Evolución de la corteza en limite de placas convergentes.

The thermal–mechanical evolution of crustal orogenic belts at convergent plate boundaries: A reappraisal of the orogenic cycle

Olivier Vanderhaeghe

Como evoluciona la corteza en zonas de convergencia, dependiendo de la interacción entre las diferentes fuerzas y condiciones existentes.

Dynamics of crustal wedges, orogenic plateaus, metamorphic core complexes and rifts.

Thermal–mechanical evolution of the crust at plate boundaries and the crustal tectonic cycle. The thermal–mechanical evolution of the crust at plate boundaries and the crustal tectonic cycle are illustrated by the evolution of crustal thickness and Moho temperature as a function of time. The first stage of the thermal–mechanical evolution of the crust at convergent plate boundaries is characterized by the development of a crustal wedge under a low-geothermal gradient dominated by subduction. A steady-state is reached if mass redistribution by erosion counterbalances crustal accretion. If, not thermal maturation of the crustal wedge is responsible for the weakening of the lower crust which leads to the wedge/plateau transition. At this stage, the basal traction force decomposes into Ftw beneath the plateau and Fts along its edges. A steady-state is reached if accretion is balanced by gravity-driven lateral flow of the weakened crust. A modification of the lithospheric-scale dynamics boundary condition causes the switch from crustal thickening to thinning and the mode of crustal extension ranges from metamorphic core complex to rift as a function of the rheologic state of the crust. Crustal thinning is associated with isothermal decompression and is followed by thermal subsidence.

Modelo de subducción

Influence of lateral slab edge distance on plate velocity, trench velocity, and subduction partitioning

http://www.agu.org/journals/jb/jb1110/2011JB008535/

Abstract: Subduction of oceanic lithosphere occurs through both trenchward subducting plate motion and trench retreat. We investigate how subducting plate velocity, trench velocity and the partitioning of these two velocity components vary for individual subduction zone segments as a function of proximity to the closest lateral slab edge (D_SE). We present a global compilation for 207 trench segments from 17 active subduction zones on Earth and three-dimensional numerical models of progressive free subduction of a single oceanic plate that subducts into a stratified mantle. The results show that the subducting plate velocity is always high (≥5.1 cm/yr (models) and ≥4.2 cm/yr (nature)) and trench velocity is always low (≤2.5 cm/yr (models) and ≤1.7 cm/yr (nature)) in the center of wide subduction zones (D_SE > 2200 km). Only in regions close to lateral slab edges (D_SE < 1000 km), be it for narrow or wide subduction zones, can the trench velocity exceed 4 cm/yr (models) and 6 cm/yr (nature) and can the subducting plate velocity go below 4 cm/yr (models) and 2 cm/yr (nature). In general, plate velocities, trench velocities and subduction partitioning are much more variable near slab edges than in the center of wide subduction zones owing to other parameters that affect subduction kinematics. We conclude that subduction kinematics can vary considerably along individual subduction zones and that the upper bound values for trench velocity and lower bound values for subducting plate velocity and subduction partitioning at individual subduction zone segments depend critically onD_SE.

Antarctic vertical motions revealed by GPS observations

Un paper en GRL sobre movimientos verticales de Antartida en respuesta a cambios en el espesor de hielo. Abstract follows:

Widespread low rates of Antarctic glacial isostatic adjustment revealed by GPS observations: Bedrock uplift in Antarctica is dominated by a combination of glacial isostatic adjustment (GIA) and elastic response to contemporary mass change. Here, we present spatially extensive GPS observations of Antarctic bedrock uplift, using 52% more stations than previous studies, giving enhanced coverage, and with improved precision. We observe rapid elastic uplift in the northern Antarctic Peninsula. After considering elastic rebound, the GPS data suggests that modeled or empirical GIA uplift signals are often over-estimated, particularly the magnitudes of the signal maxima. Our observation that GIA uplift is misrepresented by modeling (weighted root-mean-squares of observation-model differences: 4.9–5.0 mm/yr) suggests that, apart from a few regions where large ice mass loss is occurring, the spatial pattern of secular ice mass change derived from Gravity Recovery and Climate Experiment (GRACE) data and GIA models may be unreliable, and that several recent secular Antarctic ice mass loss estimates are systematically biased, mainly too high.

Model and data compared