2 a and b landforms, landscapes and hazards Created By Volcanic Eruptions

Question 1

Type of eruption at a convergent boundary

Answer 1

Explosive

Question 2

Explosive eruptions material ejected

Answer 2

Gases (direct and indirect greenhouse gases)
Ash
Pumice
Pyroclastic flow
Rhyolitic lava

Question 3

Explosive eruptions characteristics

Answer 3

Convergent boundary
Viscous rhyolitic lava
900°C
High silica content
Plinian eruption

Question 4

Effusive eruption plate boundary

Answer 4

Divergent

Question 5

Effusive eruption material ejected

Answer 5

Little gas
Basaltic (runny lava)

Question 6

Effusive eruption characteristics

Answer 6

Basaltic lava
Low silica content
1160°C lava
Icelandic and Hawaiian
Erupts over a long period of time
E.g. Erta Ale (EARV)

Question 7

Basaltic lava

Answer 7

48-52% silica (v low)
1160°C ( v hot)
Viscous lava

Question 8

Andenistic lava

Answer 8

52-63% silica
Somewhat viscous

Question 9

Rhyolitic lava

Answer 9

900°C (cool)
Viscous
68-77% silica

Question 10

3 ways magma is generated

Answer 10

1) increasing temperature causing rock to melt
2) decreasing pressure (decompression melting) as rocks ascend to lower pressure levels
3) introduction of volatiles ( principally water) lowers the melting point of rocks

Question 11

Hotspot definition

Answer 11

An area of intense volcanic activity where a mantle plume reaches the earth’s surface causing eruptions

Question 12

Are hotspots located on plate boundaries?

Answer 12

No

Question 13

What is the Hawaiian hotspot?

Answer 13

Pacific plate moves NW 10cm/year
Created basalt volcano peaks
As the plate moves volcanoes lose their source of magma and become extinct
Eroded and submerged

Question 14

Height of Muana Loa on Hawaii

Answer 14

400m above sea level

Question 15

Processes occurring at a hotspot

Answer 15

Localised source of heat energy that sustains a volcanism
The weight of the volcano bends the plate down
Isostatic change and later rebound
Thermal plume moves through dike

Question 16

East African Hotspot

Answer 16

Crust stretched under tension for 30 million years
Rifting has allowed magma to reach the surface creating a line of active volcanoes
Mount Kilimanjaro was formed this way

Question 17

Example of a hotspot volcano which is not shield

Answer 17

El Teide, Tenerife
Stratovolacano

Question 18

How much material is ejected by a supervolcano

Answer 18

1000km3 in a single eruption event

Question 19

Size of calderas

Answer 19

75km in diameter in Yellowstone
Huge

Question 20

Frequency of supervolcanic eruption

Answer 20

Infrequent
Last supervolcanic eruption was 27000 years ago in New Zealand

Question 21

Shot term impact of SV ash cloud

Answer 21

1000km3 material
Tephra falls into crops
Dust block stomata and cuticle, no photosynthesis, crop failure
Ashcloud prevents short wave solar radiation from entering the atmosphere, temperature drops
Famine and ecological deviation

Question 22

How many mass extinctions have been caused by volcanos

Answer 22

2

Question 23

Long term impacts of SV eruption

Answer 23

Direct GHG (CO2 H2O)
Indirect GHG (SO2 CO)
GHG effect
Global warming, sea level rise and extreme weather

Question 24

Magnitude of volcanic eruption definition

Answer 24

Amount of material erupted

Question 25

Intensity of volcanic eruption definition

Answer 25

Speed at which material is erupted

Question 26

The four factors measured for VEI

Answer 26

Magnitude
Intensity
Height ejected material
Duration of eruption

Question 27

Scale for VEI

Answer 27

0-8 (logarithmic)

Question 28

Evaluation of VEI

Answer 28

Less useful for effusive eruptions but is useful in determining relative impacts volcano might have on different geographic scales

Question 29

Jökulhlaups

Answer 29

glacial outburst flood
They occur when a lake (fed by glacial meltwater) breaches its dam and drains catastrophically
these floods are extremely powerful and high volume causing significant damage to surrounding land

Question 30

lava bomb

Answer 30

a mass of partially molten rock (tephra)
larger than 64 mm in diameter
formed when a volcano ejects viscous fragments of lava during an eruption.
Because volcanic bombs cool after they leave the volcano, they are extrusive igneous rocks.

Question 31

pyroclastic flow

Answer 31

hot gas , ash and rock fragments
up to 100kmph
highly destructive
localised effect
follow the topography
inhaling causes instant death
can cause pyroclastic dam from blocked river (delayed onset)

Question 32

lahar

Answer 32

mud flows combined with ash- warm
very destructive
follows topography
50kmph
can be formed due to melting glacier
monsoon can dislodge unconsolidated ash (delayed onset)