(d) Once this information is obtained, the geologist can employ the principles of geometry and trigonometry to determine the orientation of the axial plane and also whether the fold plunges. Folds, joints and faults are caused by stresses. 5. (b) Fig. 3. 3. Folds are bends in rocks that are due to compressional forces. Source: USGS, 1970. Tethys geosyncline. • Can be at any scale from outcrop to map scale. FOLDS, FAULTS AND GEOLOGIC MAPS Objectives •Define three types of stress. 9. If you are at an office or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or infected devices. Figure 10.9: Folds are a result of ductile deformation of rocks in response to external forces. If the axis is not horizontal, the structure is said to be a plunging fold. This is known as ductile deformation and the rock is said to behave plastically. 10.6a: Compressive forces generate folding and faulting as a consequence of shortening. • Figure 10.7: Rocks are defined as brittle or ductile on the basis of the way they are deformed by forces. Everyday low … Larger faults are mostly from action occuring in earth's plates. Figure 10.7: Another factor that determines how a rock deforms is confining pressure, which is like the pressure you feel when you dive deep underwater. Rock exposures become progressively younger towards the axis of synclines. Figures 10.10 & 10.11: The two sides of a fold are referred to as limbs. For basins and domes, strata exposed at the surface form concentric circles around a central point (Figure 10.16). •Define and describe synclines, anticlines, and other types of folds. also reveal differences in the joint systems at limb and hinge positions on large folds or different distances from large faults. In the nineteenth century, the predominant theory was that since its hot, molten formation, the Earth has been slowly cooling and thus shrinking and collapsing, like the skin of a drying apple, which produces mountain-building structures such as faults and folds. 10.7b: When an external force is applied to buried rocks under low confining pressure, such as near the surface of the earth, the rock typically deform by simple fracturing. Rock bands appearing on one side of the fold axis are duplicated on the other side. 4. CHAPTER 10: Folds, Faults and Rock Deformation. Folds generally occur at great depths in the earth’s crust where the rock layers are exposed to high temperatures and pressures. The ramps are fault sections climbing through the stratigraphic sequence, typically at around 30° to the horizontal, across stiff, competent layers. Introduction • Structural geology is the study of factors such as origin, occurrence, classification, type and effects of various secondary structures like folds, faults, joints, rock cleavage and are different from those primary structures such as bedding and vesicular structure, which develop in rocks at the time of their formation. • The folds themselves may be folded and they are often recumbent. Folds form under … 7. Under similar confining pressures, halite (rock salt) is more susceptible to ductile deformation than is granite, which will more likely fracture. 5. 1. They are easily visualized by the loss of horizontality of the strata. Mob- +919764484757, Email- vyanky.g@gmail.com 3. •Define cratons and orogens. 2. The rock will contort and change shape without fracturing. Figure 10.14: When folds plunge into the earth, they essentially disappear from the surface. 1. 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