5/19 Earthquakes And Volcanoes

Front 1

Combined effects of temperature and pressure are such that __to__ percent of mantle rock is molten.

Back 1

1 to 2 percent

Front 2

Three processes function to melt the asthenosphere to form magma:

Back 2

increasing temperature, decreasing pressure, and addition of water.

Front 3

_____-______ ______ produces magma beneath a spreading center, where hot asthenosphere rises to fill the gap left by the two separating tectonic plates.

Back 3

Pressure-release melting

Front 4

Pressure-release melting produces magma in a rising _______ _____ (small rising column of hot, plastic mantle rock). The magma rises to form a _________ _____ ______.

Back 4

mantle plume, volcanic hot spot

Front 5

Three processes melt the asthenosphere to form magma at a subduction zone:

Back 5

1) Steam rises from wet oceanic crust on top of the subducting plate;

(2) circulation in the asthenosphere decreases pressure on hot mantle rock;

(3) friction heats rocks in the subduction zone.

Front 6

________-_____ percent of the Earth’s active volcanoes lie in the “ring of fire,” a chain of subduction zones at convergent plate boundaries that encircles the Pacific Ocean.

Back 6

Seventy-five

Front 7

Magma forms abundantly in three tectonic environments:

Back 7

spreading centers (divergent plates)

mantle plumes

subduction zones

Front 8

In most cases, magma solidifies within the Earth’s crust to form a large mass of granite called a _______ .

Back 8

pluton

Front 9

A ________ is a pluton withmore than 100 square kilometers exposed at the Earth’s surface.

Back 9

batholith

Front 10

A ______ is similar to a batholith but has a smaller surface area.

Back 10

stock

Front 11

A _____ is a tabular, or sheetlike, intrusive rock thatforms when magma oozes into a fracture.

Back 11

dike

Front 12

When magma cools to form a sheetlike rock parallel to the layering of the crust we call this formation a _____.

Back 12

sill

Front 13

If lava is too viscous to spread out as a flood, it buildsa hill or mountain called a _______ .

Back 13

volcano

Front 14

Volcanic eruptions can be placed into two general categories:

Back 14

1) those that are explosive

2) those that are effusive

Front 15

In some cases, fissures extend for tens or hundreds of kilometers and pourthousands of cubic kilometers of lava onto the Earth’s surface. A fissureeruption of this type creates a _________ _______, which covers the landscape like aflood.

Back 15

flood basalt

Front 16

When many such fissure eruptions occur in rapid succession it creates a ______ _______ (basalt plateau) covering thousands of square kilometers.

Back 16

lava plateau

Front 17

Lava with low viscosity may continue to flowas it cools and stiffens, forming smooth,glassy-surfaced, wrinkled, or “ropy” ridges.This type of lava is called _______ .

Back 17

pahoehoe

Front 18

If the viscosity of lava is higher, the surface maypartially solidify as it flows. The solid crustbreaks up as the deeper molten lava continuesto move, forming ____ _____ with a jagged, rubbled,broken surface.

Back 18

aa lava

Front 19

If a volcano erupts explosively, it may eject both liquid magma and fragments called ______ .

Back 19

tephra

Front 20

The smallest particles, called ________ ______ , consist of tiny fragments of glass thatformed when liquid magma exploded into the air.

Back 20

volcanic ash

Front 21

Volcanic fragments thatvary in size from 2 to 64 mm are callled:

Back 21

Cinders

Front 22

Fragments greater than 64 mm are termed:

Back 22

volcanic blocks

Front 23

Clouds of gas and tephra that rise above a volcanoproduce an _______ _______ that can rise up to 45 km intothe atmosphere.

Back 23

eruption column

Front 24

Eventually the tephra in the eruptioncolumn will be picked up by the wind, carried for somedistance, and then fall back to the surface as . . .

Back 24

a tephra fall or ash fall.

Front 25

If the eruption column collapses a ______ _____ willoccur, wherein gas and tephra rush down the flanks of thevolcano at high speed.

Back 25

pyroclastic flow

Front 26

The deposits that are produced in a pyroclastic flow arecalled __________ if they contain pumice or _______ ______ _______ if they contain non-vesicular blocks.

Back 26

ignimbrites, pyroclastic flow deposits

Front 27

If the gas pressure inside the magma is directed outwardinstead of upward, a ______ _____ can occur.

