Eosc 114 Midterm 2 Review

Front 1

Define volcano

Back 1

opening of the Earth’s surface where magma has poured or blown forth, typically creating hills or mountains

Form where magma/gas leak out of Earth’s crust/mantle

Front 2

Define magma

Back 2

molten rock material that solidifies on the Earth’s surface as volcanic rock and at depth as plutonic rock

Created by melting pre-existing rock below the Earth’s surface

Reach surface through fractures/extrudes as lava or explodes as pyroclastic material

Front 3

Define lava

Back 3

magma that flows to the Earth’s surface

Front 4

Describe the 4 stages of the volcanic system in chronological order. include where it is happening

Back 4

Source region: where the mantle is melting

- Where the mantle (peridotite) melts into magma of various types

- Becomes less dense

- Pockets of melting

Transport region: magma channels

- Where the magma is trying to get through the crust

- Magma moves along earth’s crust forming dikes and sills

Storage region

- Little bits of melt rising, cooling, and ponding in large chambersIn the crust

Eruption: Volcanoes on the surface

Front 5

Define dike

Back 5

vertical intrusion of magma

Front 6

Define sill

Back 6

horizontal intrusion of magma

Front 7

Give the approximate densities of magma, crust, mantle, and water

Back 7

Magma: 2.5-3.3 g/cm^2

water is 1 g/cm^3

Crust: 2.7-3.3 g/cm^3

Mantle: 3.3-5.7 g/cm^3

Front 8

Define viscosity

Back 8

resistance to flow

Front 9

What factors affect magma viscosity

Back 9

temperature, gas content, and crystal content

Front 10

How does viscosity affect eruptions

Back 10

Controls the flow and eruption style

Front 11

Describe the physical properties of felsic igneous rock. give one example

Back 11

high silica content (65-75%)

Light color

Rich in K, Na, Al, Si

High viscosity (sticky)

Eg. granite, rhyolite

Front 12

Describe the physical properties of mafic igneous rock. give an exampe

Back 12

Dark color

Rich in Mg, Fe

Low viscosity (runny)

Eg. Basalt, Gabbro

Front 13

Name characteristics of hot magma. which magma is hot

Back 13

low viscosity, low silica

Mafic

Front 14

Name the characteristics of cool magma. which magma is cool

Back 14

high viscosity, high silica

Felsic

Front 15

Which magma has more gas content? Name 2 gases that are dissolved in them

Back 15

felsic has more dissolved volatiles.

Gases dissolved: H2O, CO2, SO2, CI

Front 16

What type of eruption does mafic magma produce?

Back 16

low gas content+low viscosity=effusive eruptions (safe)

Front 17

What type of eruption does felsic magma produce?

Back 17

high gas content+high viscosity=explosive eruptions

the gas kept under pressure makes it dangerous explosion

Front 18

Name the characteristics of basalt rock. include Rock Description, Volume at Earth’s Surface, SiO content, Temperature of magma, Viscosity, Water dissolved in Magma, Gas escape from magma, Eruptive Style

Back 18

Black to dark grey, 80%, 45-55%, 1000-1300 C, Low, ~0.1-1wt, Easy, Peaceful

Front 19

Name the characteristics of andesite rock. include Rock Description, Volume at Earth’s Surface, SiO content, Temperature of magma, Viscosity, Water dissolved in Magma, Gas escape from magma, Eruptive Style

Back 19

Medium-dark grey, 10%, 55-65%, 800-1000 C, medium, ~2-3 wt%, More difficult, More explosive

Front 20

Name the characteristics of rhyolite rock. include Rock Description, Volume at Earth’s Surface, SiO content, Temperature of magma, Viscosity, Water dissolved in Magma, Gas escape from magma, Eruptive Style

