Salt Glaciers
Where salt flows out of a diapir (salt plug) above sea level it flows gravitationally in the direction of highest dip. In dry regions, such as Iran, the flow occurs … Read More
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Columnar Jointing
In many respects, sills closely resemble buried lava flows. Both are tabular and can extend over a wide area, and both may exhibit columnar jointing. Columnar jointing occurs when igneous … Read More
Strike and Dip
Sedimentary rock units, because they are usually deposited in horizontal layers, are most useful when studying rock deformation. If the sedimentary rock layers are horizontal, geologists infer that the area … Read More
Principle of Cross-Cutting Relationships
Figure 1 shows layers of rock that have been offset by a fault, a fracture in rock along which displacement occurs. It is clear that the strata must be older … Read More
Anticlines and Synclines
The two most common types of folds are anticlines and synclines (Figure 1). Anticlines occur when compressional stresses squeeze sedimentary layers into arch-like folds. These upfolded structures are sometimes spectacularly … Read More
Hydraulic Fracturing
In some shale deposits, there are significant reserves of natural gas that cannot naturally leave because of the rock’s low permeability. The practice of hydraulic fracturing (often called fracking) shatters … Read More
Slope support
Slope support Retaining walls: common practice and successful on small slopes and cut faces, but not on larger slopes. Large unstable slopes are not easily retained; it is difficult and … Read More
Describing and Classifying Soils
The factors controlling soil formation vary greatly from place to place and from time to time, leading to an amazing variety of soil types. These vertical differences, which usually become … Read More
The Richter and Mercalli Scales
Seismic waves are characterized by their wavelength and amplitude. Shorter-wavelength and higher-amplitude waves are the most destructive (Figure 1). Earthquakes happen all the time everywhere on Earth. Most are so … Read More
Piezometer
A piezometer is either a device used to measure liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity, or a … Read More