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The large scale structure of the earth is caused by which are explained using and descriptions. While “geodynamic processes” are understood to include a large variety of and the term is used quite loosely, the methods of their involve well defined fields. descriptions are involved with distribution of energy in our planet, typically expressed in terms of heat and temperature. descriptions describe movements using velocities, strains and strain rates. descriptions indicate how stresses and forces behave.

In this chapter we repeat basic aspects of the theory of plate tectonics. In the first part of the chapter a summary of the history of the plate tectonic model is presented and some basic principles how to describe it are discussed. Some arguments that suggest why plate tectonics may work are also presented. In the second part of this chapter we discuss the layered structure of the earth and the geographic distribution of lithospheric plates. We will also use this chapter to introduce the terminology that is used in the remainder of the book. As such, the chapter is meant as a basis for all following chapters.

In this chapter we discuss geodynamic processes that may be described with the units of energy or temperature. This general theme is an obvious starting point in geodynamics, as so many properties of rocks that may be observed in the field are a strong function of temperature, for example the formation of metamorphic parageneses or the mechanisms with which rocks deform.

In this chapter we discuss the position, shape and the motion of rocks. In short: geodynamic processes measured in . This includes the discussion of strain and ventures therefore a bit into the field of structural geology. However, mostly we shall discuss processes like the elevation of mountain ranges, and the depth of the oceans, as well as the of such parameters: kinematics. We begin with a consideration of the basics of strain. Our summary remains brief and the interested reader is referred to a number of excellent textbooks in the field of structural geology (Pollard and Fletcher 2006; Ramsay and Huber 1983; 1987; Ramsay and Lisle 2000; Twiss and Moores 1992; Pluijm and Marshack 1997).

In this chapter we discuss the forces involved in geodynamic processes. Knowing a bit about forces is a great tool for the field geologist to test field observations. Let us consider an example: A field geologist finds folds and thrusts in a Precambrian terrain that he or she interprets to have formed as the consequence of crustal shortening. Strain analysis shows that 80% shortening occurred and the geometry of shortening indicates that this resulted in fourfold thickening of the crust. He therefore further infers (using the principle of isostasy) that - at the time - a mountain range of some 15 km elevation existed above the metamorphic terrain. This interpretation is consistent with the field observations, but it has no independent test. In this particular example we could argue that we have no knowledge of any present day mountain range that is this high and that, therefore, this interpretation is unlikely. However, in many less obvious examples there are no direct analogies and the resulting model is - albeit perfectly imaginable and fully consistent with field observations - wrong. One way to provide an independent test of such models is to make a rough estimate of the forces involved. In the next chapters we want to perform such estimates. In order to do so, it is necessary to commence with a brief repetition of the basics of stress and strain. For more details on the basics the interested reader is referred to a range of excellent text books on the subject.

This chapter is the first of two chapters in which we integrate the information of the previous three chapters into “real” tectonic models. The first two thirds of this chapter are dedicated to the description of continents in extension and in collision. In the last third of this chapter we touch upon a range of interesting and currently very topical geodynamic problems.

One of the basic data sets used by geologists for the geodynamic interpretation of a metamorphic terrain is the spatial and temporal evolution of pressure , temperature and deformation that the rocks experienced: the metamorphic evolution of the rocks. Data on the metamorphic evolution are particularly important when interpreting ancient orogens where it is impossible to measure many other parameters directly (e.g. surface elevation, surface heat flow, gravity etc.). The relative evolution of pressure, temperature and deformation may well be illustrated as curves in -space. Such curves are called -paths or -paths, if the path is also labeled for deformation events and time. As the interpretation of metamorphic rocks is so crucial to any geodynamic interpretation performed by a field geologist, we dedicated it here its own chapter. For detailed treatment of thermodynamics underlying all petrological studies of -paths we recommend: Anderson and Crerar (1993) or: Atkins (1994). For more petrologically oriented texts with geodynamic applications we recommend: Spear (1993) or: Spear and Peacock (1989).