Back 20

Light colored, 10%, 65-75%, 600-900 C, high, ~4-6wt%, difficult, explosive

Front 21

Define pahoehoe lava

Back 21

a basalt lava flow with a smooth, ropy surface

Front 22

Define Aa lava

Back 22

a basalt lava flow with a rough blocky surface

Front 23

What 2 main places do volcanoes occur on

Back 23

Plate boundaries, Hotspots

Front 24

What type of lava would one find at each type of plate boundary

Back 24

divergent- mafic, convegent-felsic

Front 25

What is an arc volcano

Back 25

chain of volcanoes formed above a subducting plate, positioned in an arc plate

Front 26

Descripe the eruptions at divergent boundaries

Back 26

Spreading centres allow peaceful eruption of magma

The most magma is erupted in this way

Front 27

Describe the eruptions at convergent boundaries

Back 27

Commonly explode violently

Magma temperature decrease, SiO2/water/viscosity increase

Front 28

Define hotspot

Back 28

places inside the mantle where rock melt to generate magma

Front 29

Where do hotspots occur?

Back 29

Fracture zones

Volcanic calderas (rhyolite rocks)

Under continental crust

- Ie Yellowstone

Under oceanic crust

- Ie. Hawaii

Front 30

what are the 4 main types of volcanoes

Back 30

Cinder cones: mafic, explosive

Shield volcanoes: mafic, non-explosive

Stratovolcanoes: intermediate, felsic, mixed

Calderas: felsic, explosive

Front 31

Define the angle of repose

Back 31

the steepest angle at which a sloping surgace formed of a particular loose material is stable

Front 32

What is the frequency of cinder cones

Back 32

frequent

Front 33

what is the frequency of shield volcaneos

Back 33

frequent/permanent

Front 34

What is the frequency of stratovolcanoes

Back 34

frequent

Front 35

What is the frequency of calderas

Back 35

rare

Front 36

Define effusive eruptions. what types of activity are associated with these types of lava flows and which types of magma do they occur for

Back 36

outpouring of molten magma from the vent → lavas

Passive eruptions of magma

- Lava flows (mafic-intermediate)

- Lava domes (felsic-intermediate)

- Gravitational collapse of lava flows/domes

- Pyroclastic flows

Front 37

Define explosive eruptions.

Back 37

gas driven violent eruptions → pyroclastic deposits

Buoyant eruption column of ash

Pyroclastic airfall

Pyroclastic flows (column collapse)

Blocks and bombs proximal to vent

Front 38

Define pyroclastic fall

Back 38

Eruption columns: 10’s of km

Widespread distribution of ash in the downwind direction

Ash blankets topography

Front 39

Define pyroclastic flow

Back 39

Gas-pyroclast mixtures

Gravity-driven flows

Flow down slope, channelled in valleys

velocity=40 to >400 km/h

temperatures=100-600 C

Front 40

What is the "key" to explosive volcanism

Back 40

high gas and high viscosity

Front 41

What are the steps to an eruption from the bottom of the volcano to the top?

Back 41

In the magma reservoir, there is magma with dissolved volatiles

Reaches the saturation surface

Exsolution surface → bubble nucleation

Bubble growth, bubble rise up the volcano within the magma

OutgassingFragmentation

Release as volcanic plume composed of pumice and ash

Front 42

Name the 5 types of eruption

Back 42

hawaiian, strombolian, vulcanian, plinian. phreatmagmatic

Front 43

Define the volcano explosivtiy index

Back 43

describes the size of an explosive volcanic eruption, scale 0-8

Front 44

What are the characteristics of a hawaiian eruption

Back 44

Low viscosity basaltic magma

Low explosivity (effusive)

- Lava flows

- Fire fountaining

Front 45

What are the characteristics of a strombolian eruption

Back 45

basaltic/andesitic magma

Mildly explosive

Bomb, lavas

Front 46

What are the characteristics of a vulcanian eruption

Back 46

Viscous andesitic/rhyolitic magma

Very explosive

Sustained explosions of ash

Front 47

What are the characteristics of plinian eruptions

Back 47

andesitic/rhyolitic ash

Violently explosive

Sustained column of ash

Pyroclastic flows

Front 48

What are the characteristics of phreatomagmatic eruptions

Back 48

Contact between water/magma

Water flashes to steam

Violently explosive

Surtseyan and phreatoplinian

Front 49

What characteristics are key in deciding the VEI of a volcano

Back 49

Volume of ash produced

Height of eruption cloud above vent

Duration of the eruption***

Total erupted volume explosively

Front 50

For every increase in interval on the VEI, what is the increase in size of eruption

