Browsing by Subject "ECUADOR"

Sort by: Order: Results:

Now showing items 1-2 of 2
  • Schütt, Jorina Marlena; Whipp, David Michael (2020)
    Strain partitioning onto margin-parallel thrust and strike-slip faults is a common process at obliquely convergent plate margins, leading to the formation and migration of crustal slivers. The degree of strain partitioning and rate of sliver migration can be linked to several factors including the angle of convergence obliquity, the dip angle of subduction, frictional coupling between the plates and the strength of the upper plate, among others. Although these factors are known to be important, their relative influence on strain partitioning is unclear, particularly at natural margins where the factors often vary along strike. Here we use a 3-D mechanical finite-element model to investigate the relationship between continental crustal strength, the convergence obliquity angle, the subduction angle, and strain partitioning in the Northern Volcanic Zone (NVZ) of the Andes (5 degrees N-3 degrees S). In the NVZ the subduction dip and obliquity angles both vary along strike, weaknesses in the continental crust may be present in suture zones or regions of arc volcanism, and strain partitioning is only observed in some regions. Thus, it is an ideal location to gain insight in which of the factors have the largest influence on deformation and sliver formation in the upper plate. Our numerical experiments confirm that a moderately high obliquity angle is needed for partitioning and that a continental crustal weakness is also required for movement of a coherent continental sliver at rates similar to geodetic observations from the NVZ. In contrast, the subduction dip angle is only of secondary importance in controlling strain partitioning behavior. Key Points Factors influencing formation of continental slivers investigated using 3-D numerical models of finite-width oblique subduction systems Model results indicate that convergence obliquity and the presence of weak zones in the upper plate are key to formation of well-defined slivers Model predictions are in good agreement with geodetic observations of sliver motion in the Northern Volcanic Zone of the Andes
  • Hohenthal, Johanna Maaria; Räsänen, Marinka; Minoia, Paola (2018)
    Environmental resource management policies worldwide have long insisted on the need to involve local communities and their diverse ecological knowledges in management planning and decision-making. In SubSaharan post-colonial countries, however, formal resource management is still largely dominated by bureaucratic governance regimes that date back to colonial power structures and that rely mainly on professional or formal knowledge. In this study, we use a political ecology approach to analyze disputes over eucalyptus plantations in the Taita Hills, Kenya. The approach recognizes the plurality of socially constructed and powerladen perceptions of environmental resources. We found that local people regard eucalyptus plantations not only as a threat to local water resources but they also highlight historical injustices and the loss of control over, and cultural relationships to their land. Bureaucratic resource management institutions, however, support the planting of eucalyptus to meet national demands for commercial forestry. Management officials also plead a lack of "valid" evidence for the negative impacts of eucalyptus on local water resources, diverting attention away from the formal environmental governance system which has unequal sharing of benefits, unclear policies, and internal incoherence. Recognition of historically rooted asymmetries of knowledge and power provides a step towards social transformation, ending a long-standing reproduction of subalternity, and promoting environmental justice and pluralism in decision-making. Keywords: bureaucratic knowledge; environmental justice; eucalyptus; Kenya; knowledge asymmetries; local ecological knowledge; political ecology; resource management