Vein arrays are often composed of pull-aparts which are linked by shear fractures, good examples of which occur in the Lower Jurassic limestones of Somerset, southwestern England. Such pull-apart arrays have displacement-distance characteristics which are similar to fault zones, with maximum displacement (indicated by the largest pull-apart widths) near the centre of the array, and with displacement decreasing towards the tips. Pull-apart arrays usually die out into en echelon or pinnate veins. Evidence for pressure solution along the shear fractures which connect pull-aparts include their dark and braided nature, their obliquity to the displacement direction, the high dihedral angles (often > 90°) between conjugate shear fractures, and the dissolution of earlier structures. A range of geometries occurs, with varying relative amounts of veins and pressure solution being related to varying amounts of transtension or transpression. There is a general trend for an increase in the angle between vein segments and the shear fractures as contraction increases. There is therefore a trend for increased pressure solution on the shear fractures in more contractional arrays. The concentration of insoluble material along shear fractures has important implications for the mechanics and sealing of faults.

Volcanic eruptions are spectacular natural events that have piqued man's curiosity since prehistoric times. On the one hand they can be of great benefit to man, but on the other can cause great harm and thereby provide a major impetus to their study. Broader aspects make use of volcanoes as windows into the interior of the earth. Magma, molten rock, provides one of the major clues to the earth's origin and to the evolution of its mantle and crust. Our planet's hydrosphere and atmosphere - and thus the origin and evolution of life - owe their origin to degassing of the earth, a process largely accomplished by volcanic eruption. Periods of especially intense volcanic activity can affect climate and thus the world's flora and fauna. Volcanic rocks are the source material from which many sedimentary and metamorphic rocks are derived.

What is the quality of the sample and assay data? Am I confident enough in my data to be able to make a potentially costly decision? These are the types of questions which should be asked when dealing with assay data.

QGIS is a crossing point of the free and open source geospatial world. While there are a great many tools in QGIS, it is not one massive application that does everything, and it was never really designed to be that from the beginning. It is rather a visual interface to much of the open source geospatial world. You can load data from proprietary and open formats into spatial databases of various flavors and then analyze the data with well-known analytical backends before creating a printed or web-based map to display and interact with your results. What’s QGIS’s role in all this? It’s the place where you check your data along the way, build and queue the analysis, visualize the results, and develop cartographic end products. This learning path will teach you all that and more, in a hands-on learn-by-doing manner. Become an expert in QGIS with this useful companion. <...>