chapter 18-19
most volcanoes form
at plate boundaries
T/F seismic waves change speed and direction when they encounter different materials
true
T/F seismologists have reasoned that earths outer core must be liquid based on the disappearance of s waves
true
T/F studies of how waves reflect deep inside earth show that earths inner core is solid
true
T/F the p wave shadow zone does not receive direct P waves
true
fault movement under the ocean plate can produce a
tsunami
wave generated by vertical motions of the seafloor
tsunami
basaltic magma forms when rocks in the ______melt
upper mantle
lava erupts through an opening in earths crust called a
vent
opening in earths crust through which lava erupts
vent
all of the following affect the temperature at which magma forms except
viscosity
internal resistance to flow
viscosity
this magma contains small amounts of silica and has a low _____
viscosity
tue modified mercalli scale ranges from
I to XII
most volcanoes occur
along convergent boundaries
largest pluton
batholith
types of plutons include
batholiths,stocks,sills,dikes, and laccoliths
depression that forms when the top or side of a volcano collapses into the magma chamber
caldera
which of the following forms when the top or side of a volcano collapses into the magma chamber
caldera
the most explosive volcanoes are
composite
rhyolitic magma forms deep beneath____crust
continental
a ______fault forms as a result os horizontal compression
reverse
in a______ the fracture is causes b horizontal shear and movement is mainly horizontal
reverse fault
______magma fuels volcanoes with intermediate eruptions
rhylotic
scale that measures energy released by a quake
richter scale
volcanism that occurs under water along mid ocean ridges is
rift volcanism
does not pass through earths liquid outer core
s wave
andestic magma forms from oceanic crust and
sediments
section of an active fault that has not experienced a significant earthquake for a long time
seismic gap
a paper or computer record of earthquake vibrations is called a
seismogram
A ______is an instrument that record earthquake vibration s
seismometer
pluton that is parallel tot the rocks it intrudes
sill
T/F Pwaves travel through earths mantle
true
T/F p waves are bent when they strike the core
true
pluton that cuts across preexisting rocks
dike
_____forms where two plates move apart
divergent volcanism
smallest of tephra sizes
dust
maximum earthquake intensity is usually found at the earthquakes
epicenter
magmas are named after _____rocks
extrusive
T/F S waves do not travel through earths mantle
false
T/F S wavs do not enter the core because they cannot travel through solids
false
T/F on seismograms, seismic waves recored from more distant facilities are closer together than those recorded from facilities close to the epicenter
false
T/F surface waves are the first to arrive at a seismic facility
false
fracture in rock along which movement occurs
fault
the surface along which fault movement takes place is the
fault plane
the moment magnitude scale takes into account the size of an earthquakes
fault rupture
one factor that determines the strength of an earthquake is the depth of its
focus
all seismometers include a _____ that is anchored to the ground and vibrates during an earthquake
frame
volcanoes that form far from plate boundaries are associated with
hot spots
the amount of damage done to structures by an earthquake is the earthquakes
intensity
the modified mercalli scale measures an earthquakes
intensity
as the distance from a quakes epicenter increases,
intensity decreases
mushroom shaped pluton
laccolith
when magma reaches earths surface it is called
lava
the amount of energy released by an earthquake is measured by its
magnitude
the richter scale is a numerical scale used to describe an earthquakes
magnitude
does not pass through earths interior at all
surface wave
seismic wave that causes the ground to move in two directions
surface wave
earthquake intensity depends primarily on the height of
surface waves
volcanic fragments thrown into air during a volcanic eruption
tephra
volcanic fragments thrown into the air during a volcanic eruption
tephra
irregulary shaped pluton that is similar to a batholith but smaller in size
stock
deformation of materials in response to stress
strain
forces per unit area acting on a material
stress
the san anders fault, a result of horizontal shear is a ____ fault
strike slip
a _____forms as a result os horizontal and vertical, resulting in a lengthening of the crust involved
strike slip fault
intrusive igneous rock body
pluton
bowl shaped depression around a vent at the top of a volcano
crater
bowl shaped depression that forms around the vent of a volcano
crater
all seismometers include a ____suspended from a wire or spring
mass
scale that rates earthquake intensity
modified mercalli scale
process responsible for the formation of many plutons
mountain building
along a ______, movement is both horizontal and vertical, resulting in a lengthening of the crust involved
normal fault
absence of this kind of waves results in a shadow zone
p wave
is refracted by earths core
p wave
squeezes and pulls rocks in same direction as the save travels
p wave
the time an earthquake occurred can be estimated from the
p wave arrival time
the focus of a catastrophic earthquake with high intensity values is almost always
shallow
broad gently sloping volcanoes with quiet eruptions are called
shield volcanoes