Test 1 stuff Flashcards
_____ are common and seismic hazard is high throughout the carribean
earthquakes
earthquakes cannot be reliably ___ or ___
predicted or mitigated
earthquake is composed of 3 forces
stress, strain, strneght
stress of an earthquake is
force per area
strain of an earthquake is
% distortion
strength of an earthquake is
rocks break at critical values
rocks deform ____, then rebound during an earthquake rupture
elastically
when the stress exceeds the strength of the rocks along the fault, it ___
slips
when the fault slips, it ____
releases the stress suddenly which causes an earthquake
____ ____ are ground vibrations caused by rocks slipping along opposite sides of a fault
seismic waves
why do earthquakes occur
elastic rebound theory,
fault rupture
where does the rupture of an earthquake begin
focus
machines that record seismic waves generated by earthquakes
seismographs
where are seismic waves generated
generated at earthquake focus
___ ___ travel over earth’s surface
surface waves
___ ___ and ___ ____ travel through earth’s interior
primary waves and secondary waves
seismic waves arrive in which order
primary, secondary, and surface
body waves travel where
through earth
surface waves travel where
along earth’s surface
2 types of surface waves
Rayleigh and love waves
2 types of body waves
P/S waves
have a push/ pull compressional motion (slinky)
travel through solids, liquids, and gases,
greatest velocity of all earthquake waves
4.8km/sec in continental crust
primary (P) waves
up-down motion
travels only through solids
slower velocity than P waves
3km/sec in continental crust
S waves
place within earth where earthquake waves originate
focus
point on the surface directly above the focus
epicenter
intersection of 3 circles from 3 recording stations is the
epicenter
each release in magnititude releases ___ times more energy
32
measure of the degree of earthquake shaking at a given locale based on the amount of damage
mercalli intensity
introduced by Charles Richter in 1935
measures the amplitude of sesmic waves
magnitude
measure very large earthquakes
derived from the amount of displacement that occurs along a fault zone and rupture area
moment magnitude (Mw)
causes pressure in pores between grains to increase and turns the substrate into a fluid
liquefaction of the ground
during liquefaction
saturated material turns fluid and underground objects may float to the surface
when is amplitude of shaking the ground greatest?
unconsolidated sediment and artificial fill
liquefactions sometimes causes
sand volcanoes or sand boils
harbor wave
tsunami
formed by something that rapidly moves large amounts of water
tusanmi
uplift of seawater during thrust faulting produces surge of water
tsunami
a tsunami is only a few ____ high in the deep ocean
cm
how fast do tsunamis travel
speed of a jetliner , so early warning systems are possible
tsunami sources from most frequent to less frequent
oceanic earthquakes, submarine landslides, volcanoes, meteor impact
estimates the probability that an earthquake of a certain magnitude will occur in a particular area during a specific time
earthquake forecasting
usable earthquake prediction has these factors
time interval in which quakes occur,
region where quakes occur
magnitude range of predicted quake
two forecasting strategies for earthquakes
find a specific precursor
forecast a general pattern
earthquake clustering theory
quakes are more likely when there are other quakes
seismic gap theory
quakes are due if they have not happened in a while
precursors to earthquakes
change in # of quakes, slow ground motion, radon’s emission, electrical resistivity, electromagnetic waves, water chemistry, seismic wave velocity, changes in animal behavior
estimate of the avg amount f time between large eq’s in a given location or on a given fault
recurrence interval
reduces eq’s generated forces acting on buildings
base isolation
more cohesive to less cohesive
damp sand, dry sand, water saturated snad
most common type of meteorite, 75-90% silicon, 10-25% Nickel-iron alloy
stony asteroid
likely from core of asteroid, mostly nickel-iron alloy
iron asteroid
shows which minerals are stable at depth
High P + T experiments
does earth’s magnetic field wander?
yes
has earth’s magnetic field reversed/
yes
dipole points ot south
normal polarity
dipole points to the north
reverse polarity
earth’s chemical layers
core(iron /nickl/sulfur) –> mantle (silicate material) –> crust (granite/ basaltic rocks)
earth’s physical layers
inner core (rigid) –> outer core (liquid) –> mesosphere (rigid) –> asthenosphere –> plastic –> lithosphere (rigid) –. ocean
seismic waves ____/____ at the interfaces between layers within the earth
reflect / refract
S waves DO NOT travel where
outer core
higher density in ____ vs mantle
outer core
describe S waves speed
increase in strong lithosphere
slight decrease in speed in weak asthenosphere
increase below asthenosphere in upper mantle
increase below the 410 KM mantle discontinutiy
increase below the upper / lower mantle transition.
