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The crust of the earth is in slow motion action, constantly being stretched or squeezed. The pressure on the rocks can deform or break them, causing folds or faults in the beds of rock. Folds mainly go up and down. The ones that go up are called anticlines, the ones that go down are called synclines. These features can be large enough to be hills and valleys in a mountain range, or can be squiggles seen in a hand-sized rock.
There are many different types of folds that can occur. A symmetrical fold is one in which the axial plane is vertical. An asymmetrical fold is one in which the axial plane is inclined. An overturned fold, or overfold, has the axial plane inclined to such an extent that the strata on one limb are overturned. A recumbent fold has an essentially horizontal axial plane. When the two limbs of a fold are essentially parallel to each other and thus approximately parallel to the axial plane, the fold is called isoclinal.
Many folds are distinctly linear; that is, their extent parallel to the axis is many times their width. Some folds, however, are not linear but are more or less circular in plan. A dome is such a fold that is convex upward; this means that its strata dip outward from a central area. A basin is a circular fold that is concave upward—i.e., the strata dip inward toward a central area. Chevron folds are a structural feature characterized by repeated well behaved folded beds with straight limbs and sharp hinges. Well developed, these folds develop repeated sets of v-shaped beds. Inter-limb angles are generally 60 degrees or less.
To claim this earth cache please email the answers to the following questions through our profile.
1. Suggest what type of fold can be found at the given coords and explain why you think this.
2. Estimate the widths of the largest and smallest beds.
3. Some of the cracks in the layers have been filled with a mineral, describe this mineral and what you think it is. (this can also be seen on the beach rocks under your feet!)
4. Describe the difference between the rock at beach level and the rock higher up the cliff and suggest a process that may be responsible for this difference.
Optional task - Take a picture of yourself near the area of the feature. This is not required to log the cache.
Placed with the kind permission of Natural England