Notice that in the block diagrams of the folds we have seen so far the beds in t

Question

Notice that in the block diagrams of the folds we have seen so far the beds in the side cross-sections are horizontal. This is because in all these folds the fold axis is horizontal and the edges of beds parallel to the axis (which is also parallel to the strike of the beds) will appear to be horizontal as well. If it's not clear what a fold axis is, refer to your textbook or repeat the first paper folding you did. Done correctly, this will show that the upper surface of the fold in the center, which coincides with the fold axis, is parallel to the horizontal surface of the table. Not surprisingly, folds with a horizontal fold axis are called horizontal folds, but it is also possible to produce folds where the axis is not horizontal. These are called plunging folds because they fold axes appear to dive into the Earth's surface rather than lie parallel to it. You can also simulate a plunging fold with a piece of paper. Make the horizontal fold as before, then rotate your wrists toward you or away. Notice that the upper surface of the fold now angles toward the table top. Use the painted models of plunging folds (blue, orange, green, and yellow) to help you with the following questions. Figures 12 and 13 are block diagrams of plunging folds, one a syncline and one an anticline. The beds In each are marked from A. the oldest, to F, the youngest. From what you know about the location of the youngest and oldest beds In mops of folds, determine which figure (12 or 13) is a plunging anticline and which is a plunging syncline, then draw the FRONT cross-section of each. Use the block models to help you. Notice that In the map view the outcrop patterns taper to a "nose". Again, refer to the wooden models, and see if you can tell which direction the nose points, toward the plunge direction or away from it. (The angle of the beds on the side of the model is the same as the plunge angle.) In which direction does the nose of the syncline point-IN THE DIRECTION OF PLUNGE I or OPPOSITE THE PLUNGE DIRECTION? Notice that if you turn over the model tor the plunging syncline it becomes a plunging anticline. Which way does the nose of the anticline point-IN THE DIRECTION OF PLUNGE/or OPPOSITE THE PLUNGE DIRECTION?

Explanation / Answer

Answers

17. Figure 12 is a plunging anticline and figure 13 is plunging syncline

18. The nose of the synclines points in the opposite direction of the plunge

19. If plunging syncline turned into plunging anticline, then the nose of the plunge points in the direction of the plunge

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