angle of dip | A vertical angle measured downward from the horizontal plane to an inclined plane.
(See page(s) 359)
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anticline | An arched fold in which the rock layers usually dip away from the axis of the fold.
(See page(s) 361)
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axial plane | A plane containing all of the hinge lines of a fold.
(See page(s) 361)
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brittle | Cracking or rupturing of a body under stress.
(See page(s) 357)
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compressive stress | A stress due to a force pushing together on a body.
(See page(s) 357)
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dip-slip fault | A fault in which movement is parallel to the dip of the fault surface.
(See page(s) 367)
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direction of dip | The compass direction in which the angle of dip is measured.
(See page(s) 359)
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ductile | Capable of being molded and bent under stress.
(See page(s) 357)
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elastic limit | The maximum amount of stress that can be applied to a body before it deforms in a permanent way by bending or breaking.
(See page(s) 357)
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elastic limit | The maximum amount of stress that can be applied to a body before it deforms in a permanent way by bending or breaking.
(See page(s) 357)
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fault | A fracture in bedrock along which movement has taken place.
(See page(s) 358)
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fold | Bend in layered bedrock.
(See page(s) 361)
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footwall | The underlying surface of an inclined fault plane.
(See page(s) 361)
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geologic cross section | A representation of a portion of Earth in a vertical plane.
(See page(s) 360)
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geologic map | A map representing the geology of a given area.
(See page(s) 359)
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hanging wall | The overlying surface of an inclined fault plane.
(See page(s) 367)
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hinge line | Line about which a fold appears to be hinged. Line of maximum curvature of a folded surface.
(See page(s) 361)
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isoclinal fold | A fold in which the limbs are parallel to one another.
(See page(s) 364)
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joint | A fracture or crack in bedrock along which essentially no displacement has occurred.
(See page(s) 365)
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joint set | Joints oriented in one direction approximately parallel to one another.
(See page(s) 365)
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left-lateral fault | A strike-slip fault in which the block seen across the fault appears displaced to the left.
(See page(s) 372)
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limb | Portion of a fold shared by an anticline and a syncline.
(See page(s) 361)
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normal fault | A fault in which the hanging-wall block moved down relative to the footwall block.
(See page(s) 367)
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oblique-slip fault | A fault with both strike-slip and dip-slip components.
(See page(s) 367)
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open fold | A fold with gently dipping limbs.
(See page(s) 362)
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overturned fold | A fold in which both limbs dip in the same direction.
(See page(s) 364)
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plunging fold | A fold in which the hinge line (or axis) is not horizontal.
(See page(s) 362)
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recumbent fold | A fold overturned to such an extent that the limbs are essentially horizontal.
(See page(s) 364)
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reservoir rock | A rock that is sufficiently porous and permeable to store and transmit petroleum.
(See page(s) 371)
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reverse fault | A fault in which the hanging-wall block moved up relative to the footwall block.
(See page(s) 368)
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right-lateral fault | A strike-slip fault in which the block seen across the fault appears displaced to the right.
(See page(s) 372)
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shear stress | Stress due to forces that tend to cause movement or strain parallel to the direction of the forces.
(See page(s) 357)
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source rock | A rock containing organic matter that is converted to petroleum by burial and other postdepositional changes.
(See page(s) 370)
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strain | Change in size (volume) or shape of a body (or rock unit) in response to stress.
(See page(s) 356)
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stress | A force acting on a body, or rock unit, that tends to change the size or shape of that body, or rock unit. Force per unit area within a body.
(See page(s) 356)
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strike | The compass direction of a line formed by the intersection of an inclined plane (such as a bedding plane) with a horizontal plane.
(See page(s) 359)
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strike-slip fault | A fault in which movement is parallel to the strike of the fault surface.
(See page(s) 372)
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structural basin | A structure in which the beds dip toward a central point.
(See page(s) 362)
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structural dome | A structure in which beds dip away from a central point.
(See page(s) 362)
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structural geology | The branch of geology concerned with the internal structure of bedrock and the shapes, arrangement, and interrelationships of rock units.
(See page(s) 356)
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syncline | A fold in which the layered rock usually dips toward an axis.
(See page(s) 361)
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tensional stress | A stress due to a force pulling away on a body.
(See page(s) 357)
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thrust fault | A reverse fault in which the dip of the fault plane is at a low angle to horizontal.
(See page(s) 368)
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