Transform faults revisited- a global approach

2021 ◽  
Author(s):  
Ingo Grevemeyer ◽  
Lars Rüpke ◽  
Jason Morgan ◽  
Karthik Iyper ◽  
Colin Devey
Keyword(s):  
High Resolution ◽  
Plate Tectonics ◽  
Three Dimensional ◽  
Spreading Rate ◽  
Plate Boundaries ◽  
Fracture Zones ◽  
Transform Faults ◽  
Bathymetric Data ◽  
Tectonically Active ◽  
Spreading Rates

<p>Oceanic transform faults are seismically and tectonically active major plate boundaries. Their inactive traces are called fracture zones and may cross entire ocean basins. Plate tectonics idealizes transforms to be conservative two-dimensional strike-slip boundaries where lithosphere is neither created nor destroyed, and along which the lithosphere cools and deepens as a function of plate age. Here, we present constraints from a new compilation of high-resolution multibeam bathymetric data from 41 oceanic transforms covering all spreading rates. Statistical data show that all transform faults are considerably deeper than adjacent spreading segments and that the depth of transform valleys increases with decreasing spreading rate. The trend of increasing transform depth seems to be governed by age-offset. Further, accretion at ridge-transform intersections appears strongly asymmetric, with outside corners showing shallower relief and more extensive magmatism while inside corners have deep nodal basins and appear magmatically starved. We use a three-dimensional viscoplastic numerical model to survey the relationship between transform depth and age-offset and  use high-resolution bathymetric data to study the interaction between adjacent spreading segments and transform faults at their intersection, the ridge-transform intersection or RTI. Our global compilation of multibeam bathymetry suggest that processes acting at RTIs are independent of spreading rate, contradicting deductions from gravity field observations which seemed to imply a strong spreading rate dependence of processes shaping transform faults and fracture zones.</p>

The African continental divide: Indian versus Atlantic Ocean spreading during Gondwana dispersal

2022 ◽  
Author(s):  
Alexander L. Peace ◽  
Jordan J.J. Phethean
Keyword(s):  
Indian Ocean ◽  
Atlantic Ocean ◽  
Plate Tectonics ◽  
Spreading Rate ◽  
Seafloor Spreading ◽  
Plate Tectonic ◽  
The Indian Ocean ◽  
The Mean ◽  
Spreading Rates ◽  
Indian And Atlantic Oceans

ABSTRACT It is well established that plate-tectonic processes operate on a global scale and that spatially separate but temporally coincident events may be linked. However, identifying such links in the geological record and understanding the mechanisms involved remain speculative. This is particularly acute during major geodynamic events, such as the dispersal of supercontinents, where multiple axes of breakup may be present as well as coincidental collisional events. To explore this aspect of plate tectonics, we present a detailed analysis of the temporal variation in the mean half rate of seafloor spreading in the Indian and Atlantic Oceans, as well as plate-kinematic attributes extracted from global plate-tectonic models during the dispersal of Gondwana since ca. 200 Ma. Our analysis shows that during the ~20 m.y. prior to collision between India and Asia at ca. 55 Ma, there was an increase in the mean rate of seafloor spreading in the Indian Ocean. This manifests as India rapidly accelerating toward Asia. This event was then followed by a prompt deceleration in the mean rate of Indian Ocean seafloor spreading after India collided with Asia at ca. 55 Ma. Since inception, the mean rate of seafloor spreading in the Indian Ocean has been generally greater than that in the Atlantic Ocean, and the period of fastest mean half spreading rate in the Indian Ocean was coincident with a slowdown in mean half seafloor spreading rate in the competing Atlantic Ocean. We hypothesize that faster and hotter seafloor spreading in the Indian Ocean resulted in larger ridge-push forces, which were transmitted through the African plate, leading to a slowdown in Atlantic Ocean spreading. Following collision between India and Asia, and a slowdown of Indian Ocean spreading, Atlantic spreading rates consequently increased again. We conclude that the processes in the Indian and Atlantic Oceans have likely remained coupled throughout their existence, that their individual evolution has influenced each other, and that, more generally, spreading in one basin inevitably influences proximal regions. While we do not believe that ridge push is the main cause of plate motions, we consider it to have played a role in the coupling of the kinematic evolution of these oceans. The implication of this observation is that interaction and competition between nascent ocean basins and ridges during supercontinent dispersal exert a significant control on resultant continental configuration.

