ENVR Exam 2

Metamorphic Rocks

pre-existing rocks that have been subjected to increasing temperature and/or pressure

temperature and pressure

typically, __*blank*__ and __*blank*__ increase with depth

stresses

confining pressure and differential stress

confining pressure

rock experiences the same force on all sides

differential stress

rock does NOT experience the same forces on all sides

stress

can change the shape of the rock and shorten in the direction of maximum stress

as the rock shortens

the rock can develop planar features that are perpendicular to direction shortening

foliation

planar texture in metamorphic rocks

types of metamorphism

contact and regional

contact metamorphism

magma and/or hot fluids rising in the crust heat immediately surrounding rock

regional metamorphism

heat and pressure are applied to large area through burial or tectonic plates moving towards one another

parent

original rock

daughter

metamorphic rock resulting from heat and pressure

recrystallization

formation of cleavage and foliation is aided by the _____ of existing materials and the growth of new materials

remobilization

chemical constituents diffuse, dissolve, or partially melt in one place and then form crystals in another place

pressure solution

formation of cleavage -material dissolves from highly stressed edges of grains and precipitates elsewhere in the rock or is carried away by fluids

igneous rocks

Earth’s mantle is partially molten rock and is brought up to the crust where it cools into

what causes rock to melt?

change in temperature, change in pressure, change in composition or water content

how does molten rock cool

temperature gradually decreases within crust, temperature quickly decreases above the crust, specific minerals will crystalize at specific conditions

composition

tells us where the magma came from

texture

tells us how molten rock cooled

faster cooling rate results in

smaller crystals

slower cooling rate results in

larger crystals

extrusive volcanic igneous rocks

rocks cooled quickly at the surface

aphanitic

fine-grained

glassy

very fine-grained

vesicular

bubbly

intrustive (plutonic) igneous rocks

rocks cooled slowly below the surface

phaneritic

intrusive (plutonic) - coarse-grained

pegmatic

intrusive (plutonic) - very coarse-grained

porphyritic texture

two different cooling rates

igneous rocks are defined by

composition (felsic or mafic) and texture (rate of cooling)

granite

diorite

gabbro

periodotite

komatite

basalt

andesite

rhyolite

moho

the mantle can be best described as

semi-solid and mafic (roughly the same composition as olivine)

the outer core can best be described as

liquid; made mostly of iron

deepest mine on earth goes down to

crust

Evidence of Tectonic Plates

1. Continents “fit” together
2. Distribution of Fossils
3. Evidence of glaciers

paleomagnetism

convection in outer core and rotation of earth causes iron in core to move, creating a magnetic field

continental crust

enriched in Si, Al, and K

oceanic crust

enriched in Mg, Fe, and Ca

mantle

enriched in Mg and Fe

core

enriched in Fe and Ni

composition layers

coninental crust, oceanic crust, mantle, and core

mechanical layers

lithosphere, asthenosphere (upper mantle), mesosphere (lower mantle), outer core, inner core

lithosphere

brittle, cold, broken up into pieces

asthenosphere (upper mantle)

viscous, ductile

mesosphere (lower mantle)

solid, partially molten

outer core

liquid

inner core

solid

rocks from deep eruptions

can tell us interior layers are made out of

seismic waves from earthquakes can tell us about

the physical nature of Earth’s layers

seismic waves

travels faster through denser materials and through solids

a seismic wave

is a burst of energy traveling through Earth

refraction of seismic waves traveling in different media

causes the waves to curve

earthquakes generate

Primary and Secondary waves, which curve through the Earth

P-waves

are refracted inward at the liquid outer core because they slow down

Seismic waves are refracted

away from the Shadow Zone

S-Waves (secondary, shear, or side-to-side wave)

is slower than the P wave and arrives after it; they cannot travel through liquid

Seismic Tomography: red =

seismic waves; rising masses of hot mantle

Seismic Tomography; blue =

fast seismic waves; cooler, dense plates

lithosphere/asthenosphere

based on physical properties, brittle/ductile

Marie Tharp

developed the first map of the Atlantic sea floor in 1957

Tharp created the map using

sonar technology used to detected submarines in WWII and proposed the mid-Atlantic ridge as a rift

Bruce Heezen

initially dismissed the proposal until he discovered a cluster of seismic activity along the ridge

Harry Hess

developed the theory of Sea-Floor Spreading as the mechanism for Wegener’s Theory of Continental Drift

Norman L. Bowen

Began experimental studies to determine the order of crystallization of silicate minerals from magma

index minerals

series of minerals that form under unique metamorphic pressures and temperatures

volcano

naturally occurring rupture in the crust that allows lava, volcanic ash, and/or gases to escape

Mount Yasur

stratovolcano (composite volcano)

magma

molten rock within Earth’s crust

lava

molten rock above Earth’s crust

phenocrysts

larger crystals are called