First principles simulations of liquid Fe-S under Earth's core conditions

First principles electronic structure calculations, based upon density functional theory within the generalized gradient approximation and ultra-soft Vanderbilt pseudopotentials, have been used to simulate a liquid alloy of iron and sulfur at Earth's core conditions. We have used a sulfur concentration of $\approx 12$wt, in line with the maximum recent estimates of the sulfur abundance in the Earth's outer core. The analysis of the structural, dynamical and electronic structure properties has been used to report on the effect of the sulfur impurities on the behavior of the liquid. Although pure sulfur is known to form chains in the liquid phase, we have not found any tendency towards polymerization in our liquid simulation. Rather, a net S-S repulsion is evident, and we propose an explanation for this effect in terms of the electronic structure. The inspection of the dynamical properties of the system suggests that the sulfur impurities have a negligible effect on the viscosity of Earth's liquid core.Comment: 24 pages (including 8 figures

Accretion, structure and hydrology of intermediate spreading-rate oceanic crust from drillhole experiments and seafloor observations

Downhole measurements recorded in the context of the Ocean Drilling Program in Hole 504B, the deepest hole drilled yet into the oceanic crust, are analyzed in terms of accretion processes of the upper oceanic crust at intermediate spreading-rate. The upper part of the crust is found to support the non steady-state models of crustal accretion developed from seafloor observations (Kappel and Ryan, 1986; Gente, 1987). The continuous and vertical nature of borehole measurements provides stratigraphic and structural data that cannot be obtained solely from seafloor studies and, in turn, these models define a framework to analyze the structural, hydrological, and mineralogical observations made in the hole over the past decade.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43190/1/11001_2005_Article_BF01204282.pd

Fan beheading and drainage diversion as evidence of a 3200-2800 BP earthquake event in the Esmeraldas-Tumaco seismic zone : A case study for the effects of great subduction earthquakes

The San Lorenzo area belongs to the Esmeraldas-Tumaco seismic zone where some of the strongest earthquakes of South America occurred during the 20th century. This paper provides evidence for a succession of geomorphic changes characterized by the disruption of the Quaternary drainage network and the reshaping of the Cayapas-Santiago estuary. The rise of the La Boca uplift bordered by the La Boca and San Lorenzo faults is responsible for the southward diversion of the Palabi, Tululbi, Bogotd and Carolina rivers toward the Santiago and Cayapas rivers. The increase of the discharge directed to the Cayapas River generated the change of the channel pattern downstream from the confluence, and the avulsion of a new estuary through the coastal plain. According to the dating of beach ridges the avulsion occurred in the period 3200-2800 BP. This period corresponds also to a faster accretion of the beach ridge margin, interpreted as a response to a small uplift of the shore. The coherency of the three morphologic evidences--diversion of drainage network, avulsion and increase of coastal accretion-suggest a unique morphotectonic event, in relation with the activity of the Esmaraldas-Tumaco seismic zone. The opening of a direct communication through the mangrove margin may have brought favorable conditions for the development of the La Tolita archaeological site after 3000 BP. (c) 2005 Elsevier B.V. All rights reserved

Experimental set-up for gas balance measurement at JET

Preprint of a lecture presented at 11. Int. Vacuum Congress, Cologne (DE), 25-29 Sep 1989SIGLEAvailable from British Library Document Supply Centre- DSC:4672.262(JET-P--89/51) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

El área septentrional andina

En este volumen se recogen la mayor parte de las ponencias que fueron presentadas en el Simposio El Área Ecuatorial Andina: Regionalización, periodización e intercambio, que tuvo lugar dentro del 49 Congreso Internacional de Americanistas, (Julio de 1997 en la ciudad de Quito). La biodiversidad del Área Ecuatorial Andina generó formas precoces de organización social, diferentes adaptaciones medio ambientales y varias redes de intercambio entre distintas regiones y con otras sociedades de Andinoamérica y Mesoamérica. En consecuencia, las ponencias que siguen, presentan una gran variedad temática, que puede afectar, en cierta medida a la coherencia del presente volumen, pero que ofrece a cambio la ventaja de mostrar una visión de conjunto de las actuaciones que se están Ilevando a cabo con toda su complejidad, poniendo las zonas en blanco y los temas olvidados, e invitando a la reflexión a cerca de las necesidades a cubrir en futuras investigaciones