Marie Tharp: Seafloor mapping and ocean plate tectonics

2020 ◽  
Author(s):  
Mathilde Cannat ◽  
Deborah Smith ◽  
Daniel Fornari ◽  
Vicki Ferrini ◽  
Javier Escartin
Keyword(s):  
Plate Tectonics ◽  
Essential Element ◽  
Central Valley ◽  
Fracture Zones ◽  
Transform Faults ◽  
Seafloor Mapping ◽  
Mid Ocean Ridge ◽  
The 1960S ◽  
Ocean Ridge ◽  
Central Atlantic

<p><span>The pioneering seafloor mapping by Marie Tharp played a key role in the acceptance of the plate tectonic theory. Her physiographic maps,  published with Bruce Heezen,  covered the Earth’s oceans and revealed with astonishing accuracy the submarine landscape. She exposed the full extent of the global mid-ocean ridge system, documented features such as seamounts and volcanic chains, trenches, and transform faults. Marie Tharp co-authored the first papers describing the major fracture zones in the Central Atlantic (Chain, Romanche, Vema). In 1952, she also discovered that the Atlantic ridge has a central valley (the axial valley), and convinced her colleague Bruce Heezen that it, which corresponds to sustained seismicity (highlighted by other researchers at the same time thanks to the worldwide networking of seismological stations), is a rift that separates the eastern and western provinces of the Atlantic Ocean. Tharp and Heezen were not yet talking about plate tectonics at this time. But when, at the beginning of the 1960s, the first magnetic anomaly maps showed that the oceans were "young", and that the age of the seabed increased with the distance from the ridges, their physiographic map became an essential element in understanding the role that these ridges play, as well as the distribution of the main current terrestrial plates. In this poster, we present original maps and sketches that document this key contribution to the understanding of the Earth's tectonics.</span></p>

Validation of the SAMOA Operational Forecasting System in Spanish Mediterranean Ports

2020 ◽  
Author(s):  
María Liste Muñoz ◽  
Marc Mestres Ridge ◽  
Manuel Espino Infantes ◽  
Manel Grifoll Colls ◽  
Agustín Sanchez-Arcilla ◽  
...  
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Cargo Handling ◽  
Bathymetric Data ◽  
Port Authorities ◽  
Port Operations ◽  
Coastal Marine ◽  
Look Ahead ◽  
Forecasting System ◽  
Prediction Systems

<p>Working in the coastal marine environment is highly challenging, among other reasons, due to the variety of extreme, seasonal, short and long-term environmental conditions that affect the coastline, beaches, infrastructures and port operations. The maritime climate directly affects the construction and maintenance of port infrastructures, the access of ships to ports, the safety of cargo handling operations, emergency response or the environmental management of effects of port operations. Currently, the ability to predict the sea state from a few hours to days has reached levels of precision and reliability unbelievable a few years ago. And all this, in combination with numerical measurements and predictions, has enabled significant advances in knowledge about meteorological and oceanographic conditions, making possible the development of forecasting systems to provide real, accurate and safe support in decision making in ports.</p><p>SAMOA initiative (System of Meteorological and Oceanographic Support for Port Authorities), developed by Spanish Port System (Puertos del Estado), in cooperation with Spanish Port Authorities, provides high-resolution coastal operational prediction systems in domains such as harbours and nearby coastal waters.</p><p>We present a high-resolution coastal operational prediction system which simulates the hydrodynamic in the Spanish Mediterranean Ports from April to September 2019. Bathymetry was built using a combination of bathymetric data from GEBCO (General Bathymetric Chart of the Oceans), and specific local high-resolution sources provided by port authorities. Daily updated hourly winds and heat and water fluxes from the Spanish Meteorological Agency forecast services were used as a surface forcing. The Regional Ocean Modelling System, ROMS, was used to investigate the hydrodynamics.</p><p>Three-day forecast of three-dimensional currents and other oceanographic variables, such as temperature, salinity, and sea level, were produced. These results were compared with field campaigns data, displaying agreements between model outputs and in-situ observations. Finally, a look ahead to the future of the operational prediction systems is provided as a useful tool to make informed decisions around port safety and efficiency.</p><p>We would like to acknowledge financial support from ECOSISTEMA-BC Project (CTM2017-84275-R), funded by the Spanish State Research Agency.</p>

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

Three-Dimensional Immunoelectron Microscopy of Yeast Cells by a New High-Resolution Replica Method

1985 ◽  
Vol 43 ◽  
pp. 562-563
Author(s):  
Hirano T. ◽  
M. Yamaguchi ◽  
M. Hayashi ◽  
Y. Sekiguchi ◽  
A. Tanaka
Keyword(s):  
High Resolution ◽  
Plasma Polymerization ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Replica Method ◽  
Yeast Cells ◽  
Dynamic Aspect ◽  
Replica Technique ◽  
Gaseous Hydrocarbon ◽  
Transmission Electron

A plasma polymerization film replica method is a new high resolution replica technique devised by Tanaka et al. in 1978. It has been developed for investigation of the three dimensional ultrastructure in biological or nonbiological specimens with the transmission electron microscope. This method is based on direct observation of the single-stage replica film, which was obtained by directly coating on the specimen surface. A plasma polymerization film was deposited by gaseous hydrocarbon monomer in a glow discharge.The present study further developed the freeze fracture method by means of a plasma polymerization film produces a three dimensional replica of chemically untreated cells and provides a clear evidence of fine structure of the yeast plasma membrane, especially the dynamic aspect of the structure of invagination (Figure 1).

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