Volcanoes

Question 1

Which boundaries do volcanoes form on

Answer 1

Constructive and destructive
Aswell as hotspots in the Centre of some plates

Question 2

How do volcanoes form

Answer 2

-the upwelling of hot molten material from the core/mantle boundary
- OR from the top of a huge mantle plume just under the crust

Question 3

Fill in:
The shape of volcanoes is mainly related to the __ _ __ erupted

Answer 3

Type Of Lava

Question 4

what type of volcanoes are yellowstone and taupa

Answer 4

Super volcanoes

Question 5

what happens to volcanic hazards when magnitude increases

Answer 5

volcanic hazards increases

Question 6

TRUE OR FALSE are composite cones more dangerous than shield volcanoes

Answer 6

TRUE

Question 7

what factor causes the shape of volcanoes

Answer 7

the type of lava

Question 8

characteristics of composite volcanoes

Answer 8

composite volcano rises higher with a greater gradient than shield volcanoes
Produces a much greater ash cloud than shield
Has a quick eruptions
Has a longer period of time between eruptions
Narrow base
The magma is andesitic and likely melted from oceanic crust
Crate can be blocked causing violent eruptions

Question 9

what are the characteristics of shield volcanoes

Answer 9

Wide base
Gentle slope, less than 10 degrees
Magma rises directly from asthenosphere
Magma is basaltic
Gentle eruption - mainly lava occasionally ash from rare explosive eruptions

Question 10

define primary hazard

Answer 10

when a volcano erupts (immediate)

Question 11

what are the 4 primary hazard of volcanic eruptions

Answer 11

Lava flows
Emissions of gases and steam
Pyroclasts/tephra - ash, volcanic bombs
Pyroclastic flows

Question 12

define secondary hazard

Answer 12

a hazard that occurs after the eruption

Question 13

what are the 2 secondary hazards of volcanoes

Answer 13

jokulhaup
lahar

Question 14

what does the speed of flow of lava depend on

Answer 14

viscosity, temperature, silica content, and the volcanoes incline

Question 15

what lava is associated with composite volcanoes

Answer 15

andesitic lava

Question 16

what type of lava is associated with shield volcanoes

Answer 16

basaltic lava

Question 17

what type of lava is associated with super volcanoes

Answer 17

rhyolitic lava

Question 18

what is the hottest type of lava

Answer 18

basaltic lava

Question 19

what are the flow characteristics of andesitic lava

Answer 19

slow, intermediate viscosity, traps gases

Question 20

what are flow characteristics of basaltic lava

Answer 20

runny, low viscosity, thin, gases escape

Question 21

what are the flow characteristics of rhyolitic lava

Answer 21

thick, high viscosity, slow, gases are trapped

Question 22

the eruption energy of basaltic lava

Answer 22

gentle, effusive

Question 23

the eruption energy of andesitic lava

Answer 23

violent, moderately explosive

Question 24

the eruption energy of rhyolitic lava

Answer 24

very violent, cataclysmic

Question 25

is it true that gases can still be released even years after the volcanic eruption

Answer 25

TRUE Gases are released in and around volcanoes before, during and for many years after volcanic eruptions.

Question 26

what are the 2 main gases released by volcanoes

Answer 26

water vapour sulphur dioxide

Question 27

what can water vapour cause during eruptions

Answer 27

heavy rainfall or even lahars in some situations

Question 28

what can sulphur dioxide cause during eruptions

Answer 28

Forms fine particles that get carried as high as the stratosphere. These solid particles reflect radiation from the Sun back into space, so cooling the Earth.

Question 29

what are the gases released by volcanoes

Answer 29

water vapour sulphur dioxide fluorine gas carbon dioxide

Question 30

what can fluorine gas cause during eruptions

Answer 30

can be poisonous in high concentrations and can contaminate farmland or water supplies.

Question 31

what are pyroclasts

Answer 31

volcanic materials that are solid

Question 32

what are the 3 groups of pyroclasts

Answer 32

volcanic ash lapilli volcanic bombs/blocks

Question 33

how are the 3 groups of pyroclasts catagorised

Answer 33

via size of the pyroclasts

Question 34

what size is volcanic ash

Answer 34

less than 2mm

Question 35

what size is lapilli

Answer 35

2mm - 64mm

Question 36

what size are volcanic bombs/blocks

Answer 36

greater than 64mm

Question 37

how can ash cause hazards

Answer 37

its disruptive rather than devastating. Heavy ash can collapse roofs, damage crops and vegetation and affect people's breathing.

Question 38

what are pyroclastic flows

Answer 38

a dense mixture of superheated tephra and poisonous gases moving rapidly down the sides of a composite cone volcano

Question 39

how fast can pyroclastic flows travel

Answer 39

at speeds of up to 700 km/h

Question 40

an example of pyroclastic flows

Answer 40

for example, Chances Peak on Montserrat in 1997

Question 41

what can pyroclastic flows cause

Answer 41

leave behind thick layers of volcanic deposits (ignimbrite), up to 200 m thick may cause secondary hazards such as river flooding if they temporarily dam them example Pinatubo, Philippines 1991

Question 42

what are lahars

Answer 42

consist of water mixed with volcanic deposits flowing rapidly along existing valleys.

Question 43

how are lahars caused

Answer 43

heavy rainfall - a result of humid air being seeded with volcanic ash which accelerates condensation, the formation of clouds and rain emptying of a crater lake; or through the melting of snow and ice due to the heat from an eruption at high altitude

Question 44

what are the dangers of lahars

Answer 44

their fast velocity, the amount of material carried and the great distances they can travel.

Question 45

what is a jokulhlaup

Answer 45

A jokulhlaup is a flood of meltwater from underneath an ice cap or glacier.

Question 46

how does a jokulhlaup form

Answer 46

This happens when a volcano erupts underneath the ice and melts the ice so that it forms a lake, either in a crater or at the crater side where it is dammed by the ice. The warm meltwater will have sufficient volume to lift the ice away from the bedrock. When this happens the water bursts out underneath the ice carrying with it glacial moraines and blocks of ice.

Question 47

dangers of Jokulhlaup

Answer 47

The speed and volume of the event will wash away anything in its path and change the route of river channels.

Question 48

how do scientists measure eruptions

Answer 48

VEI (volcanic explosivity index)

Question 49

what factors does VEI use to measure a volcanoes eruption

Answer 49

Amount and height of volcanic material erupted How long the eruption lasts Qualitative descriptive terms (e.g gentle, explosive)

Question 50

what scale does VEI use

Answer 50

logarithmic 0 (non explosive) to 8 ( extremely explosive)

Question 51

how do scientists predict eruptions, what signs do they look for

Answer 51

Small earthquakes Changes to the volcanoes surface Changes to the volcanoes tilt

Question 52

a problem with predicting eruptions

Answer 52

they are never 100% accurate