Eric Mittelstaedt

Magmatic and tectonic evolution of the North Atlantic

The primary aim of the present paper is (1) to review the tectonomagmatic evolution of the North Atlantic, and (2) constrain evolutionary models with new lithosphere strength estimates and interpretation of potential field data north of Iceland. Our interpretations suggest that the breakup along the entire eastern Jan Mayen Ridge occurred at c. 55 Ma. Calculations of lithospheric yield strength indicate that the continental rifting in East Greenland, which led to oceanic crustal formation west of the Jan Mayen Ridge at c. 25 Ma, could have started at c. 42.5 Ma. Symmetrical V-shaped gravimetric ridges, which can be traced back to c. 48 Ma, document large-scale asthenospheric flow both north and south of Iceland. Such flow is predicted by geodynamic models of mantle plumes, but has yet to be predicted by other mechanisms. The results from the compartments north of Iceland, viewed in a regional context, strengthen the hypothesis attributing the anomalous magmatism in the North Atlantic area from c. 70 Ma to the present to the Icelandic plume.

Diffuse venting at the ASHES hydrothermal field : heat flux and tidally modulated flow variability derived from in situ time-series measurements

Time-series measurements of diffuse exit-fluid temperature and velocity collected with a new, deep-sea camera, and temperature measurement system, the Diffuse Effluent Measurement System (DEMS), were examined from a fracture network within the ASHES hydrothermal field located in the caldera of Axial Seamount, Juan de Fuca Ridge. The DEMS was installed using the HOV Alvin above a fracture near the Phoenix vent. The system collected 20 s of 20 Hz video imagery and 24 s of 1 Hz temperature measurements each hour between 22 July and 2 August 2014. Fluid velocities were calculated using the Diffuse Fluid Velocimetry (DFV) technique. Over the 12 day deployment, median upwelling rates and mean fluid temperature anomalies ranged from 0.5 to 6 cm/s and 08C to 6.58C above ambient, yielding a heat flux of 0.29 6 0.22 MW m and heat output of 3.16 2.5 kW. Using a photo mosaic to measure fracture dimensions, the total diffuse heat output from cracks across ASHES field is estimated to be 2.05 6 1.95 MW. Variability in temperatures and velocities are strongest at semidiurnal periods and show significant coherence with tidal height variations. These data indicate that periodic variability near Phoenix vent is modulated both by tidally controlled bottom currents and seafloor pressure, with seafloor pressures being the dominant influence. These results emphasize the importance of local permeability on diffuse hydrothermal venting at mid-ocean ridges and the need to better quantify heat flux associated with young oceanic crust.

The Galápagos: A Natural Laboratory for the Earth Sciences

The Galápagos Islands are renown for their unique flora and fauna, inspiring Charles Darwin in the elaboration of his theory of evolution. Yet in his Voyage of the Beagle, published in 1839, Darwin also remarked on the fascinating geology and volcanic origin of these enchanted Islands. Since then, the Galápagos continue to provide scientists with inspiration and invaluable information about ocean island formation and evolution, mantle plumes, and the deep Earth.

Moving lithospheric modeling forward: Attributes of a community computer code

GS A TO DA Y | JU NE 20 15 C.M. Cooper, Washington State University, School of the Environment, P.O. Box 624812, Pullman, Washington 99164-2812, USA; Eric Mittelstaedt, University of Idaho, Dept. of Geological Sciences, 875 Perimeter Drive, MS 3022, Moscow, Idaho 838443022, USA; Claire Currie, University of Alberta, Dept. of Physics, Edmonton, Alberta, Canada T6G 2G7; Jolante van Wijk, New Mexico Institute of Mining and Technology, Dept. of Earth & Environmental Science, 801 Leroy Place, Socorro, New Mexico 87801, USA; Louise Kellogg, Lorraine Hwang, University of California Davis, Earth and Planetary Sciences, Computational Infrastructure for Geodynamics, 2215 Earth and Physical Sciences, One Shields Avenue, Davis, California 95616, USA; and Ramon Arrowsmith, Arizona State University, School of Earth & Space Exploration, P.O. Box 876004, Tempe, Arizona 85287-6004, USA

Optical methods to monitor temporal changes at the seafloor: The Lucky Strike deep-sea hydrothermal vent field (Mid-Atlantic Ridge)

Newly developed image processing techniques, including gigamosaicing, video-based 3D terrain reconstruction, and video-based fluid velocimetry have provided key information to understand the distribution, nature, and quantification of hydrothermal activity at a deep sea vent field (Lucky Strike, Mid-Atlantic Ridge). These imaging techniques have been coupled with seafloor instrumentation and sampling, allowing us to develop a comprehensive approach to study active processes in the submarine environment that can be transferred to other study areas.

Accretion mode of oceanic ridges governed by axial mechanical strength

Oceanic spreading ridges exhibit structural changes as a function of spreading rate, mantle temperature and the balance of tectonic and magmatic accretion. The role that these or other processes have in governing the overall shape of oceanic ridges is unclear. Here, we use laboratory experiments to simulate ridge spreading in colloidal aqueous dispersions whose rheology evolves from purely viscous to elastic and brittle when placed in contact with a saline water solution. We find that ridge shape becomes increasingly linear with spreading rate until reaching a minimum tortuosity. This behaviour is predicted by the axial failure parameter ΠF, a dimensionless number describing the balance of brittle and plastic failure of axial lithosphere. Slow-spreading, fault-dominated and fast-spreading, fluid intrusion-dominated ridges on Earth and in the laboratory are separated by the same critical ΠF value, suggesting that the axial failure mode governs ridge geometry. Values of ΠF can also be calculated for different mantle temperatures and applied to other planets or the early Earth. For higher mantle temperatures during the Archaean, our results preclude the predicted formation of large tectonic plates at high spreading velocity.The shape of mid-ocean ridges is influenced by lithospheric mechanical strength, according to laboratory simulations of diverging plates. The results imply that large tectonic plates probably could not have formed on a younger, hotter Earth.

Crustal magnetization and the subseafloor structure of the ASHES vent field, Axial Seamount, Juan de Fuca Ridge: Implications for the investigation of hydrothermal sites

High-resolution geophysical data have been collected using the Autonomous Underwater Vehicle (AUV) Sentry over the ASHES (Axial Seamount Hydrothermal Emission Study) high-temperature (~348°C) vent field at Axial Seamount, on the Juan de Fuca Ridge. Multiple surveys were performed on a 3-D grid at different altitudes above the seafloor, providing an unprecedented view of magnetic data resolution as a function of altitude above the seafloor. Magnetic data derived near the seafloor show that the ASHES field is characterized by a zone of low magnetization, which can be explained by hydrothermal alteration of the host volcanic rocks. Surface manifestations of hydrothermal activity at the ASHES vent field are likely controlled by a combination of local faults and fractures and different lava morphologies near the seafloor. Three-dimensional inversion of the magnetic data provides evidence of a vertical, pipe-like upflow zone of the hydrothermal fluids with a vertical extent of ~100m.

The Final Stages of Slip and Volcanism on an Oceanic Detachment Fault at 13°48′N, Mid‐Atlantic Ridge

Author(s): Parnell-Turner, RE; Mittelstaedt, E; Kurz, MD; Jones, MR; Soule, SA; Klein, F; Wanless, VD; Fornari, DJ

Drying colloidal systems: Laboratory models for a wide range of applications

Abstract.The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art.Graphical abstract