14. A(n) is a circular or oval fold in which the strata are warped in age downwa

Question

14. A(n) is a circular or oval fold in which the strata are warped in age downwardly in the center and the beds on the flanks are than the strata in the interior. 15. An episode of mountain building is known as a(n) 16. Each half of a fold is known as a(n) The type of strain that occurs depends not only on the kind of stress applied, but also on the: a amount of pressure and degree of temperature. b. rock type. c. duration of the stress 18. A fold is the result of deformation 19. A simple bend or flexure in an otherwise horizontal rock layer is called a(n) 20. Small accreted lithospheric blocks of foreign origin that differ completely from the rocks in surrounding regions are called 21. Volcanic island arcs are characteristic of which type of convergent plate boundaries? a. continental-continental b. continental-oceanic d. continental-oceanic AND oceanic-oceanic e. continental-continental; continental-oceanic AND oceanic-oceanic 22. At the San Andreas fault, the Pacific Plate is moving northwest relative to the southeast moving North American Plate. Therefore, movement along the San Andreas is: a. compressional b. tensional c. right-lateral d. left-lateral e. vertical 23. Rocks that are tilted were deposited 24. Sedimentary rocks that are now tilted were deposited 25. Most folding of rocks occurs near the surface. True/False

Explanation / Answer

14. Basin, older

Explanation : A basin is a circular or oval fold in which the strata are warped downwardly in the center and the beds on the flanks are older in age than the strata in the interior. It is actually a form of a syncline where the younger beds occur at the core of the fold surrounded by successively younger beds/strata's.

15. Orogeny.

Explanation : An orogeny is an episode of mountain building that describes the entire time period involved in the mountain building processes. Examples : Caledonian Orogeny, Alpine orogeny etc.

16. Limb.

Explanation : Limbs are the portion of a fold extending from the hinge portion to the inflection points on either flank of a fold.

17. (c) duration of the stress.

Explanation : The type of strain that occurs depends not only on the kind of stress applied but also on the time or the duration of the application of the stress. Stress applied for a longer duration will lead to a greater strain.

18. Plastic

Explanation : Plastic deformation is a change in shape of a solid body or a permanent deformation without fracture under the effect of an applied stress/strain. This is exactly what happens incase of a fold.

19. Monocline.

Explanation : A monocline is a step-like bend in a strata. It may also be defined as a simple bend or flexure in an otherwise horizontal rock layer.

20. Terrains.

Explanation : Terranes are fragments of crustal material which forms small accreted lithospheric blocks of foreign origin that completely differs from the rocks in its surrounding regions.

21.(c) Oceanic - oceanic.

Explanation : Volcanic island arcs form when an oceanic lithospheric plate subducts beneath another oceanic lithospheric plate.

22. (c) Right-lateral.

Explanation : If the Pacific plate moves northwest relative to the North American plate which moves southeast, and I as an observer stand on either side of the fault plane, the right block(Pacific plate) appears to move towards me which means it is right lateral movement.

23. Horizontally and then they were tilted into their present orientation.

Explanation : Rocks that are tilted wre deposited horizontally. This can be explained by the principal of horizontality.

24. Horizontally.

Explanation : According to the principal of horizontality, sedimentary rocks are originally deposited horizontally which are then later folded and tilted.

25. False.

Reason : Most folding of rocks occur at greater depths in the earth's interior where the temperature and pressure conditions are extremely high and the rocks behave and deform plastically resulting in the formation of folds.

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