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42 Cards in this Set

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states that when reconstructing earth history, one must assume the basic laws have always operated as they do today
principle of actualism
states that in a stack of layered rocks, the oldest is on the bottom
principle of superposition
states that layers of sedimentary rock are originally laid down in a nearly horizontal orientation
principle of original horizontality
states that rock layers were originally continuous over considerable lateral distance
principle of original lateral continuity
states that if any rock layer contains inclusions of another rock type, then the rock represented by the inclusions must have existed before the rock in which it is included
principle of inclusions
sstates that because life on earht has evolved over time, there is an understandable succession of fossils that can be used to help determine relative time
principle of biologic succession
defined as a buried surface of erosion or non-deposition , and they represent a period with no geologic record
unconformity
unconformity where the layers above and below the unconformity
disconformity
unconformity where the layers below are at an angle to those above
angular unconformity
unconformity where the rlationship between the beds above and below cannot be determined, usually where the underlying rocks are igneous or metamorphic
nonconformity
gaps in the time-rock records, surfaces that represent non deposition or erosion
unconformities
results from contact metamorphism
"baked" zone or aureole
physical character of a rock or rock formation.
lithology
study of layered sedimentary rocks
stratigraphy
basic subdivision of a geologic sequence
formation
plane along which adjacent formations touch is referred to as
contact
A horizontal layer of material, especially one of several parallel layers arranged one on top of another
strata
the angle at which beds descent into the earth, measure perpendicular tot he strike direction, angle measure from the horizontal plane to the bedding plane
dip
type of fold characterized by the rocks dipping toward the fold axis, and the youngest rocks in the fold are found nearest the axis
syncline
3 types of stress
tension, shear stress, compressional
layering of sedimentary rocks at a location os often drawn as a
geologic column
area where a rock unit is exposed at the earth's surface
outcrop
particularly recognizable beds like volcanic ash layers or thin black shales are called
marker beds
widely used method for correlating geologic units from one outcrop to another is by matching the
sequence of beds
when rocks change their shape or volume in response to specific pressures or forces they are
deformed
a bed , a layer of sedimentary rock that is distinguishable from the rocks above and below it, or layer that is no longer flat-lying(horizontal)
dip
describes how steeply the bed is dipping
dip angle
direction that a given bedding plane trends on teh surface of the earth
strike
a rock that has been bent is described as
folded
when the fold is arched up and the beds dip away from the center
anticline
when the fold is arched downward and the beds dip toward the center of the fold
syncline
where are the oldest rocks on a syncline
outside
when the fold is arched downward and the beds dip toward the center of the fold
syncline
a set of connected anticlines and synclines
foldbelt
deformation where all sides dip towards the center
basin
deformation where all sides dip away from the center
dome
bend subject to pressure
ductily
plane along which motion has occurred is called
fault plane
hanging wall moves up relative to the footwall due to compression or squeezing
reverse faults
low angle faults that result from compression, hanging wall moves up relative to the foot wall
thrust faults
faults that result from tension, hanging wall moves down relative to the foot wall
normal fualts
faults in which the motion along the fault plane is horizontal, rather than up or down
strike slip faults