geothermal gradient in normal continental crust is ___ to ____ per km
20 to 30 C
temperature near base of lithospehre
1400 C
outer core temperature
3000 C
inner core temperature
5000 C
in the p-wave shadow zone
no P or S waves recorded
in S wave shadow zone
only P waves recorded
p wave shadow zone is from
105 -142 due to reaction when they enter / leave the core
S wave shadow zone is from
105-180 because they cannot travel through outer core
sphere’s radius or inner core radius is
1216 kim
what makes up the inner core
iron nickel / iron nickel alloy
outer core radius
2270 km
what makes up outer core
iron and nickl
lower mantle is call dhte
mesophere
lower mantle is made up of
peridotite
part of upper mantle
asthenosperhe
velocity of seismic waves increases where
mohorovicic discontinuity
what separates crust from underlying mantle
mohorovicic discontinuity
is part of the crust / upper mantle
lithospehree
has a basaltic composition made up of Fe, Mg, SiO2 and is younger than the continental crust
oceanic crust
lower oceanic crust
gabbro
upper continental crust
basalt
continental crust is made up of elements
Na, K, SiO2
continental crust contains
granite
theory that outer rigid layer of the earth (lithosphere) is divided into plates that move acrosss the earth’s surface relative to each other
plate tectonics
who proposed the continental drift theory in 1912
weagner
evidence for continental drift theory
similar rock sequences in Appalachians / Great Britain/ other places
rock sequences contain rocks that form in tropical swamps. environments not found in current geographic locations
evidence of glacial activity where glaciers weren’t
fossils include fresh water creatures that could not swim across the ocean
evidence for pangea
wegnr noticed the folowing features matched on continents now separated by Atlantic Ocean
why was Wegner condemmned
bc he could not provide mechanism for movement
conviction in mantle could be ____ to drive movement of continents
mechanism
who proposed mantle convention theory in 1919
Arthur holmes
evidence for mantle conviction theory
seafloor bathymetry, seafloor ages, magnetic stripes on seafloor, younger seafloor = underwater mountains
subduction zones = ____ margins
destructive margins
mid-ocean ridges = _____
constructive margins
at transform boundaries
crust is not created or destroyed
transform boundaries
faults connect segments of a divergent boundary mountains = none (small) earthquakes are shallow no volcanoes san Andreas fault slide past each other
at divergent boudnaires
crust is created. youngest crust on planet at this boundary
divergent boundaires
yes for mountains eq's shallow yes to volcanoes example mid Atlantic ridge, East African rift, red sea separate
at convergent boundaries
Collin of two continental plates . crust is not created/ destoryed
convergent boundaires
mountains are the highest eq's are shallow-moderate no volcanoes Himalayas slam into each other
at convergent subduction boundary
crust is destroyed
what happens at convergent subduction boudnary
collision of two oceanic plates of collision of oceanic and continental
ocean-ocean boundaries form what
volcanoes on ocean floor/ volcanic island arcs
examples of ocean-ocean boundaries
Mariana / Tonga islands
convergen subduction
produces deep oceanic trenches forms mountains forms volcanoes eq's shallow- deep examples - andes mountains
originate deep within asthenosphere as molten rock which rises/ melts through the lithosphere plate forming a large volcanic mass at a hotspot
mantle plumes
where plates meet/ interact are ____
active margins
solid rock, located in crust / upper mantle, begins to melt
magma
to melt rocks at lower crust/ upper mantle we also need
additional heat
pressure
volatiles
partial meltin
equilibrium that exists between parts of the earth’s crust which behaves as if it consists of blocks floating on the underlying mantle. rises if material is removed. sinks if material is deposited
isostasy
volcanoes are formed from what
igneous rocks
cools and solidifies beneath earth’s surface (gabbros, diorite, granite)
intrusive igneous
cools and solidifies on earth’s surface (basalt, andesite, rhyolite)
extrusive igneous rocks
molten or partially molten rock beneath earth’s surface
magma
molten (solid) igneous rocks on earth’s surface
lava
factors that determine the violence of an eruption
composition of magma, temperature of magma, amount of gases in magma
measure of a material’s resistance to flow
viscosity
factors affecting viscosity
temperatues
composition
dissolved gases (volatiles)
higher temperature =
less viscous
higher silica content = ___ viscosity
lower silica content = ____ fluid
higher viscoity
more fluid
example of high silica
rhyolitic lava
example of low silica
basaltic lava
dissolved gases (volatiles) expand when they are near
the surface
least to greatest for composition / silica content / viscosity/ gas content / and ability to form prochalstic
basaltic (mafic) —> andesitic–> rhyolite (felsic)
long chains of silicon tetrahedra increase
magma viscosity
viscous magma produces more
violent eruptions