Back 27

lateral blast

Front 28

When a lateral blast occurs on the flanks of a lava dome, a pyroclastic flowscalled a________ ______ can also result.

Back 28

glowing avalanche

Front 29

______ _______ often result from sudden exposure of the magma by alandslide or collapse of a lava dome.

Back 29

Directed blasts

Front 30

Lava and rock fragments commonlyerupt from an opening called a ______ located in a ______, a bowl-like depression at thesummit of the volcano

Back 30

vent , crater

Front 31

Fluid basaltic magma often builds agently sloping mountain called a _______ _______ .

Back 31

shield volcano

Front 32

A _____ ______ is a small volcanocomposed of pyroclastic fragments.

Back 32

cinder cone

Front 33

A cinder cone forms when largeamounts of what accumulates inrising magma?

Back 33

gas

Front 34

A ______ ______ consists ofalternating layers of lava andloose pyroclastic material.

Back 34

composite cone

Front 35

When granitic magma rises towithin a few kilometers of the Earth’ssurface, it_____ and ______ overlying rock.

Back 35

stretches and fractures

Front 36

In a volcanic eruption gas separates fromthe magma and rises to the upperpart of the _____ _____.

Back 36

magma body

Front 37

During a volcanic eruption, gas rich magma explodes through fractures, rising as a vertical column of _____ _____, _____ _____, and gas

Back 37

hot ash, rock fragments

Front 38

When exploding gas is used up during a volcanic eruption, thecolumn collapses and spreadsoutward as a _____-_____ ____ ____.

Back 38

high-speed ash flow.

Front 39

Because so much material haserupted from the top of the magmachamber during a volcanic eruption, the roof collapses to form a _______ .

Back 39

caldera

Front 40

Under stress, a rock may deform _______. And, in this particular case, if the stress is removed, the rock springs back to its original size and shape (releasing _____ ______ ______)

Back 40

elastically, the stored energy

Front 41

When its elastic limit is exceeded, a rock continues todeform like _____ . This behavior is called _____ .

Back 41

putty, plastic deformation

Front 42

True or False: A rock that hasdeformed plastically keeps its new shape when the stress is released, andconsequently does not release the energy used to deform it.

Back 42

True

Front 43

Every rock has a limit beyond which it cannot deform elastically. Undercertain conditions, an elastically deformed rock may suddenly fracture (creating a____).

Back 43

fault

Front 44

When large masses of rock in the Earth’s crust deform and thenfracture, the resultant rapid motion creates vibrations that travel through the Earthand are felt as an ________.

Back 44

earthquake

Front 45

An _______ is a sudden motion or trembling of the Earth caused by an abruptrelease of energy that is stored in the rocks.

Back 45

earthquake

Front 46

A ____ is a periodic disturbance in space and time, in which energy is transferred fromplace to place without the _______ of ______.

Back 46

wave, transfer of matter

Front 47

Waves, which move through matter, are called ______ _______ .

Back 47

mechanical waves

Front 48

Waves, which do notrequire a material medium, are called _________ ___________.

Back 48

electromagnetic waves

Front 49

Waves transmit energy from one point to another.Waves that travel through rock are called. . .

Back 49

seismic waves

Front 50

The initial point, where the abrupt movementcreates an earthquake, typically lie below thesurface at a point called the _____.

Back 50

focus

Front 51

The point onthe Earth’s surface directly above the focus is the_________.

Back 51

epicenter

Front 52

An earthquake produces several different types ofseismic waves. _____ waves travel through Earth’sinterior and carry some of the energy from thefocus to the surface. _____ waves then radiatefrom the epicenter along the Earth’s surface.

Back 52

Body, Surface

Front 53

Two main types of body waves travel through the Earth’s interior:

Back 53

P and S waves

Front 54

__ ______: compression elastic wave thatcauses alternate compression andexpansion of the rock.

Back 54

P wave

Front 55

P waves are calledprimary waves because they move ____ _____ that they are the firstseismic waves that reach an observer.

Back 55

move so fast (4-7 km per sec)

Front 56

___ : ____ waves are termed secondarywaves because they move more slowly (3-4km per sec) that __ waves.

Back 56

S wave, shear, P

Front 57

During an earthquake, ______ _______ move theEarth’s surface up and down and from side to side.

Back 57

surface waves

Front 58

A _________ records ground motion during an earthquake.

Back 58

seismograph

Front 59

The Earth’s major earthquake zones coincide with...

Back 59

tectonic plate boundaries