, ultimately, the rate of sea-level rise. But so far direct measurement of the magnitude and characteristics of water stored within glaciers has proved difficult. Here, a combination of in situ borehole measurements and radar and seismic imaging has been used to show that there is an extensive network of basal crevasses in the Bench Glacier in Alaska. The crevasses hold water equivalent to at least a decimetre layer.

    • Joel T. Harper
    • , John H. Bradford
    •  & Toby W. Meierbachtol

  • Letter |

    Earthquake instability has long been attributed to fault weakening during accelerated slip, but what are the mechanisms that control this weakening? Here laboratory evidence is presented for the dynamic weakening of faults that are sheared at velocities approaching earthquake slip rates. The experimental faults, made from solid granite blocks, quickly wore to form a fine-grain rock powder, known as gouge, which reduced the faults' strength. It is concluded that only newly formed gouge can weaken the experimental faults.

    • Ze’ev Reches
    •  & David A. Lockner

  • Letter |

    What defines the boundary between the Earth's lithosphere and asthenosphere? Here it is shown experimentally that the instability of the hydrous mineral pargasite at depths greater than about 90 km causes a sharp drop in the water-storage capacity of a fertile upper-mantle mineralogy, and accordingly a sharp drop in its solidus temperate. This effect might define the lithosphere–asthenosphere boundary.

    • David H. Green
    • , William O. Hibberson
    •  & Anja Rosenthal

  • Books & Arts |

    Powerful volcanoes remind us of the fragile boundary between Earth's crust and mantle, finds Laura Spinney.

    • Laura Spinney

  • Letter |

    It has been suggested that glacial erosion has an important role in controlling mountain height. Here, spatial and temporal patterns of erosion in the glaciated Patagonian Andes have been assessed with the help of a low-temperature thermochronologic data set. The results show that, between 38° S and 49° S, accelerated erosion at the onset of widespread glaciation limits mountain height. But at higher latitudes, glaciation protects the landscape from erosion and leads to growth in mountain height and width.

    • Stuart N. Thomson
    • , Mark T. Brandon
    •  & Nathaniel J. Wilson

  • News & Views |

    Glaciers frozen to bedrock may have protected the southernmost Andes from erosion, providing an explanation for the mountains' topography and fresh constraints on possible links between climate and tectonics.

    • Jean Braun

  • Letter |

    These authors show evidence for a high coherence between the slip distribution inferred from the 2010 Maule earthquake, Chile, and the patchwork of interseismic locking distribution derived from global positioning system observations during the previous decade. Their work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future earthquakes, which thus might be anticipated by geodetic observations.

    • Marcos Moreno
    • , Matthias Rosenau
    •  & Onno Oncken

  • Letter |

    The Younger Dryas — during which Northern Hemisphere temperatures cooled drastically in just a few years — is perhaps the best-known example of abrupt climate change, but its global extent is under debate, particularly in the record of glacial behaviour in New Zealand. These authors present evidence for glacial retreat in New Zealand during the Younger Dryas, supporting the hypothesis that Northern Hemisphere climate changes caused Southern Hemisphere warming through a series of climate feedbacks.

    • Michael R. Kaplan
    • , Joerg M. Schaefer
    •  & Alice M. Doughty

  • News Feature |

    A project to drill a 10-kilometre-deep hole in China will provide the best view yet of the turbulent Cretaceous period. Jane Qiu reports.

    • Jane Qiu

  • News & Views |

    Meticulous reconstruction of the former extent of a glacier high in the mountains of New Zealand will help in interpreting global-scale climatic adjustments that occurred at the end of the last glaciation.

    • Martin P. Kirkbride

  • Letter |

    Cratons, the ancient cores of continents, extend laterally for hundreds of kilometres, and are underlain to depths of 180–250 km by mantle roots that are chemically and physically distinct from surrounding mantle. But how can these roots stay so isolated from mantle convection? Here it is shown that olivine in peridotite xenoliths from the lithosphere–athenosphere boundary region of the Kaapvaal craton mantle root is water-poor, providing sufficient viscosity contrast with the underlying asthenosphere to explain the root's stability.

    • Anne H. Peslier
    • , Alan B. Woodland
    •  & Marina Lazarov

  • Editorial |

    Earth scientists have explained why Canada and South Africa are still here.

  • Article |

    These authors show that changes in seismic anisotropy with depth across the stable part of North America reveal the presence of two lithospheric layers. The top layer, which is chemically depleted, is ∼150 km thick under the ancient core of the continent and tapers out along its younger borders. The bottom of the lithosphere is relatively flat, in agreement with the presence of a thermal conductive root that subsequently formed around the depleted chemical layer.

    • Huaiyu Yuan
    •  & Barbara Romanowicz

  • Letter |

    At the end of the last ice age, rising atmospheric CO2 levels coincided with a decline in radiocarbon activity, suggesting the release of highly radiocarbon-depleted CO2 from the deep ocean to the atmosphere. These authors present radiocarbon records of surface and intermediate-depth waters from two sediment cores and find an decrease in radiocarbon activity that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial–interglacial climatic transition.

    • Kathryn A. Rose
    • , Elisabeth L. Sikes
    •  & Howard J. Spero

  • News |

    Recent measurements of gravitational constant increase uncertainty over accepted value.

    • Eugenie Samuel Reich

  • Brief Communications Arising |

    • Nina Veselka
    • , David D. McErlain
    •  & M. Brock Fenton

  • Letter |

    On 29 September 2009, a tsunami devastated the Samoan and northern Tongan islands. Here, an unusual earthquake sequence that preceded this tsunami is analysed. A magnitude-8.1 intraplate faulting event in the outer trench-slope at the northern end of the Tongan subduction zone was followed by extensive interplate faulting, with total moment equivalent to that of a magnitude-8.0 earthquake. Overlap of the seismic signals had obscured the fact that distinct faults had ruptured with different geometries.

