1.0 OBJECTIVE To plot ground profile and rock formations from geological map – inclined beddings.
2.0 LEARNING OUTCOMES a)
Students able to plot subsurface profile.
b)
Students able to understand the geological structure in subsurface profile.
c)
Students able to understand a history of the geological area.
4.0 EQUIPMENT AND MATERIALS 1. Geological Map ( Map 7 – Appendix B ) 2. Graph paper/drawing paper - A4 size 3. Ruler 4. Pencils 5. Colour pencils (optional) 5.0 PROCEDURE 5.1 Plot the cross-section with the horizontal and vertical scales accordingly to the scale of the geological map on a piece of graph paper or blank sheet. Refer Figure 1.1. The vertical scale is normally exaggerated to improve visibility of the profile. 5.2 Draw a line to join the line of cross-section on the map, says A - B. 5.3 Using a blank piece of paper, mark the points of intersection accordingly between the lines with the contours respective to its heights. 5.4
Transfer the points to the cross-section profile respective to the heights of the
contours. 5.5 Join the points to form the profile of the ground elevation. 6.0 RESULT AND ANALYSIS By referring to Map 7, Highlights the rock boundary to focus for determination of strike line. Select two pints within the marked boundary of similar heights. Draw the line between the two points to indicate the first strike line. Its value corresponding to two value of the contour. Select another point (of ascending @ descending contour value). Draw a line that touches the parallel the select point to the first strike line. Measure the distance (say, d1) cut at right angles to the parallel lines. Determine the angle of dip of the fold. Similarly, repeat similar procedure to the other wings of the fold. Identify the thickness of the outcrop.
7.0 QUESTIONS Explain types of fold (with the aid of diagram) and discuss how this structure occurred. Type of fold are :
Types of folds and their axial planes. a. Monocline : Are folds in which horizontal or gently dipping bed are modified by simple steplike bends.
Monoclines may be formed in several different ways (see diagram) By differential compaction over an underlying structure, particularly a large fault at the edge of a basin due to the greater compactibility of the basin fill, the amplitude of the fold will die out gradually upwards e.g. [1] By mild reactivation of an earlier extensional fault during a phase of inversion causing folding in the overlying sequence. As a form of fault propagation fold during upward propagation of an extensional fault in basement into an overlying cover sequence. As a form of fault propagation fold during upward propagation of a reverse fault in basement into an overlying cover sequence.
b. Anticline
: Up-arched rocks in which the older rocks are in the center and the younger
rocks are on the flanks. In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships (i.e. younging direction) between various strata are unknown, the term antiform must be used. On a geologic map, anticlines are usually recognized by a sequence of rock layers that are progressively older toward the center of the fold because the uplifted core of the fold is preferentially eroded to a deeper stratigraphic level relative to the topographically lower flanks. The strata dip away from the center, or crest, of the fold. If an anticline plunges (i.e., is inclined to the earth's surface), the surface strata will form Vs that point in the direction of plunge. Anticlines are typically flanked by synclines although faulting can complicate and obscure the relationship between the two. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. c. Syncline
: Folded downwards in which the younger beds in the center and the older
rocks on the flanks diagram of folds. In structural geology, a syncline is a downwardcurving fold, with layers that dip toward the center of the structure. A synclinorium is a large syncline with superimposed smaller folds. On a geologic map, synclines are recognized by a sequence of rock layers that grow progressively younger, followed by the youngest layer at the fold's center or hinge, and by a reverse sequence of the same rock layers on the opposite side of the hinge. If the fold pattern is circular or elongate circular the structure is a basin. A notable syncline is Wyoming's Powder River Basin. Folds typically form during crustal deformation as the result of compression that accompanies orogenic mountain building. A spectacular example of a perched syncline, the highest in Europe, is Saou, in the Alpine foothills of south-eastern France.
8.0 CONCLUSION Conclude your results especially by rate its effect on outcrop layer in relation to the civil engineering or construction industry etc. When the folds are formed from tectonic plate movement which happened thousand or maybe million years ago, there were different types of rock in the layer of folds and it will cause the site which not in the stable condition. Just as thrusts faults are clearly influenced by the mechanical properties of different rock-types, so are folds. It is because every layer of the rocks have different strength properties. It's common in fold to find that sandstone and limestone layers maintain their thickness when traced through folds, whereas shales and evaporites are strongly thickened in fold hinges. Therefore when there structure built in folds area, it will facing settlement and maybe collapse when the settlement is high or maybe when the plate moving. Base on the experiment that we’ve been analyse, we found that there is four categories of faults such monocline, anticline, syncline, overturned anticline and syncline. When the folds are formed by the earth quack, since happened thousand or maybe million years ago, there were different types of rock in the folds and it will cause the site is not in the stable condition. Therefore when there structure on the visit it will be easy facing settlement and it will be collapse when the settlement is high. Not all faults intersect the surface, object maybe offset or the ground maybe cracked, or raised or lowered. We call it a rupture of the surface by faults or ‘faults scraps’ and identifying scraps as is importing task for assessing the seismic hazard in any region.
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