| dc.contributor.author | Ellis, Susan Marian. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:54Z | |
| dc.date.available | 1995 | |
| dc.date.issued | 1995 | en_US |
| dc.identifier.other | AAINN05266 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55061 | |
| dc.description | The processes involved when continents collide can often only be inferred from studies of rocks exposed at the surface of the Earth. To determine the forces which cause the deformation seen at the surface, we can use analytical and numerical models, where the behaviour of the lithosphere is simplified into a set of end-member styles. | en_US |
| dc.description | In this thesis, two possible end-member styles for convergent plate boundaries are investigated using simple analytical and numerical models, which represent the crust and/or lithosphere as a non-linear viscous thin-sheet. The thin-sheet approximation reduces the complexity of three-dimensional lithospheric behaviour to two (planform) dimensions. Use of the thin-sheet approximation restricts the study to large-scale plate boundary interactions. | en_US |
| dc.description | Using the models, differences for the length-scale of deformation seen at the surface are predicted for the two contrasting styles of forcing: (a) where the lithosphere deforms as one layer, and is indented from the side by a convergent plate of finite extent; and (b) where the crust detaches from the underlying mantle lithosphere, which subducts at the plate boundary. Style (a) is referred to as the side-driven model, and has already been used to explain large-scale continental convergent settings, such as the India-Eurasia collision. Style (b) is referred to as the basally-driven model, and has not previously been investigated using a thin-sheet tectonic model. | en_US |
| dc.description | The first part of this thesis develops analytical and numerical models for the basally-driven model, and shows that when crustal deformation is controlled by detachment and subduction of mantle lithosphere, the scale of the deformation can be parameterized in terms of a new scaling number, the Ampferer number. In contrast, length-scale predictions for the side-driven model depend on the lateral scale of the indenter. Predicted length-scale ratios for convergent vs. strike-slip settings are different for the two cases. A case with a combination of basal forcing and indenter mechanics is also investigated, and deforms over length-scales which depend on the strongest forcing parameter. | en_US |
| dc.description | The predictions of the two end-member styles are tested in a comparison with natural examples in the latter half of the thesis. On the basis of this comparison, neither end-member can be rejected as a candidate for deformation style. A further investigation for large amounts of convergence, indicates that a combination of indentation and basal forcing may best represent large-scale continental convergence. However, the large uncertainties in the model-data comparisons suggest that length-scale analyses by themselves cannot be used to distinguish first-order controls on mountain building, and that further direct measurements of deep lithospheric processes are required. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1995. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Geophysics. | en_US |
| dc.title | Continental convergence: Length-scales, aspect ratios, and styles of crustal deformation. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
