ch15 flashcards
(26 cards)
fold
A bend or wrinkle in layered rock, formed when rock layers are deformed by compressional forces
anticline
An upward-arching fold in rock layers, with the oldest rocks at the core and rock layers dipping away from the center
syncline
A downward-arching fold in rock layers, with the youngest rocks at the center and rock layers dipping toward the fold’s core
asymmetrical fold
A fold in which one limb is steeper or more tightly compressed than the other, resulting in a non-mirrored shape
structural dome
A roughly circular or elliptical upward bulge in rock layers where the oldest rocks are in the center and layers dip outward in all directions
structural basin
A roughly circular or elliptical downward depression in rock layers, with the youngest rocks at the center and layers dipping inward from all sides
fault
A fracture or break in Earth’s crust along which movement has occurred, offsetting rock layers or structures
normal fault
A fault in which the hanging wall block moves down relative to the footwall block, typically formed by extensional (pull-apart) stress
reverse fault
A fault in which the hanging wall block moves up relative to the footwall block, generally due to compressional forces
thrust fault
A low-angle reverse fault where older rocks are pushed over younger rocks, often associated with large-scale mountain building
strike-slip fault
A fault in which rock layers slide past each other horizontally, with little or no vertical movement
left lateral fault
A type of strike-slip fault where the opposite side of the fault appears to move to the left when viewed from one side
right lateral fault
A type of strike-slip fault where the opposite side of the fault appears to move to the right when viewed from one side
headwall (hanging wall)
The block of rock that lies above an inclined fault plane
footwall
The block of rock that lies below an inclined fault plane
horst
An uplifted block of crust bounded by normal faults, standing higher than surrounding depressed blocks
graben
A down-dropped block of crust bounded by normal faults, forming a valley-like structure
scarp (fault scarp)
A steep slope or cliff formed directly by movement along a fault, marking the boundary between two differing elevations of land
triangular facets
Triangular-shaped landforms at the base of fault scarps where erosion has truncated ridges, commonly associated with active faulting
offset stream
A stream whose path is displaced laterally by movement along a strike-slip fault, creating a noticeable change in its course
shutter ridge
A ridge formed when a fault movement causes one side of a valley wall to shift, blocking or “shuttering” the valley or stream flow
sag ponds
Small ponds formed when ground movement along a fault creates a depression that fills with water, often found along strike-slip fault zones
hinge line (fold axis)
The line along the crest of a fold where the curvature is greatest, marking the boundary between limbs
linear valleys
Valleys formed by faulting or intense fracturing, often straight or linear due to the underlying structural control of a fault
