Geology Exam 2

ion

an atom where Z (number of protons) does not equal the number of electrons

most polymerization minerals

crystallize at ~700 degrees Celsius

least polymerized minerals

crystallize first starting at ~1200 degrees Celsius

deformation of the ground surface

occur in hours or years, hard to detect

P-waves

primary waves, pressure or push-pull waves

Polymerization

linking of silica tetrahedra

deep focus

occur between ~300 &~670km depth

Augite (pyroxene)

(Ca,Mg,Fe)2Si2O6

olivine

(Mg,Fe)2SiO4

Hornblende (Amphibole)

(Na,Ca)2(Mg,Al,Fe)5Si8O22(OH)2

plagioclase feldspar

(Na,Ca)Al(Si,Al)Si2O8

lowest earthquake recorded

-2

fault formation

1. stress forms in earth's crust 2. crust deforms to accommodate stress 3. rock faults in response to excess stress

highest earthquake recorded

9.5

how much of the crust is oxygen

94%

how much of the crust is composed of silicate minerals

95%

anorthite (dark)

CaAl2Si2O8

biotite (dark)

K(Mg,Fe)3AlSi3O10(OH)2

muscovite (colorless)

KAl(AlSi3)O10(OH)2

potassium feldspar

KAlSi3O8

albite (light)

NaAlSi8O8

Quartz

SiO2, one of the most abundant minerals

element

a pure substance that cannot be separated into other components, defined by atomic number

convergent plate boundaries

all focuses of earthquakes, subduction zone, cascade mtn and japan

silica tetrahedron

basic unit of all silicates

biotite mineral

black, green-black or brown-black. Breaks easily along one plane forming thin, flexible sheets

ancient faults

can reactivate, do not need to form a new fault to get an earthquake

definite chemical composition

can write a formula, may be substitutions in the formula

naturally occurring

cannot be anthropogenic in origin

inorganic

cannot be produced by biological processes

muscovite mineral

colorless to silvery, and breaks easily along one plane forming thin, flexible sheets that may be transparent

hornblende mineral

dark gray to black with small-scale breaking at 56 degrees and 124 degrees. may appear splintery

augite mineral

dark green to brown or black. May form stubby crystals, Breaks at angles of 87 degrees and 93 degrees

foreshocks (cont)

development of smaller cracks eventually connect to form a major fault, do not always occur

independent tetrahedra

do not share any oxygens, bonded by cations, olivine

anomalous animal behavior

dogs barking, chickens not laying, rats on power lines, not scientific

short-term prediction

few hours to a week, relies of foreshocks

smallest earthquakes

few millimeters to centimeters

fault

fracture in rock along which sliding occurs; occurs above 15km depth

normal fault

hanging wall slips down the slope, result of tension(extension) in the crust

reverse fault

hanging wall slips up the slope, result of compression in crust

teeth

if not produced by living organisms, would be mineral apatite

New Madrid Fault

in early 1800s, four earthquakes with magnitudes over 7 in 2 months, 10,000 years old

places which straddle mid-ocean ridges

ireland, azores

collision (continent-continent)

large reverse and thrust faults, shallow and intermediate focus earthquakes, Himalayas

greater the slip

larger the earthquake

stages of earthquake cycle

long period of seismic inactivity, foreshocks, major earthquakes, aftershocks

love wave (l-wave)

make the ground surface tipple side-to-side like a snake

Rayleigh wave (r-wave)

make the ground surface to ripple up and down

homogenous solid

mineral is the same throughout, cannot be broken into simpler compounds, not a mineral if liquid or gas

seismic gaps

more time without earthquake, greater risk and magnitude of future earthquake

mineral

naturally occurring, homogenous solid, definite chemical composition, inorganic, ordered arrangement of the atoms (crystalline)

divergent plate boundaries composed of

normal faults which form at ridges axis transform faults which segment the axis

interplate earthquakes

occur at plate boundaries most common and intense occur at all types of plate boundaries form "seismic zone"

shallow-focus

occur at top ~15km of the Earth, most destructive

intermediate focus

occur between ~15km & ~300km depth

intraplate earthquakes

occur within plate may be intense but generally small result of movement along previously formed faults result of stress built in the plate

potassium feldspar mineral

orange to orange-pink color, and breaks at right angles

Bowen's Reaction Series

order in which minerals will crystallize from a magma

crystalline

orderly and regular repeating geometric pattern of atoms

composition of earth's crust

oxygen, sodium. magnesium, aluminum, silicon, potassium, calcium, iron

olivine mineral

pale or dark olive-green, with short crystals that appear granular (like sand). no distinct breaking surfaces

lower temperature

permits extensive polymerization

epicenter

point on the Earth's surface directly above the focus

high temperatures

reflect higher vibrational energy that prevents extensive polymerization

aftershock (cont)

result of rock slip as the crust responds to new stresses created by the major earthquake

major earthquake

result of slip along a major rupture surface

thrust fault

reverse fault in which the fault is less than 30 degrees from horizontal

at depths over ~670 km

rock is too hot and plastic for earthquakes

hanging wall

rock mass above the fault plane

footwall

rock mass below the fault plane

emission of radon

rocks expand and fracture, water seeps in and radon is pushed out

s-waves

secondary waves, shake or shear waves

body wave

seismic wave that pass through the interior of the Earth

surface waves

seismic waves that travel along the Earth's surface, most are destructive

divergent interplate earthquakes

shallow-focus earthquakes, continental rifts, mid-ocean ridges

earthquake prediction

short term prediction, deformation of the ground surface, seismic gaps, emission of radon gas, anomalous animal behavior

crystal

single, continuous piece of crystal material bounded by flat surfaces (=crystal faces)

strike-slip fault

slip is horizontal, result of shearing in the crust

large earthquakes

slip ranging from 0.5m to 13m

foreshocks

small to moderate earthquakes occurring hours or days before the next earthquake

aftershocks

smaller earthquakes that occur up to a year after the main earthquake

plagioclase feldspar mineral

sodium-rich samples are light in color, and calcium-rich samples are dark in color. Calcium-rich samples may exhibit a purple-blue iridescence. May exhibit fine-scale stripes or bands. Breaks at right angles.

Richter scale

specifies the amplitude of the largest ground motion at a seismograph 100km from the epicenter, logarithmic scale

focus (hypocenter)

spot in the crust where the fault begins to slip

transform plate boundaries

strike-slip faults, shallow-focus, San Andreas fault, Anatolian fault

double chain

tetrahedra share 2 or 3 oxygens, bonded by cations, hornblende

single chains

tetrahedra share 2 oxygens, bonded by cations, augite

sheet silicate

tetrahedra share 3 oxygens, bonded by cations, micas: muscovite and biotite

framework silicates

tetrahedra share all 4 oxygens, feldspars and quarts

intraplate earthquakes rock

transmit seismic waves efficiently, very damaging earthquakes

quartz mineral

usually colorless, white, or gray. May form hexagonal crystals. No distinct breaking surfaces and may appear massive

quartz composes grains of sand

very hard, does not dissolve easily, lack weak atomic bonds