!GLG 101-Illustrated Vocabulary-Chapter 17
!Tectonics-Folds and Faults
copyright 2003-Roger Weller
!angular unconformity
*a set of sedimentary layers deposited on an erosion suface which is underlain by
inclined sedimentary beds that are truncated by the erosion surface and then capped with
sedimentary layers parallel to the erosion surface.
!anticline
*a hill-shaped fold
!basin
*a tectonic structure in which layers of sedimentary rock formed into a circular
depression; the opposite of a dome
!basin and range faulting
*a series of fault block mountains (horsts) separated by basins formed by down dropped
blocks (grabens)
!basin and range province
*the southwest portion of the United States that is dominated by basin and range faulting
!basin and range topography
*the resulting land surface of mountains separated by valleys that is produced by basin
and range faulting
!brittle
*material has a tendency to break or crush; not tough
!compression
*a squeezing force that tends to flatten an object
!dip
*angle by which an inclined plane, such as a sedimentary bed or a fault surface, is tilted
from the horizontal
!dip-slip fault
*a type of fault in which the relative movement of the two fault blocks is in the dip
direction.
!drag fault
*a fold that is created when one sedimentary rock layer is dragged across another during
folding or faulting.
*[Santa Catalinas-Drag Fault]
!elastic
*after being distorted, the material snaps bach to its original, pre-stressed condition.
!fault
*a break in the planet's crust along which there has been movement.
*[California-Turbidites Cut by Fault]
!fault block
*the large mass of rock located on one side of a fault. Sometimes the term refers to a
single very large mass of rock surrounded on all sides by faults.
!fault gouge
*crushed and ground up rock along a fault
!fault zone
*is more complex than a single fault; it consists iof a series of faults all trending in the
same direction and tectonically related to eac
!fold
*bent layers of rock
*[Santa Catalinas-Folds-1]
*[Santa Catalinas-Folds-2]
*[Santa Catalinas-Folds-4]
!footwall fault block
*the fault block underlying a dipping fault surface
!geologic map
*a map that shows stratigraphic formations, folds, and faults
*[Map-Arizona-Patagonia Mountains]
!headwall fault block
*the fault block resting on top of an inclined fault surface
!joints
*flat breaks along which there has been little or no movement
*[Mt.Whitney-Plants Growing in Joints in Granite]
*[Mt.Whitney-Joints in Granite-1]
*[Mt.Whitney-Joints in Granite-2]
!normal fault
*a dip-slip fault where the headwall (upper) fault block slides down dip.
*[California-Turbidites-Normal Fault]
!open fold
*loose folds
!plastic flow
*under pressure, a material flows instead of breaking.
!plunging folds
*a series of folds whose fold axes are inclined to the horizontal.
!San Andreas fault
*a prominent strike-slip fault extending from near Yuma, Arizona, running northeast of
Los Angeles up through San Francisco. The San Andreas fault separates the Pacific plate
on the west from the North American plate to the east.
*[Map-California-Los Angeles]
*[Map-California-San Francisco]
!scarp
*a small cliff formed through mass wastage as a slump or landslide or through surface
faulting associated with an earthquake.
*[Landslide-Colorado-Scarp]
!shear
*the type of stress where one block slides past another block; materials caught between
the two blocks are said to be undergoing shear
!slickensides
*consist of parallel scratches on the rocks on both sides of a fault surface, formed when
the fault blocks rubbed against during fault movement.
*[Slickensides-1]
*[Slickensides-2]
!strain
*the consequeces of stress: folds, faults, joints, etc.
!stress
*the forces acting upon rocks: compression, tension, or shear
!strike
*In order to describe the oriention of a dipping surface, such as a fault or sedimentary
layer, this term is applied to the compass direction of the line created by the dipping
plane intersecting a horizontal surface
!strike-slip fault
*occurs when two fault blocks move horizontally past each other in opposite directions
along the direction of the strike line
!syncline
*a vally fold where the dips of the two limbs of the fold point towards each other.
*[FOLDS]
!tectonics
*the folds, faults, and earthquakes within a region that indicate the area is under stress or
has been under stress
!tension
*forces that pull structures apart
!thrust fault
*a low angle reverse fault; the headwall block moves up dip. TThis type of faulting is
caused by horizontal compression.
!tight folds
*a series of folds so tightly compressed that the limbs of the folds are nearly parallel to
one another.
*[Santa Catalinas-Tight Fold]
!topographic map
*a map that indicates elevation of landforms with contour lines.
*[Raised Topographic Map of the Mule Mountains]