Wadati benioff zone zone of seismicity created by slip between upper surface of slab and lithosphere of the uppe

      Wadati-Benioff zone: zone of seismicity created by slip between upper surface of slab and lithosphere of the upper plate Reminder / change in schedule  Friday is a discussion of the paper “How Erosion Builds Mountains” by Pinter and Brandon. Paper is on electronic reserve  On Wednesday, we will talk about tectonic basins Rift to drift: a story of extension Four main stages related to Wilson cycle  RIFT VALLEY  ! "Example: East African Rift  YOUTHFUL#$ !%&! !'Example: Red Sea  MATURE# Example: most of the present Atlantic continental margins  FRACTURE# Fates of continental rift elements  ()!  )  ! !  ! )    Currently active continental rifts  *+!!,  -.!  /0-  12!   (! Some former continental rifts  -.*  *1  3  !4  3  !4  1 1  !) Elements of extensional system  54 4 !  04   (      /    Thermal and uplift history  +)#!   5'   !  !  ! ISOSTASY ISOSTASY Isostasy: the state of gravitational equilibrium between the Earth's lithosphere (analogous to iceberg) and asthenosphere (analogous to seawater). Tectonic plates ‘float’ at an elevation which depends on their thickness and relative density; thus high areas will have large lithospheric ‘roots’. Where a balance is achieved between topography and size of roots, lithosphere is said to be in  6. [...]... characterized by rhyolite and basalt Contrasts with andesitic volcanism of arcs QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture Rift basin sedimentation      sediment depocenters: accommodation space may be 10s of km deep immature sediments (lots of feldspar, lithic fragments) half grabens common Fault-controlled patterns of sedimentation: alluvial fans and debris... changes = segmentation of depocenters Depocenter symmetry will reflect structural symmetry  Pure Shear  Simple Shear Conceptual models of rift evolution  passive vs active rifting Passive - in response to far-field stress  Active - in response to upwelling of asthenospheric mantle  rift tip propagation: Gulf of California  influence of previous structure: Tertiary formation of the Atlantic Ocean... upwelling of asthenospheric mantle  rift tip propagation: Gulf of California  influence of previous structure: Tertiary formation of the Atlantic Ocean  hot spots, triple junctions and aulocogens  Rift to drift: a story of extension http://www.mines.utah.edu/geo/courses/UOnline/slideshow/contrift_1.html Establishing a passive margin .       Wadati-Benioff zone: zone of seismicity created by slip between upper surface of slab and lithosphere of the upper plate Reminder / change in schedule  Friday is a discussion of the.   !  !  ! ISOSTASY ISOSTASY Isostasy: the state of gravitational equilibrium between the Earth's lithosphere (analogous to iceberg) and asthenosphere (analogous to seawater). Tectonic. which depends on their thickness and relative density; thus high areas will have large lithospheric ‘roots’. Where a balance is achieved between topography and size of roots, lithosphere is