Back 50

10 times larger

Front 51

What are the rough VEIs for hawaiian, vulcanian, plinian, and ultra plinian volcanoes

Back 51

Hawaiian: VEI 1

Vulcanian: 3

Plinian: 5

Ultra Plinian: 6

Front 52

True or false, some large eruptions can cause global cooling

Back 52

true

Front 53

true or false, as the VEI increase, the return period of another eruption of the same scale also increases

Back 53

true

Front 54

What is a hazard

Back 54

any event that could cause human or economic harm

Front 55

What is a risk

Back 55

the probability that a hazardous event may occur

Front 56

Name 5 volcanic hazards

Back 56

lava flows, pyroclastic ash fall, pyroclastic flows, lahars, sector collapse/debris avalanche, volcanic gases

Front 57

Define a lava flow

Back 57

Slow, Usually not dangerous, Easy to predict the flow path, Usually mafic and low viscosity

usually not a hazard to people but a hazard to buildings

Front 58

Define a fire fountain

Back 58

If basaltic lava is gas rich, small explosive eruptions from fire fountains

As particular liquid drops fall back on the ground, they may come together to form a lava flow

Front 59

Define a spindle bomb

Back 59

a football shpaed clot of magma that is chucked out of a volcano --> associated with low explosivity

Front 60

Define pyroclastic fall

Back 60

aka ash fall

hot ash and gas ejected from the volcano

can casue total darkness, roof collapse (most dangerous, and asphyxiation

Front 61

Define pyroclastic flows

Back 61

avalanche of pyroclastic material, air, and gas

driven by gravity

can travel 40-400km/h

Front 62

what are some triggers of pyroclastic flow

Back 62

collapse of a volcanic column (most common)

explosive collapse of lava domes

Front 63

what are some ways to reduce the threat from pyroclastic flow

Back 63

prevent construction/evacuate around the base of the volcano

aovid building where previous pyroclastic flows have occured

Front 64

Define a lahar

Back 64

volcanic mud/debris flow

flows of water and loose volcanic debris

prevalent at snow and ice clad volcanoes

can trave far and can occur without eruption

Front 65

define a sector collapse/debris avalanche

Back 65

a volcanic landslide

can occur when a volcanic edifice is weakened

scalloped scar remains

Front 66

Describe volcanic gases

Back 66

highly acidic and toxic

kills plants and animals

composed of water, carbon dioxide, HCl, SO2, and HF

Front 67

Define fumarole

Back 67

an opening in the volcano that may emit volcanic gases

Front 68

What are the 3 steps for volcano prediction

Back 68

1. geology and mapping

2. monitoring seismology and earthquakes, ground deformation, and gas emission, thermal imaging, lahar flow detction, and satellite observation

3. prediction and hazard analysis

Front 69

Describe the eruption warning levels

Back 69

GREEN (normal): volcano is in typical background, non-eruptive state or after a change from a higher level, volcanic activity has ceased and volcano has returned to non eruptive background state

YELLOW (advisory): volcano is exhibiting signs of elevated unrest above known background level OR after a change from a higher level, volcanic activity has decreased significantly but continues to be monitored for possible renewed increase

ORANGE (watch): volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain OR eruption is underway but poses limited hazards

RED (warning): hazardous eruption is underway, imminent, or suspected

Front 70

What does the interferometric synthetic aperture radar (InSAR) do?

Back 70

measurements by satellites to detect changes in elevation

Front 71

What does the tiltmeter do

Back 71

measures changes in angle of slope

Front 72

What does the GPS do in volcano monitoring

Back 72

measures changes in position

Front 73

What do spectrometers do

Back 73

measure carbon dioxide and sulfur oxide levels in gas from a distnace

Front 74

What are the 2 types of spectrometer and what are their differences

Back 74

FTIR (fourier transform infrared spectromter): used to measure dissolved volatiles in magma

COSPEC (correlation spectrometer): used to measure sulfur oxide in a volcanic plume

Front 75

How can you tell a rock if a rock is intrusive or extrusive

Back 75

the more crystal, the more intrusive it is

Front 76

At what type of convergence is there no volcano?

