As hiking and caching this section of the RVT for the new caches published this am...seen this awesome site as heading back to vehicles....No, I did not get any FTF's here, as beans&frank, again, planned an earlier start!!! Have to be on the ball to beat him... Did meet up with Frank & PA Ridgerunners at the last cache, they had the same idea, but no luck for them either.....then we all had a great time visiting and hunting caches on return to vehicles...
Anyway, as you hike along the RVT, you will see many areas of rock showing through the vegetation... many areas of layering and nice holes and small openings to hide a geocache... At coordinates you will see a nice samplings of rock folds... Human development activities and erosion lead to exposure of these rock folds...
Rock Folds - a rock layer that was, originally, formed horizontally, then Earth movement caused it to fold… they vary in size, from microscopic crinkles to mountain-sized folds… they can occur singly as isolated folds or in multiple of folds of different sizes & types…multiple folds as in a train are called a fold belt..
After reading and checking rock layers (all questions can be answered while walking on the trail), please message me answers to these questions: and as pics are great, please no spoilers...
1. From the direction of parking area at St. Charles Rd, label the visible folds in this rock belt.
2. Now label each if they are symmertical or asymmetrical, please give reasoning.
3. How long in feet is the lenght of this visible rock belt?
Folding - rock often deforms, from Tetonic forces, in such a way that it bends or curves instead of breaking…These forces, such as pressure and high temperature, occur over time to allow for bending & folding, and not fracturing… Folds are most visible in rocks that contain layering..
3 types of folds:
- Monocline - has a slight bend in rock layers.
- Anticline - rock layers that convex up into an arch-like shape, with the limbs dipping away from the center.. About 80 percent of world’s petroleum has been found in anticlinal traps..
- Syncline is the opposite of anticline - the layers bend or warp downward.. Remember - syn makes you grin..
Structure of a fold -
- Upfold ia an anticline.
- Downfold is a syncline.
- Crest line - imaginary line joining highest points along the fold.
- Flanks - are the limbs of a fold, the sides of a fold.
- Axis - central line from which the rock strada did away in opposing directions.
5 main types of folding, due to degree of folding:
- Symmetrical fold -two limbs are of equal steepness
- Asymetrical fold - one limb is steeper than the other
- Overfold - one limb is pushed over the other
- Recumbent fold - two limbs are nearly parallel, more horizontal.
- Overthrust fold - compressional force is so great that the rock strata are broken and slide over the other
References:
Wikipedia - Fold(geology), Anticline
Geologic Structures…ur ses.lumenlearning.com - Tetonic Forces
Reading Folds…uses.lumenlearning.com - Crustal Deformation