A triple junction is a place where three lithospheric plates meet. Lithospheric plates are typically considered to be rigid except along narrow, discrete boundary zones with adjacent plates. A significant number of triple junctions in the current plate system involve distributed plate boundaries: broad zones across which the motion of one lithospheric plate relative to an adjacent plate is accommodated by deformation. Instantaneous velocities of plate-boundary points can be derived from global plate-motion models or from GPS/GNSS data. Such instantaneous velocities can help characterize whether an individual boundary at a triple junction is divergent, convergent, transform, or oblique (i.e., combining transform and divergent/convergent motion). There are 25 unique types of triple junction, defined by the types of boundaries that meet at the triple junction. In the 56-plate system that is frequently used to describe current tectonics, there are 108 triple junctions. First-generation models of triple junctions assumed that a point on one plate moves in a circular trajectory relative to an adjacent plate over finite time intervals, but we now know that this assumption is not generally valid. Triple junction geometry is now thought to evolve dynamically over time for most, if not all, triple junctions.
原文链接
分享
引用