    • Thorne Lay
    • , Charles J. Ammon
    •  & Alexander R. Hutko

  • Letter |

    On 29 September 2009, a tsunami devastated the Samoan and northern Tongan islands. It is shown here that an unusual earthquake sequence preceded this tsunami. A magnitude-8 earthquake in the outer-rise intraplate region occurred almost simultaneously with rupture of the shallow subduction interplate interface, equivalent to a magnitude-8 earthquake. The findings provide information on strain release mechanisms at subduction zones, and a possible mechanism for the occasional large tsunamis generated at the Tonga subduction zone.

    • J. Beavan
    • , X. Wang
    •  & R. Kautoke

  • News & Views |

    A puzzling case is presented by the occurrence of two large but dissimilar earthquakes at almost the same time and place. One must have acted as the trigger, but which one and how did it do so?

    • Kenji Satake

  • Letter |

    High 3He/4He ratios in some basalts have been interpreted as evidence for ancient reservoirs preserved in the Earth’s mantle; however, such rocks have never been observed to host the primitive lead-isotopic compositions required for an early formation age. These authors show that Baffin Island and West Greenland lavas exhibit primitive lead-isotope ratios consistent with a mantle source age of 4.55–4.45 billion years, and that their source may be the most ancient accessible reservoir in the mantle.

    • Matthew G. Jackson
    • , Richard W. Carlson
    •  & Jerzy Blusztajn

  • Letter |

    The earliest direct evidence for stone tools is between 2.6 and 2.5 million years old and comes from Gona, Ethiopia. These authors report bones from Dikika, Ethiopia, dated to around 3.4 million years ago and marked with cuts indicative of the use of stone tools to remove flesh and extract bone marrow. This is the earliest known evidence of stone tool use, and might be attributed to the activities of Australopithecus afarensis.

    • Shannon P. McPherron
    • , Zeresenay Alemseged
    •  & Hamdallah A. Béarat

  • Letter |

    Cloud simulation is one of the most challenging tasks in regional to global-scale modelling. In many cases, the physical mechanisms responsible for observed cloud dynamics are unknown, making it difficult to realistically simulate their structure and behaviour. These authors show that open cellular clouds — characterized by low albedo — can be created by precipitation-driven downdrafts and that the resulting cloud structure forms an oscillating, self-organizing cloud field.

    • Graham Feingold
    • , Ilan Koren
    •  & Wm. Alan Brewer

  • News & Views |

    Geochemical evidence for the existence of the mother of all mantle-source reservoirs for volcanism has come to light. The new results have provocative implications for our understanding of Earth's interior.

    • David Graham

  • News |

    Geological storage of long-lived radioactive material is moving closer to reality in Europe, says Declan Butler.

    • Declan Butler

  • Letter |

    These authors show that simultaneous crystallization and melting at the surface of the Earth's inner core can result in a translational mode of thermal convection within the inner core, producing the observed stratified layer of reduced seismic velocity at the base of the outer core. The dynamical model they propose also introduces an asymmetry between hemispheres that may explain the enigmatic East–West asymmetry in seismic properties of the inner core.

    • Thierry Alboussière
    • , Renaud Deguen
    •  & Mickaël Melzani

  • Letter |

    A spectacular adaptive radiation among notosuchian crocodyliforms in the southern continents of Gondwana led to all manner of strange forms; in particular, their teeth, rather than being undifferentiated conical fangs, were often differentiated into biting and crushing types, as seen in mammals. These authors describe a new form from the Cretaceous period of Tanzania in which upper and lower dentitions were capable of occlusion, a feature otherwise known only from mammals.

    • Patrick M. O’Connor
    • , Joseph J. W. Sertich
    •  & Jesuit Temba

  • News & Views |

    An ingenious proposal holds that Earth's inner core is solidifying in the western hemisphere and melting in the east. The process is consequent on, and reinforces, its easterly slippage — or translation.

    • Michael I. Bergman

  • Letter |

    These authors argue that the concentration of magnitude-7 or larger earthquakes in the New Madrid seismic zone since the end of the last ice age results from the recent, climate-controlled, erosional history of the northern Mississippi embayment. They show that the upward flexure of the lithosphere caused a reduction of normal stresses in the upper crust sufficient to unclamp pre-existing faults close to failure equilibrium.

    • E. Calais
    • , A. M. Freed
    •  & S. Stein

  • News & Views |

    The heartland of the United States lies within a tectonic plate, certain regions of which have experienced large and geologically recent earthquakes. Explanations for those events are still being sought.

    • Mark D. Zoback

  • Letter |

    These authors report the concentrations of hydrogen, chlorine and sulphur in the mineral apatite from a lunar basalt, and show that the concentrations are indistinguishable from apatites in common terrestrial igneous rocks. They conclude that both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable materials within the Earth.

    • Jeremy W. Boyce
    • , Yang Liu
    •  & Lawrence A. Taylor

  • Letter |

    The annual burial of organic carbon in lakes and reservoirs exceeds that of ocean sediments, but inland waters are components of the global carbon cycle that receive only limited attention. Here the authors find that the mineralization of organic carbon in lake sediments exhibits a strong positive relationship with temperature, suggesting that warmer water temperatures lead to more mineralization and less organic carbon burial.

    • Cristian Gudasz
    • , David Bastviken
    •  & Lars J. Tranvik

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