Hazards Generated By Volcanic Acitivity

Question 1

Explosive erruptions

Answer 1

Convergent
Rhyolite & andesite
Violent, gas bubbles
Gas, dust, bombs, tephra, lava
Long periods with no activity
Steep sided - strato/composite

Question 2

Effusive erruptions

Answer 2

Divergent plate boundaries
Basalt lava
Gas bubbles expand freely
Gas and lava flows only
Frequent with eruptions over months
Gently sloping sides

Question 3

Icelandic lava erruptions

Answer 3

Persistent
Basaltic
Lava rises up through linear vent (fissure
Form large plateaus

Question 4

Hawaiian eruptions

Answer 4

Runny basaltic lava
Gases escape easily
Occasional pyroclastic flows

Question 5

Strombolian eruptions

Answer 5

Frequent gas explosions
Very explosive
White cloud/steam

Question 6

Vulcanian eruptions

Answer 6

Violent gases blast out plugs
Very viscous lava - solidifies quickly
Large quantities of volcanic ash

Question 7

Vesuvian eruptions

Answer 7

Very powerful blasts
Ash clouds high into sky
Lava flows also

Question 8

Plinian eruptions

Answer 8

Gas rushes up through lava
Immense thick ash clouds several km thick
Part of volcano blasted away

Question 9

Dyke

Answer 9

Igneous rock layer (magma) cutting across beds of rock

Question 10

Sill

Answer 10

Igneous rock layer (magma) running within rock beds

Question 11

Lava plateaus

Answer 11

Basaltic magma erupts from several fissures
Free flowing lava cools over time
Average 1 degree slope
I.e Iceland, Deccan plateau (india)

Question 12

Shield volcanoes

Answer 12

Divergent plate boundaries
Wide bases
Not very tall

Question 13

Hotspots

Answer 13

Plume of magma rises through the crust to create land (volcano)

As the plate moves, this creates and island chain

I.e Hawaii, moves 10cm/yr

Question 14

Super volcanoes

Answer 14

Any volcano that erupts more than 1000km^3 of material in a single eruption

Giant calderas

Extreme global impact

Question 15

Yellow stone super volcano

Answer 15

Began 2 million years ago

Last eruptions: 1.3 million years ago, 640,000 years ago, 70,000 years ago

75km caldera

Caused by a hotspot

Hydrothermal geyser eruptions

Question 16

Measuring/assessing volcanic eruptions

Answer 16

Magnitude - amount of material
Intensity - speed at which material is erupted

Volcanic explosively index (VEI)
0 - 8
Volume, height, duration
Logarithmic scale

Question 17

Lava flows

Answer 17

Basaltic - free flowing can run long distances i.e 20km Hawaii 2015

Rhyolite & andesite - Limited due to high viscosity

Will destroy everything in its path i.e crops, homes

Rarely causes injuries/fatlities

Question 18

Pyroclastic flows

Answer 18

Hot gases, ash and rock fragments travelling at speed

Follow the contours of the ground

Inhalation of poisonous gases = instant death

Question 19

Tephra

Answer 19

Any material ejected from volcano into air

Fine ash to volcanic bombs

Causes difficulty breathing and damage to infrastructure

Question 20

Toxic gases

Answer 20

Deadly/silent killer

Cause acid rain

Question 21

Lahars

Answer 21

Type of mudflow

Snow and ice on summit melt during eruption

Speeds of up to 50km/hr

Question 22

Floods

Answer 22

Beneath ice or glacier

Common in Iceland

Question 23

Tsunamis

Answer 23

Violent eruptions of island volcanoes

Krakatoa 1888 = 36,000 drowned

Question 24

Lake nyos, Cameroon

Answer 24

Deep lake which occupies a crater

2km wide, 200m deep

Gases can build up at bottom and eventually be released leading to poisoning and drowning