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