Back 76

continental continental

Front 77

What is the most common volcano at subduction zones

Back 77

stratovolcanoes

Front 78

What si the most common volcanoes at hotspots

Back 78

caldera and shield

Front 79

Where do cindercones appear

Back 79

anywher on the surface where there is basaltic magma and a little bit of gas leaks from it

Front 80

What is the difference between a flow and a slide

Back 80

a flow: everything is mixed up

a slide: everything is almost moving in a giant in tact-block

Front 81

what are some other terms for landslide

Back 81

mass movement, mass wasting, slide

Front 82

What are 3 factors that govern human and economic impact of landslides

Back 82

population density, cost of infrastructure, population preparedness

Front 83

what is the rough annual human impact of landslides in vancouver, us, and japan

Back 83

Canada-3, us-30, Japan-200

Front 84

True or false: most fatalities are associated with the landslide trigger and not the landslide itself

Back 84

true

Front 85

Why does BC get so many landslides?

Back 85

there are mountains everywhere

Front 86

What is the return period of large landslides in BC

Back 86

25-70 years

Front 87

Name 3 large landslides in BC

Back 87

In order of date: rubble creek (garibaldi), frank slide, britannia beach 1915, britannia beach 1923, hope slide, mt meager

Front 88

How are landslides classified?`

Back 88

type of material, type of movement, rate of movement

only material and type of movement used for name

Front 89

Name the 4 types of material a landslide can be composed of

Back 89

rock, soil/earth, mud, debris

Front 90

Name the 4 types of motion

Back 90

falls, slides, flows, complex movements

Front 91

What is the difference between a rotational and translational slide

Back 91

rotational: curved bowl shaped failure surface

translational: flat/planar failure surface

Front 92

What will the name of the motion be if the movement of a landslide is slow or slower

Back 92

creep, soil flow, or earht flow

Front 93

Where and why do falls occur

Back 93

falls are very fast and they occur on steep slopes where the material detaches because of weakness. the fall then occurs due to gravity

Front 94

Describe the characteristics of a rotational slide

Back 94

intermediate speed, usually weak material, rotation of material on a curved plane, often characterize by a curved scarp above the slide

Front 95

Describe the characteristics of a translational slide

Back 95

slow to fast, usually strong material moving on planes of weakness, cohesive motion on a flat surface

Front 96

describe the characteristics of flows

Back 96

very slow to very fast, soil mud or wet debris, water usually an important factor, fluid or plastic flow material

Front 97

Which forces are involved in the stability of slopes

Back 97

gravity and shear force (motion from side to side, component of force parallel to the slope), friction, cohesion (how the materials hold together)

Front 98

What is shear strength

Back 98

slopes ability to resist shearing motion

Front 99

When does failure occur?

Back 99

when shear strength is less than shear stress

Front 100

How do you calculate factor of safety (Fs)

Back 100

Fs=shear strength/shear stress

Fs less than one =failure

Front 101

What is the Factor of safety at the angle of repose?

Back 101

exactly 1

Front 102

What are some external causes of landslides?

Back 102

slope angle, undercutting overloading, vegetation (roots can bind loose material, removing them can make slopes unstable), climate: high temp and rainfall (weathered rocks, looser soil)

Front 103

What are some internal causes of slides?

Back 103

water content (can help or hinder cohesion but also weathers materials), weak material (eg. volcanic rock or quick clay), bad geological structures

Front 104

Define a trigger. list 5 for landslides

Back 104

A force or event that disrupts the equilibrium of a slope and intiates mass movement

eg. earthquakes, snow melt, heavy rainfall, rain or snow, loud noises, vehicles, eruptions, excavation, skiing, jumping up and down

Front 105

Describe the oso landslide

Back 105

march 22 2014, 45 days of heavy rain (cause), collapse of layers of glacial sediment (cause), trigger unknown but not earthquake, fast moving wall of mud, caused tsunami, 43 fatalities

Front 106

what are the 3 paths to mitigate landslides

Back 106

avoidance, prevention, protection

Front 107

what is the main problem with avoiding landslides

Back 107

too expensive