Plate N Sheet 4.10.02 Keygenl

By the early 1970s, the basics of plate tectonics were known. Although much understanding remained to be gained, as a topic of research, plate tectonics no longer defined the forefront of earth science. Not only had it become a foundation on which to build, but also the methods used to reveal it became tools to take in new directions. For me as a seismologist studying earthquakes and active processes, the deformation of continents offered an obvious topic to pursue. Obviously examining the deformation of continents and ignoring the widespread geologic evidence of both ongoing and finite deformation of crust would be stupid. I was blessed with the opportunity to learn from and collaborate with two of the best, Paul Tapponnier and Clark Burchfiel. Continental deformation differed from plate tectonics both because deformation was widespread but more importantly because crust shortens (extends) horizontally and thickens (thins), processes that can be ignored where plate tectonics - the relative motion of rigid plates - occurs. Where a plate boundary passes into a continent, not only must the forces that move plates do work against friction or other dissipative processes, but where high terrain is created, they must also do work against gravity, to create gravitational potential energy in high terrain. Peter Bird and Kenneth Piper and Philip England and Dan McKenzie showed that a two-dimensional thin viscous sheet with vertically averaged properties enabled both sources of resistance to be included without introducing excessive complexity and to be scaled by one dimensionless number, what the latter pair called the Argand number. Increasingly over the past thirty years, emphasis has shifted toward the role played by the mantle lithosphere, because of both its likely strength and its negative buoyancy, which makes it gravitationally unstable. Despite progress since realizing that rigid plates (the essence of plate tectonics) provides a poor description of continental

Recent numerical studies of convection in the earth's mantle have included various features of plate tectonics. This paper describes three methods of modeling plates: through material properties, through force balance, and through a thin power-law sheet approximation. The results obtained are compared using each method on a series of simple calculations. From these results, scaling relations between the different parameterizations are developed. While each method produces different degrees of deformation within the surface plate, the surface heat flux and average plate velocity agree to within a few percent. The main results are not dependent upon the plate modeling method and herefore are representative of the physical system modeled.

Download File

In northern Taiwan, contraction, transcurrent shearing, block rotation and extension are four essential tectonic deformation mechanisms involved in the progressive deformation of this arcuate collision mountain belt. The neotectonic evolution of the Taiwan mountain belt is mainly controlled not only by the oblique convergence between the Eurasian plate and the Philippine Sea plate but also the corner shape of the plate boundary. Based on field observations and analyses, and taking geophysical data (mostly GPS) and experimental modelling into account, we interpret the curved belt of northern Taiwan as a result of of contractional deformation (with compression, thrust-sheet stacking & folding, back thrust duplex & back folding) that induced vertical extrusion, combined with increasing transcurrent & rotational deformation (with transcurrent faulting, bookshelf-type strike-slip faulting and block rotation) that induced transcurrent/rotational extrusion and extension deformation which in turn induced extensional extrusion. As a consequence, a special type of extrusional folds was formed in association with contractional, transcurrent & rotational and extensional extrusions subsequently. The extrusional tectonics in northern Taiwan reflect a single, albeit complicated, regional pattern of deformation. The crescent-shaped mountain belt of Northeastern Taiwan develops in response to oblique indentation by an asymmetric wedge indenter and opening of the Okinawa trough at plate corner.

In northern Taiwan, contraction, transcurrent shearing, block rotation and extension are four essential tectonic deformation mechanisms involved in the progressive deformation of this arcuate collision mountain belt. The neotectonic evolution of the Taiwan mountain belt is mainly controlled not only by the oblique convergence between the Eurasian plate and the Philippine Sea plate but also the corner shape of the plate boundary. Based on field observations and analyses, and taking geophysical data (mostly GPS) and experimental modelling into account, we interpret the curved belt of northern Taiwan as a result of of contractional deformation (with compression, thrust-sheet stacking & folding, back thrust duplex & back folding) that induced vertical extrusion, combined with increasing transcurrent & rotational deformation (with transcurrent faulting, bookshelf-type strike-slip faulting and block rotation) that induced transcurrent/rotational extrusion and extension deformation which in turn induced extensional extrusion. As a consequence, a special type of extrusional folds was formed in association with contractional, transcurrent & rotational and extensional extrusions subsequently. The extrusional tectonics in northern Taiwan reflect a single, albeit complicated, regional pattern of deformation. The crescent-shaped mountain belt of Northeastern Taiwan develops in response to oblique indentation by an asymmetric wedge indenter, retreat of Ryukyu trench and opening of the Okinawa trough.

Provides background information on the layers of the earth, the relationship between changes on the surface of the earth and its insides, and plate tectonics. Teaching activities are included, with some containing reproducible worksheets and handouts to accompany them. (TW)

The region of inland East Antarctica between Casey and Davis stations (Wilkes Land to Princess Elizabeth Land) is one of the least investigated parts of the continent with respect to its tectonic and solid Earth structure. This is difficult to estimate because the conjugate margin in plate reconstructions has been lost in the collision between India and Eurasia. The region is also host to some of the greatest uncertainties in Antarctica in glacial-isostatic adjustment observations and models, and where the contribution of heat from underlying rocks is difficult to estimate due to the limited available rock samples. We investigate the solid Earth structure and its interactions with the East Antarctic ice sheet through a new campaign including GPS and seismic instrument deployments, and field measurements to constrain ice retreat history. This presentation provides an overview of the new, multi-year Casey-Davis Glacial Isostatic Adjustment campaign including station locations and deployment progress. The campaign is being supported by Australian Antarctic Division and uses a combination of fixed-wing and helicopter support to access station locations in both coastal locations and the continental interior. A primary long-term objective of the campaign is to remove bias from estimates of East Antarctica's contribution to past and present sea level changes. We also seek to better constrain the geothermal influences on the East Antarctic ice sheet. The GPS determinations of vertical plate motion and the detailed seismic structure await data downloads in future field seasons, however, we are able to present new findings from preliminary studies. We show candidate ancient tectonic reconstructions for this part of East Antarctica and make use of our knowledge of structure of continental regions with a similar evolution to infer the likely structures for the Casey-Davis region. We add these new constraints to the structure currently inferred from a very small number of

The Education and Outreach program at UNAVCO has developed free instructional materials using authentic high-precision GPS data for secondary education and undergraduate students in Earth science courses. Using inquiry-based, data-rich activities, students investigate crustal deformation and plate motion using GPS data and learn how these measurements are important to scientific discovery and understanding natural hazards and the current state of prediction. Because this deformation is expressed on Earth's surface over familiar time scales and on easily visualized orders of magnitude, GPS data represent an effective method for illustrating the geomorphic effects of plate tectonics and, in essence, allow students to 'see' plates move and volcanoes deform. The activities foster student skills to critically assess different forms of data, to visualize abstract concepts, and to evaluate multiple lines of evidence to analyze scientific problems. The activities are scaffolded to begin with basic concepts about GPS data and analyzing simple plate motion and move towards data analyses for more complex motion and crustal deformation. As part of assessment, students can apply new knowledge to explore other geographic regions independently. Learning activities currently include exploring motion along the San Andreas Fault, monitoring volcano deformation and ground movement at the Yellowstone Caldera, and analyzing ground motion along the subduction zone in the Cascadia region. To support educators and their students in their investigations, UNAVCO has developed the Data for Educators portal; _outreach/data.html. This portal provides a Google-map displaying the locations of GPS stations, web links to numerical GPS data that illustrate specific Earth processes, and educational activities that incorporate this data. The GPS data is freely available in a format compatible with standard spreadsheet and graphing programs as well as visualization and

d0d94e66b7