basaltic lavas are more
fluid
pahoehoe lava is
braids in ropes
Aa lava is
rough , jagged blocks
gases from magma / volcanoes
5% of magma by weight
mainly water vapor / carbon dioxide
pyroclastic materials are
fire fragmenets
pumice is from
frothy lavafr
lapilli is
walnut size
cinders are
pea-sized
conduit
pipe carrels gas-rich magma to surface
vent
surface opening
steep-walled depression at the summit
crater
summit-depression greater than 1 kim
caldera
broad, slightly domed
primarily made of basaltic (fluid) lava
generally large size
mayan loa in hawaii
shield volcanoes
built from ejected lava fragments
steeep slope angle
small size
occur in groups
cinder cones
most = adjacent to pacific ocean large size interbedded lavas and pyroclastic most violent Mt. Rainer , guatemala
stratovolcanoes (composite cone)
lahar
volcanic mudflow
nuee ardente
fiery cloud
resistant vents left standing after erosion removed volcanoes cone
ship rock, NM
volcanic necks
what controls eruption styel
magma composition
magma temp
gas content of magma
why is there a volcanoe in
italy
hawaiii
kenya
italy - plate tectonic convergence zone
hawaii = hot spot
kenya - continentla rift zone
ocean -ocean convergent plate boundary example
Aleutian Islands, Japanese archipelago
examples of hotspots
hawaii, yellowstone
general term that refers to all changes in the original form and/or size of a rock or body
deformation
most crustal deformation occurs where?
plate margins
deformation incise faulting or rigid rocks that can be ___
bent
brittle rocks are in
shallow crust
ductile rocks are in
deeper crust
permanet deformation , rock remains deformed
plastic
like a spring, release stress, and rock returns to original shape
elastic
strain accumulates to a point where the rock breaks (earthquakes
brittle
ductile rocks are what type of deformation
plastic
factors that influence the strength of a rocks
temperature and confining pressure
rock/mineral type
time
strain rate
3 types of stress
compressive
tensional
shear
squeeze and shorten a bodyq
compressive stress
stretch a body and tend to pull it apart
tenionsal stress
push two sides in opposite directions (twist or tears)
shearing
the 3 types of stress will determine what
what type of deformation will occur
determines whether a material behaves in a brittle of ductile fashion
strain rate
basic source of geologic information in the field
outcrop
represent the rock formation 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
orientation of a horizontal line within a plane
strike
angle of a layer of rock is tiled with respect to the horizontal
dip
rocks bent into a series of waves— most ___ result from compressional forces which shorten and thicken the crust (ductile, plastics)
folds
upfolded or arched, rock layers (A-shaped), oldest rocks in center
anticlines
downloaded rock layers (U-shaped), youngest rock - center
synclines
folds in rocks can be what
symmetricla
asymmetrical
overturned
limbs are mirror images. dip symmetrically from axis plane
symmetrical fold
limbs are not mirror images . one limb dips more steeply than the others
asymmetrical
one limb is tiled beyond the vertical
overturned
where folds die out
plunging
circular or slightly elongated
upward displacement of rocks
oldest rocks in core
oldest deformation exposed on surface
dome
circular or slightly elongated
down-warped displacement of rocks
youngest rocks in core
basin
movement along the inclination (dip) of fault plane
dip-slip faults
dominant displacement is horizontal and parallel to the trend or strike
strike-slip faults
rock above the fault surface
hanging wall
rock below the fault surface
footwall
hanging wall block moves down
associated with extension
prevalent at spreading center / rifts
caused by tensional foces
normal fault
hanging wall block moves up
caused by strong compressional forces
reverse fault is > 45 degrees
thrust fault is < 45 degrees
reverse/ thrust fault
older rocks on top of younger rocks
thrust fault has
example of normal fault
Wasatch fault in utah
example of thrust and reverse faults
Appalachian mountains ~ 1300 km of crustal shearing
large strike-slip fault that cuts through lithospehere
transform fault
no up-down motion of hanging walls - blocks slide past each other
transform faults
examples of a right-lateral transform faults
san Andreas fault
other deformation structures
cataclysmic textures, fault breccia , mylonite
brittle fractures along which no appreciable displacement has occured
joints
most ___ are formed when rocks in the outer - most crust has deformed
joints
extension of continental crust produces normal faults with high dip angles in the upper crust that flatten with depth, forming curved fault surfaces
tensional tectonics
compression of continental crust occurs on low-angled thrust faults
compressive tecctonics
shearing of continental crust occurs on a nearly vertical strike-slip fault
shearing tectontics
example of compressive tectnoics
Appalachians / himalays
example of shearing tectonics
san Andreas fault
examples of tensional tectonics
mid Atlantic rift
basin and range in west US
lake tanganyika
