geos3003- The Dynamics of Continents & Basins


	Isostasy and gravitational forceS... NB: Individual practical reports are due next week and will be collected at the beginning of the practical class. Should you hand-in your report later do not forget to write the date at which the report was handed in on the front page, without this information I will have to use the date at which we collected the report. This is a report, not an answer sheet, so please give enough details, including the aim of the exercise you try to solve, so the assessor can understand your solution and the procedure you follow. Hand written reports are acceptable, but please write clearly.
	Practical 2: Isostasy and gravitational forceS. - You can download a PDF version of this Pract: The purpose of this practical to get up close and personal with the theory of isostasy and the concept of gravitational force. These are key concepts that underpin the dynamics of mid-oceanic ridges, rift-basins, mountain belts and orogenic plateaux. Outcomes: To develop a deeper understanding of the theory of isostasy and how it controls the surface elevation of plates. To develop a deeper understanding of the dynamic of orogenic plateaux. To be able to evaluate the magnitude of the gravitational forces acting between two lithospheric columns of contrasted elevations and/or density structures. Generic skills: Problem solving ability, computational skills, and analytical skills. Assumed background knowledge: Basic knowledge on isostasy, lithostatic pressure and gravitational potential energy (check out your lecture notes) and Year 12 Mathematics. Tools you may want/need to use: MatLab or LiveMath, Excel spreadsheet, calculator... Reading: Turcotte & Schubert: Geodynamics Submission details Individual report due next week at the beginning of the practical class. Should you hand-in your report later, please do not forget to write the date of return on the front page. Some fundamentals On the theory of isostasy: The theory of isostasy assumes that there is a depth called "the compensation level" under which the stress is lithostatic (isotropic stress) therefore only related to the weight of the rock column above. In other terms there is no lateral variation of lithostatic pressure (also called confining pressure) along a given gravitational equipotential surface. It is isostasy that dictates the elevation of lithospheric plates. On the gravitational potential energy and the gravitational force: Above the compensation level, lateral variations of density produce lateral contrasts in Gravitational Potential Energy (GPE) responsible for an horizontal force called the gravitational force (Fg, a volume force). The gravitational potential energy of a column of lithosphere corresponds to vertical integration, down to the compensation level, of the lithostatic pressure profile. The gravitational force per unit length (Nm^-1) that two lithospheric columns apply to each other is equal to the difference in their GPE.

Submission details Individual report due next week at the beginning of the practical class. Should you hand-in your report later, please do not forget to write the date of return on the front page.

Submission details
Individual report due next week at the beginning of the practical class. Should you hand-in your report later, please do not forget to write the date of return on the front page.