faults and folds

original horizontality

rocks are originally deposited in flat, horizontal positions (bc of gravity) with youngest layers on top

strike

line representing the intersection of a planar feature with a horizontal plane

dip

angle of a tilted bed relative to a horizontal plane

joint

fracture in earth’s crust, but with no displacement of rock bodies

hanging wall

block of rocks above the fault line 

footwall

block of rocks below fault line

compressional faults

reverse fault and thrust fault

reverse fault

hanging wall goes up, footwall goes down + fault angle GREATER than 45 degrees

thrust fault

hanging wall goes up, footwall goes down + fault angle LESS than 45 degrees

suture zone

a joining together along a major fault zone, of separate tectonic units often represented on the surface by a mountain range (the Himalayas)

tensional faults

normal fault and transverse fault

normal fault

hanging wall goes down, footwall goes up + produced by extensional forces

normal faults separate what?

horsts (a series of mountains) and grabens (valleys)

African rift valley

long, narrow band of downdropped rock (graben) caused by plates being pulled apart (tension)

transverse fault

strike-slip fault

strike-slip fault

blocks of rock slide past one another

horizontal displacement

left lateral: opposite side moves left

right lateral: opposite side moves right

folds

compressional force applied to rocks→ rather than breaking, they fold

anticline

arch-like folds with limbs dipping away from the axis (older rocks at center of fold)

syncline

trough-like folds with limbs dipping towards the axis (younger rocks at center of fold)

what type of fault is the san andreas fault?

right lateral transverse fault

an inclined fault (greater than 45 degrees) in which the hanging wall moves up relative to the footwall is a..

reverse fault

compressional stress is common in

suture zones

what is true regarding a syncline?

rocks dip towards the fold axis