Studies of the structure of mid-ocean ridges and the processes involved at these accreting plate boundaries have played an important role in the development of plate tectonics models over the last two decades. During this time our concept of the accretion/spreading process has evolved from a two-dimensional, steady-state picture to a three dimensional, time-dependent view of the volcanism and r...

Numerical models show that maximum dike width at oceanic spreading centers should scale with axial lithospheric thickness if the pre-diking horizontal stress is close to the Andersonian normal faulting stress and the stress is fully released in one dike intrusion. Dikes at slow-spreading ridges could be over 5 m wide and maximum dike width should decrease with increasing plate spreading rate. H...

In a previous paper (“Part 1”) it was shown that a combination of temperature-dependent viscosity and visco-plastic yielding is sufficient to give rudimentary plate tectonic-like behavior in three-dimensional models of mantle convection. Here, the calculations are extended to include two complexities which have been suggested as important in localizing deformation at plate boundaries: strain we...

Volcanic hotspots and mid-ocean ridge spreading centers are the surface expressions of upwelling in Earth's mantle convection system, and their interaction provides unique information on upwelling dynamics. I investigated the influence of the Iceland hotspot on the adjacent mid-Atlantic spreading center using phase-delay times of seismic surface waves, which show anomalous polarization anisotro...

Introduction Hydrothermal systems and their associated metal deposits have been studied at oceanic spreading centers since the late 1970s when they were first discovered. More recently, those studies have been extended to subduction zone hydrothermal systems including active volcanic arcs and back-arc environments. Oceanic spreading centers compose a global ridge system where new ocean crust is...

the space structure that governs cities has depended on several corresponding relations and various factors which consist of: population, job and activities, transportation patterns, urban sub-structures, various services and etc that always were connected to each other and have formed its space structure. but since these relations are more complicated in big cities, the importance of paying at...