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
Principle of Inclusions
Sometimes inclusion can aid in the relative dating process. Inclusion is a fragment of one rock unit that have been enclosed within another. The basic principle of inclusion is logical … Read More
Standard penetration test
Procedure The test uses a thick-walled sample tube, with an outside diameter of 50.8 mm and an inside diameter of 35 mm, and a length of around 650 mm. This … Read More