Emplacement mechanisms of the South Kona slide complex,Hawaii Island: sampling and observations by remotely operated vehicle Kaiko

Emplacement of a giant submarine slide complex, offshore of South Kona, Hawaii Island, was investigated in 2001 by visual observation and in-situ sampling on the bench scarp and a megablock, during two dives utilizing the Remotely Operated Vehicle (ROV) Kaiko and its mother ship R/V Kairei. Topography of the bench scarp and megablocks were defined in 3-D perspective, using high-resolution digital bathymetric data acquired during the cruise. Compositions of 34 rock samples provide constraints on the landslide source regions and emplacement mechanisms. The bench scarp consists mainly of highly fractured, vesiculated, and oxidized aa lavas that slumped from the subaerial flank of ancestral Mauna Loa. The megablock contains three units: block facies, matrix facies, and draped sediment. The block facies contains hyaloclastite interbedded with massive lava, which slid from the shallow submarine flank of ancestral Mauna Loa, as indicated by glassy groundmass of the hyaloclastite, low oxidation state, and low sulfur content. The matrix facies, which directly overlies the block facies and is similar to a lahar deposit, is thought to have been deposited from the water column immediately after the South Kona slide event. The draped sediment is a thin high-density turbidite layer that may be a distal facies of the Alika-2 debris-avalanche deposit; its composition overlaps with rocks from subaerial Mauna Loa. The deposits generated by the South Kona slide vary from debris avalanche deposit to turbidite. Spatial distribution of the deposits is consistent with deposits related to large landslides adjacent to other Hawaiian volcanoes and the Canary Islands.     

Landscape for change? International climate policy and energy transitions: evidence from sub-Saharan Africa

What is the role of the climate regime in facilitating rapid decarbonization of the world’s energy systems? We examine how core assumptions concerning the roles of the nation state, carbon markets and finance and technology in international climate policy are being challenged by the realities of how transitions in the energy systems are unfolding. Drawing on the critical region of sub-Saharan Africa, we examine the potential for international climate policy to foster new trajectories towards decarbonization.

Policy relevance

The international regime for climate policy has been in place for some twenty years. Despite significant changes in the landscape of energy systems and drivers of global GHG emissions over this time, the core principles and tools remain relatively stable – national governments, carbon markets, project-based climate finance and the transfer of technological hardware. Given the diversity of actors and drivers and the limited direct reach and influence of international climate policy, however, there is an urgent need to consider how the climate regime can best support the embryonic transitions that are slowly taking form around the world. To do this effectively requires a more nuanced understanding of the role of the state in governing these transitions beyond the notion of a cohesive state serving as rule-enforcer and transition manager. It also requires a broader view of technology, not just as hardware that is transferred, but as a set of practices and networks of expertise and enabling actors. Likewise, though markets have an important role to play as vehicles for achieving broader ends, they are not an end in themselves. Finally on finance, while acknowledging the important role of climate aid, often as a multiplier or facilitator of more ambitious private flows, it is critical to differentiate between the types of finance required for different transitions, many of which will not be counted under, or directed by, the climate regime. In sum, the (low-) carbon economy is being built in ways and in numerous sites that the climate regime needs to be cognizant of and engage with productively, and this may require fundamental reconsideration of the building blocks of the international climate regime.     

Refinement of the late Quaternary geologic history of Erebus volcano,Antarctica using Ar/Ar and Cl age determinations

Six new ⁴⁰Ar/³⁹Ar and three cosmogenic ³⁶Cl age determinations provide new insight into the late Quaternary eruptive history of Erebus volcano. Anorthoclase from 3 lava flows on the caldera rim have ⁴⁰Ar/³⁹Ar ages of 23 ± 12, 81 ± 3 and 172 ± 10 ka (all uncertainties 2σ). The ages confirm the presence of a second, younger, superimposed caldera near the southwestern margin of the summit plateau and show that eruptive activity has occurred in the summit region for 77 ± 13 ka longer than previously thought. Trachyte from “Ice Station” on the eastern flank is 159 ± 2 ka, similar in age to those at Bomb Peak and Aurora Cliffs. The widespread occurrences of trachyte on the eastern flank of Erebus suggest a major previously unrecognized episode of trachytic volcanism. The trachyte lavas are chemically and isotopically distinct from alkaline lavas erupted contemporaneously in the summit region < 5 km away.     

Soil water residence times and solute uptake on a dolomite bedrock—preliminary results

Calcium and magnesium levels have been monitored in slope foot drainage waters on a dolomite bedrock. Both calcium and magnesium rich pulses occur. Short term dissolution experiments demonstrate high calcium levels in solution while other authors have suggested that long residence time groundwater has relatively high levels of magnesium due to calcite precipitation. Patterns of field fluctuations in Ca: Mg ratios can thus be tentatively interpreted in terms of short residence time water of high calcium content mixing with long residence time water of high magnesium content. Fluorometric dye tracing has been used to indicate the orders of magnitude of soil water residence times, suggesting that quickflow components are resident in the system for a few hours to a few days. Further work is in progress.     

