Geology Final Exam Flashcards
A rock whose original minerology and/or texture has changed due to pressure and temperature WITHOUT melting
metamorphic rocks
protolith of blue schist
basalt
protolith of garnet-staurolite schist
shale
increase in temperature with increasing depth
geothermal gradient
average geothermal gradient
30C/km
minerals are stable over restricted conditions of T (and P)
geothermometry
pressure gradient
0.3-0.4 kbars/km
pressure in all directions (analogous pressure under water)
confining pressure
force exerted in a specific direction .causes folding, deformation, and minerals to align.
directed pressure
minerals are stable over restricted conditions of P (and T)
geobarometry
fluids can add or remove chemical components resulting in changes in the bulk composition
mesosomatism
protolith for gneiss
granite
protolith of marble
limestone
set of flat or wavy parallel planes produced by deformation
foliation
Foliated rocks are classified by
- crystal size
- nature of foliation
- segregation of minerals into light and dark bands
- metamorphic grade
order of increasing grade in metamorphic rocks (increasing metamorphic grade)
slate, phyllite, schist, gneiss, migmatite
heat from igneous rock intrusions metamorphoses surrounding rock (small scale)
contact metamorphism
heat and pressure are imposed over large areas of the crust (large scale).i.e. mountain belts. result from changes in P and T. rocks are deformed (folded and faulted). Formed from collision of tectonic plates.
regional metamorphism
metasomatism of the oceanic crust by hydrothermal circulation
hydrothermal (seafloor) metamorphism
meteorite impact
shock metamorphism
groupings of rocks of different mineral composition based on temperature and pressure. Minerals in a rock are clues to the history (P and T) of the rock.
metamorphic facies
the set of all P-T conditions experienced by a rock during its metamorphic history
Pressure-Temperature Path
increasing pressure and temperature
prograde
decreasing pressure and temperature
retrograde
pulls rocks apart,(stretching) at divergent boundaries.
rift valleys.
tensional forces
pushed rocks together (squeezing and shortening), at convergent boundaries.
mountain belts.
compressional forces
pushes either side of a formation in opposite directions, at transform boundaries.
i.e. san andreas fault
shearing forces
compressive features
folding, reverse/thrust faulting
tensional features
stretching, thinning, and normal faulting
shearing features
shearing, strike-slip faulting
minor internal strain, catastrophic break
brittle
smooth, continuous plastic deformation
ductile
folding, stretching, thinning, shearing
ductile
reverse, normal, strike-slip faulting
brittle
low confining P
low T
high strain rate
low water content
brittle
high confining P
high T
low strain rate
high water content
ductile
where do brittle deformations occur?
shallow crust
where do ductile deformations occur?
deep crust
the direction of the intersection of a rock layer with a horizontal surface
strike
angle at which the bed inclines from the horizontal (down and to the right of strike)
dip
fracture with no offset
joint
fracture with offset
fault
the wall that is below feet
footwall
FUN (Footwall Up Normal)
drops younger rocks down against older rocks (footwall older than hanging wall). divergent boundaries. found in rift zones.
normal faulting
FDR (Footwall Down Reverse)
puts older rocks on top of younger rocks (footwall younger than hanging wall). convergent boundaries.
reverse faulting
repeated sequences of large lateral displacement
thrust faulting
side to side movement, can still have footwalls or hanging walls
strike-slip faulting
a convex-upward fold whose core contains the older rocks (mountain shaped)
anticline
a concave-upward fold whose core contains the younger rocks (valley shaped)
syncline
an imaginary surface that divides a fold as symmetrically as possible
axial plane