Terms Flashcards
force applied to a rock per unit area
stress
change in a rock’s composition by fluid transport of chemical substances into or out of it
metasomatism
the most widespread type of metamorphism that takes place where both high temperatures and high pressures are imposed over large parts of the crust
regional metamorphism
where the heat from an igneous intrusion metamorphoses the rock immediately surrounding it
contact metamorphism
where hot basaltic lava at a seafloor spreading center heats infiltrating seawater
seafloor metamorphism
low grade metamorphism that is caused by the progressive increase in pressure exerted by the growing layers of overlying sidemen’s and sedimentary rocks and by the increase in heat associated with increased depth of burial
burial metamorphism
rocks formed by pressure 8 to 12 kbar
high pressure metamorphism
rocks formed by pressures greater than 28 kbar
ultra-high pressure metamorphism
unusual metamorphic rocks once located at the base of the crust that are now found at the surface
eclogites
occurs when a meteorite collides with earth
shock metamorphism
a set of flat or wavy parallel cleavage planes produced by deformation of igneous and sedimentary rocks under directed pressure
foliation
rocks classified according to metamorphic grade, grain size, type of foliation, and banding
foliated rocks
the lowest grade of foliated rocks
slates
rocks of a slightly higher grade than slate
phyllite
the parallel arrangement of platy minerals that produces a coarse, wavy foliation known as schistosity; intermediate grade
schist
light colored rocks with coarse bands of light and dark minerals throughout the rock
gneiss
rocks that melt slightly before solidifying again creating a badly deformed and contorted rock that is penetrated by veins, small pods, and lenses of melted rock
migmatite
non foliated metamorphic rocks composed mainly of crystals that grow in equidimensional shapes such as cubes and spheres
granoblastic rocks
a high temperature contact metamorphic rock of uniform grain size that has undergone little or no deformation
hornfels
large crystals found in rocks formed both by contact and by regional metamorphism
porphyroblasts
the makeup of lowest grade rocks in regional metamorphism of a basalt
zeolite
a higher grade of metamorphosed mafic volcanic rocks
greenschists
mafic volcanic rocks where the pressure is high and the temperature is moderate
blueschist
groupings of rocks of various mineral compositions formed under particular conditions of temperature and pressure from different parent rocks
metamorphic facies
transported back to earth’s surface
exhumed
the distinctive history of changing temperature and pressure that is reflected in the texture and mineralogy of metamorphic rocks
P-T path (pressure-temperature path)
the remnant of such a boundary left behind in the geologic record
suture
stretch and pull rock formations apart and dominate at divergent boundaries
tensional forces
squeeze and shorten rock formations and dominate at convergent boundaries
compressive forces
shear two parts of a rock formation in opposite directions and dominate at transform boundaries
shearing forces
groups of rock layers that can be identified throughout a region by their physical properties
formations
the compass direction of a rock layer where it intersects with a horizontal surface
strike
the angle at which the rock layer inclines from the horizontal
dip
two dimensional representations of the rock formations exposed at earth’s surface
geologic maps
diagrams showing the features that would be visible if vertical slices were made through part of the crust
geologic cross sections
pliable
ductile
a fracture that displaces the rock on either side of it
fault
a fault on which there has been relative movement of blocks of rock up or down the dip of the fault plane
dip-slip fault
a fault on which the movement of blocks has been horizontal, parallel to the strike of the fault plane
strike-slip fault
the block of rock above a dipping fault plane
hanging wall
block of rock below a dipping fault plane
foot wall
a dip-slip fault if the hanging wall moves downward relative to the foot wall, extending the structure horizontally
normal fault
a low angled reverse fault so that the movement is more horizontal than vertical
thrust fault
faults that are both strike-slip and dip-slip
oblique slip faults
occur when an originally planar structure is bent into a curved structure
fold
folds in which layered rocks are bent upward into arches
anticlines
folds in which rocks are bent downward into troughs
synclines
have limbs that dip symmetrically from the axial plane
symmetrical folds
have one limb that dips more steeply than the other
asymmetrical folds
have limbs that dip in the same direction, but one limb has been tilted beyond the vertical
overturned folds
a bowl-shaped depression of rock layers in which the beds dip toward a central point
basin
a broad circular or oval upward bulge of rock layers
dome
a crack in a rock formation along which there has been no appreciable movement
joint
