Metamorph;c processes have been taking place on a massive scale throughout the Earth's history, and have affected the bulk of the rocks now present in the crust. Despite this, they are not as well understood as sedimentary or volcanic processes, because metamorphism can scarcely ever be observed directly, and the study of metamorphic rocks is instead based on observation, inference and logic, founded in relatively simplistic experimental studies and the basic principles of chemistry and physics

Morphology

Diatoms are microscopic unicellular algae. Whatever the shape or size of the cell, it consists of the same basic parts: the nucleus, cytoplasm, plasma membrane, and the cell wall.

1.1. Structure of the Cell Wall

Emphasis in this Introduction is placed on the structure of the diatom cell wall, as opposed to the living contents, as, in the main, interest in diatom study is directed toward the structure and microstructure of the cell wall. Classification of diatoms and their identification pertinent to many areas of investigation is based on the structure of, and markings on the cell wall as revealed by the light microscope (LM). It is therefore imperative that the student of diatoms possesses a good basic knowledge of that structure and the terminology associated with it. <...>

As Earth' s crust is the most accessible part of our planet, a wealth of information on its structure and composition is available from geological observations and geophysical measurements. Its shape and composition today are, however, the result of processes occurring at different scales in time and space, rendering study of the crust a complex and challenging undertaking. Field observations and seismic data, for example, confront us with the present day structures and must, for an in-depth understanding of their origin, be reconciled with the processes of deformation that created them. Reconstructing these processes in the past is commonly hindered by lack of continuous outcrop, limited depth resolution and little to no constraints on time. Analogue and numerical models may help improve our understanding of crustal-scale processes through their ability to simulate the birth and evolution of deformational structures at different scales. In this context, the link between theory and observations makes modelling a fundamental tool for the study of processes that alter the Earth's crust. <...>

For the analysis of spatially distributed data, a fundamental aspect is first considered: can the data be interpolated, or are they of such a type that an interpolation between two values measured at different locations makes no sense?