Linear volcanoes along the Pacific-Cocos plate boundary, 9°N to the Galapagos triple junction

A Seabeam-based reconnaissance of the 500 km of the East Pacific Rise crest between 7°N and 2°40′N shows that the axial ridge is segmented by four 4–13 km non-transform offsets into an en echelon string of distinctively different linear volcanoes. These axial volcanoes are oriented orthogonal to relative plate motion, except where their overlapping ends veer 15° toward each other and where small intra-volcano offsets of their crestal rift zones create abrupt kinks. Longitudinal gradients of the crestlines are less than 5 m/km, except where they plunge at rift-zones' overlapped ends and where they rise locally to small axial peaks. Transverse profiles vary from trapezoidal to triangular, with a steep shield-shaped cross-section being most common. Conventional sounding data indicate that this pattern continues to the 140 km-offset Siqueiros transform fault system at 8.2°N. Within this fault system is a short spreadingcenter volcano contained in a rift valley that links two strike-slip fault zones. Immediately to the north is the shallow 9.0°–8.3°N axial volcano, with unusual relief mapped by a deeply towed instrument package. At the southern end of the plate boundary, as the rise crest enters the region of the Pacific-Cocos-Nazca triple junction, the axial ridge narrows, deepens, and acquires a more irregular long profile. South of 2°30′N the rise crest has a 15 km-wide rift valley that contains multiple volcanic ridges with north-south strikes. Structural hypotheses suggested or supported by these morphologic observations include a point-source magma supply to the spreading center from mantle diapirs, the along-strike continuity of axial magma chambers on fast-spreading rises, even across small rift-zone offsets, and the importance of magma intrusion as well as eruption for building the axial ridge. Hypotheses inconsistent with the new data include magma supply and long-distance dispersal from a few widely spaced plumes, primary control of the topographic, volcanic, and tectonic characteristics of the rise crest by distance from transform faults, and localization of triple junctions over major mantle upwellings.     

Neue Ergebnisse zur Tektonik der Allgäuer und Vilser Alpen

Zusammenfassung Eine Neuuntersuchung der Tektonik in den Vilser Alpen und im Hochvogelgebiet, wo die Frage seit langer Zeit diskutiert wird, ob dort die Allgäu- und Lechtal-Decke getrennte Einheiten bilden, oder stratigraphisch untrennbar zusammenhängen, erbrachte eine eindeutige Entscheidung für den Deckenbau. Der Verlauf der Deckengrenze konnte zwischen Hochvogel und Hohenschwangauer Alpen präzisiert werden. Der interne Falten- und Schuppenbau der Lechtal-Decke hat nirgends zur Bildung von tektonisch tieferen Teildekken geführt, die internen Verschuppungen besitzen nur ein geringes Ausmaß.

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A new investigation of the tectonics in the Vilser Alps and in the Mt. Hochvogel area where since a long time a discussion was going on if the thrust sheets of Allgäu and Lechtal-Decke are separate units or connected by stratigraphic sequences, a definite decision could be made in favour of the nappe structure in this part of the Northern Calcareous Alps. The internal structure of the Lechtal-Decke thrust sheet is characterized by local imbricate structure which originate from sheared folds.

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Résumé On a dicuté depuis longtemps dans les Vilser Alpen et dans la région du Mont Hochvogel le problème, si les nappes de Allgäu et Lechtal-Decke sont des unités separées ou qu'ils forment une partie inséparable par des séquences stratigraphiques. Une nouvelle examen de la tectonique a affirmé la structure de nappes dans cette région des Alpes Calcaires du Nord. La structure intérieure de la nappe de Lechtal-Decke est caracterisée par une structure écaillée locale, qui se developpe de plis cisaillés.

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Amplification of primordial magnetic fields by anisotropic gravitational collapse

If a magnetic field is frozen into a plasma that undergoes spherical compression, then the magnetic field B varies with the plasma density ρ according to   B ∝ρ^2/3  . In the gravitational collapse of cosmological density perturbations, however, quasi-spherical evolution is very unlikely. In anisotropic collapses the magnetic field can be a much steeper function of gas density than in the isotropic case. We investigate the distribution of amplifications in realistic gravitational collapses from Gaussian initial fluctuations using the Zel'dovich approximation. Representing our results using a relation of the form   B ∝ρ^α  , we show that the median value of α can be much larger than the value  α= 2/3  resulting from spherical collapse, even if there is no initial correlation between magnetic field and principal collapse directions. These analytic arguments go some way towards understanding the results of numerical simulations.