Sandbox Experiment 8 (gentle dip, variable sand thickness) скачать в хорошем качестве

Sandbox Experiment 8 (gentle dip, variable sand thickness)

This is a model of an accretionary prism in a subduction zone. The colored sand (i.e. sediments) sits on top of sandpaper (i.e. subducting plate), which is pulled to the right as the crank is turned. This experiment uses variable thickness (3.5 - 4.5 cm) to represent sediments being eroded off of the overriding plate and deposited in the trench. The dip of the box is 2 degrees, similar to many accretionary prisms. As the crank is turned, the sandpaper moves to the right, but the sand is blocked by the wooden backstop. This causes the sand to deform. The colored layers allow you to see the details of the deformation: faults (offsets) and folds. The faults start close to the crank side and progressively propagate further out. Once a stable shape has been reached, the sandpaper slides beneath the sand without causing further internal deformation. The overall geometry and internal deformation produced in the model mimic the deformation in convergent zones between tectonic plates, like subduction zones. These structures develop over millions of years due to plates moving at millimeters per year. Faults store elastic strain energy as plates collide, and slip in sudden events, which we experience as earthquakes. Earthquakes in subduction zones can also produce tsunamis. Experiments like this one let us observe deformation in real time over minutes rather than millions of years, to understand the process of fault formation and deformation. This experiment was run by researchers studying Structural Geology at the Asian School of the Environment, Nanyang Technological University, Singapore. Instructions for building your own sandbox can be found at http://tinyurl.com/jsyhtm7. For more about structural geology teaching and research, visit my website: https://sites.google.com/site/juditha....