Chapter 10 Assignment (1) PDF

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Structural Geology: a study of Earth’s architecture...

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/Chapter 10 Assignment_________________________________________________________ Structural Geology: a study of Earth’s architecture Deformation 1.Deformation is a general term that refers to all changes in the original _ Form and/or __size____ of a rock body 2.Most crustal deformation occurs along __Plate_________ ____Boundaries__________ 3.Deformation involves ____Force____ which tends to put stationary objects in motion or change the motions of moving objects. 4. __Stress____ is defined as the amount of force applied to a given area. 5. There are three types: a. _Compressional________ ___Stress___ tends to shorten a rock body and occurs at convergent plate boundaries. b. _Tensional______ ___Stress____ tends to elongate or pull apart a rock unit and most commonly occurs at divergent plate boundaries. c. _Shear Stress__ tends to occur at transform plate boundaries and involves a motion similar to the slippage that occurs between individual playing cards when the top of the deck is moved relative to the bottom. 6. When rocks are subjected to stress, they tend to deform in one of two ways. They tend to either ___Break_____ or _____Bend____, depending on three main factors. Factors affecting deformation 7. There are three main factors that determine how a rock deforms when subjected to stress: Confining pressure/temperature, the __Strength___ of the rock, and __Time__. 8. In general, rock under high confining pressure (and higher temperatures) tend to __bend______ when subjected to stresses. 9. In general, stronger rocks like granite tend to ___Break______ when subjected to stresses. 10. Describe how time affects the deformation process-How the stress is applied over time will determine whether the rock bends or breaks

Types of deformation11. Rocks undergoing stress will initially experience ____Elastic_____ deformation, the only nonpermanent form of deformation. 12. Once the __Elastic______ __Limit_______ (strength) of a rock is exceeded, the rock will experience either __Ductile____ deformation (and bend) or ___Brittle_______ deformation (and break). 13. The feature resulting from either of the two permanent types of deformation is known as a geologic ___Time___. Mapping geologic structures14. In the field, geologists studying structures are interested in measuring two things: the __Strike__ of the layers or fault line and the ______Dip_____. 15. The __Fold__ (trend) is defined as the compass direction of the line produced by the intersection of an inclined rock layer or fault, with a horizontal plane. It is generally expressed as a compass direction or bearing (e.g., N10°E). 16. The __Dip__ (inclination) is defined as the angle of inclination of the surface of a rock unit or fault measured from a horizontal plane.

Types of structures17. When rocks deform plastically or ductilely, they are often bent into a series of wavelike undulations called ___Fold__. They most commonly result from compressional stresses which shorten and thicken the crust 18.In order to classify folds, you must first recognize and identify the parts of a fold. The _ Hinge__ is a line drawn down the points of maximum curvature of each layer. 19.The ___Axial_____ ____Plane_____ is an imaginary surface that cuts or divides a fold in half. 20.The two halves of the fold are referred to as _____limbs____. Common types of folds21.A linear, upwarped (or arched) fold in which the layers dip away from the center is referred to as a (an) _Anticline___. In this type of the structure, the ____Young___ (age) rocks are exposed in the center of the structure. 22.A linear down warped fold in which the layers dip towards the center is referred to as a (an) __Syncline_____. In this type of structure, the _Old____ rocks are exposed at the center of the structure 23.These basic types of folds may be _Symmetrical____ (if the limbs dip at the same angle), __Asymmetrical__ (if the limbs dip at different angles), or ____Over-turned____ (if the limbs dip in the same direction). 24.These basic types of folds may also be described as __ over-turned (if the axis of the fold is horizontal) or _______Recumbent__________ (if the axis is at an incline to the horizontal). 25.With a ____Inclined___ fold, the strikes are all straight and parallel to each other. 26.With a __Plunging ___ fold, the strikes wrap around forming a more or less U-shaped (or horse-shoe shaped) pattern. Other types of folds 27.A large, upwarped circular structure in which the oldest rocks are in the center is referred to as a __dome_______. 28.A large, down-warped circular structure in which the youngest rocks are found near the center is referred to as a ___Basins__. Faults29. Faults are __fractures________ (breaks) in rocks along which appreciable displacement has taken place. 30. Sudden movements along faults are the cause of most ___earthquakes___. 31. Just like with folds, there are parts of a fault that can be labelled. The body of rock directly above the fault plane is known as the ____hanging ___ ____wall____. The body of rock below the fault plane is referred to as the ___foot____ _____wall______. Geologists can also measure the strike and dip of the fault plane. 32. Faults are classified based on their relative __angle of dip____ along the fault plane. If the movement is primarily vertical (up or down the fault plane), the fault is referred to as a __Dip_____Slip____ fault. 33. If the hanging wall moves down relative to the footwall, the fault is referred to as a __ Normal___ fault. This type of fault most commonly results from _Compressional_____ stress associated with __divergent ___ plate boundaries. Large scale faulting of this type may produce mountains known as _Fault_- Block_ mountains. 34. If the hanging wall moves up relative to the footwall, the fault is known as a ____reverse____ fault. This type of fault most commonly occurs at __Convergent______ plate boundaries where the rock

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experiences __Tensional____ stress. If a fault of this type has a low angle of dip, it is called a __Thrust__ fault. Faults resulting from vertical movement along the fault plane may produce long low cliffs called fault ___scarps_________. Faults in which the movement is primarily horizontal is referred to as a ___Strike________Slip____ fault. There are two types of this kind of fault: ___Right_____- __Lateral____ and _____Left___- ___Lateral____ (which depends on which direction the rock on the opposite side of the fault moves relative to you as you face the fault). The San Andreas fault is a ___right___-__lateral___ strike-slip fault. If you have both horizontal and vertical movement along a fault, the fault is referred to as an _Oblique_-slip fault. _Fault-Scarps_ are fractures along which little or no movement has taken place. They most commonly occur in roughly parallel groups. They are important because of their influence on the ______Joints_________ of the rocks containing them....