14.2

Question 1

what are the two classifications for volcanoes?

Answer 1

shape
type of eruption

Question 2

lava plateaux/ fissure eruptions

Answer 2

shield volcanoes may erupt along lines of fissures rather than a central vent spilling liquid lava in successive layers

form broad plateaux such as the Colombia plateaux - often cut by deep canyons that expose the layers of rock - Grand Canyon

extensive lava flow are basaltic in nature so they can they can flow great distances

flat and featureless

macrofeature

Question 3

basic/shield volcano

Answer 3

3-4 miles wide and 1500-2000m tall

eg Mauna Loa

built up slowly by accreation of thousands of flows of highly fluid basaltic

low silica so spreads over wide areas

cools as thins forming gently dipping sheets

lava erupts form rift vents along fractures that develops on the flanks of the cone

magma has low gas content and is low in silica allowing it to flow over wide distances

Question 4

acid/ dome volcanoes

Answer 4

craggy, steep sloped convex sides covered with rock debris

typically found near large composite volcanoes

made of layers of lava

formed by repeated violent eruptions and slow moving lava flows which gives layered structure

magma is made of higher silica and high gas pressure making magma slow moving and explosive

eg Puy region of central france

Question 5

ash-cinder cones

Answer 5

formed from ash, cinders and volcanic bombs ejected from crater

sides are steep and symmetrical

eg Patricutun, Mexico

may occur as single volcanoes or secondary volcanoes on the sides of stratovolcanoes or shield volcanoes

tephra ejected

lava cools and builds up around the vent forming crater

build up over time

Question 6

composite volcano/ stratovolcano

Answer 6

tall and conical

built up from many layers of hardened lava, tephra, pumice and volcanic ash

steep profiles

periodically explosive and quiet eruptions

lava typically cools before spreading due to high viscocity

layered structure built up of sequential outpourings of eruptive materials

increase in temp causes dome to expand while its outer lava cools, causes newly hardened surface to splinter causing loose debris to fall from its sides

eg Mt Etna

Question 7

caldera

Answer 7

bowl shaped depression formed when volcano collapses into void left by empty magma chamber

Question 8

crater lake caldera

Answer 8

results from stratovolcano collapsing into its magma chamber during a violent eruption

Question 9

basalstic caldera

Answer 9

concentric ring pattern resulting from a series of gradual collapses
often found at summit of shield volcanoes such as the craters at the top of Mauna Loa

Question 10

resurgent calderas

Answer 10

largest volcanic structure
result from catastrophic eruptions that dwarf eruptions recorded by humans
Yellowstone Caldera

Question 11

lava type explosive volcano

Answer 11

rhyolite anderite

Question 12

lava type effusive volano

Answer 12

basalt

Question 13

lava characteristics explosive

Answer 13

acid high % silica
high viscocity
lower temp @ eruption

Question 14

lava characteristics effusive

Answer 14

low % silica
low viscocity
high temp @ eruption

Question 15

style of eruption explosive

Answer 15

violent bursting of bubbles when magma reaches surfacr

Question 16

style of eruption effusive

Answer 16

limited explosive force

Question 17

materials erupted explosive

Answer 17

ash, dust, lava bombs, tephra

Question 18

materials erupted effusive

Answer 18

gas, lava flows

Question 19

frequency of eruption explosive

Answer 19

long periods with no acitivity

Question 20

frequency of eruption effusive

Answer 20

more frequent

Question 21

shape of volcano explosive

Answer 21

steep sided strato volcanoes
caldera

Question 22

shape of volcano effusive

Answer 22

gently sloping sides
shield volcanoes
lava plataux

Question 23

strato volcanoes

Answer 23

made up of layers of ash and acid lava
concave symmetrical profiles
complex internal networks of lava flows which form minor igneous features such as sills and dykes

Question 24

caldera

Answer 24

volcanic craters
2km in diameter
eruption destroys cone and underlying magma chamber is emptied - sides collapse
eg Krakatoa

Question 25

archipelago

Answer 25

closely grouped cluster of islands Indonesia

Question 26

icelandic lava eruptions

Answer 26

large persistent fissure eruption large quantities of basaltic lava

Question 27

hawaiian eruption

Answer 27

runny basaltic lava travels down sides of volcano in lava flows gases escape

Question 28

strombolian eruption

Answer 28

frequent gas explosions large quantities of pyroclastic rock thrown out

Question 29

vulcanian eruption

Answer 29

blasts out of plugs fo sticky or cooled lava fragments build up into cones of ash and pumice viscous lava large quantities of ash

Question 30

vesuvian eruption

Answer 30

powerful blasts of gas pushing ash clouds high into the sky violent ash covers surrounding areas

Question 31

plinian eruption

Answer 31

gas rushed up through sticky lava ash and fragments clouds of gas and volcanic debris - kilometres thick

Question 32

lava plateaux

Answer 32

magma erupts from multiple fissures vast areas covered by free flowing lava - flood basalts millions of years of denudation create varied relief eg Columbia plateaux covers 130,000km2

Question 33

shield volcanoes

Answer 33

effusive eruptions found at divergent plate boundaries mostly occur at mid ocean ridges successive flows accumulate forming huge volcanoes eg Skjadbreidur, Iceland - example of above ground one

Question 34

eruptions at hot spot

Answer 34

fixed area of volcanic activity where magma from a rising mantle plume reaches the Earth's surface magma rises and forms island arc, and as plates move, island moves further away from hotspot and new island forms above hotspot creates chain of islands eg Hawaiian chain, pacific plate moves NW

Question 35

super volcanoes

Answer 35

volcano that erupts more than 1000km3 of material on a single eruption event exist as giant calderas eg Yellowstone last erupted 70,000 years ago

Question 36

what two factors need to be considered when assessing volcanic acitivity?

Answer 36

magnitude - amount of material erupted intensity- the speed at which material is erupted

Question 37

Volcanic Explosivity Index

Answer 37

combines magnitude and intensity into a single number on a scale 0-8 not good for effusive

Question 38

what factors are taken into consideration when assessing explosivity of the eruption?

Answer 38

volume of erupted material height ejected material reaches time duration

Question 39

lava flows

Answer 39

PRIMARY impacts dependent on type of lava basaltic lava is free flowing and can cover significant distances eg Hawaii 2015, covered 20km acidic lava is thicker and bulldozes everything in its path

Question 40

pycrolastic flows

Answer 40

PRIMARY combination of hot gases (500+ degrees), ash and rock fragments travelling at high speeds 100km/h follow contours of ground inhaling these gases causes instant death eg Pompeii

Question 41

tephra

Answer 41

any material ejected from a volcano into the air ranges in size from very fine- Pele's hair, Pele's tears to ballistic material - lava bombs, Lapilli buries farmland in layers of ash weight of accumulated ash causes buildings to collapse and people with respitory issues are at risk eg, eruption of Eyjafjallajokul 2010 caused cancellation of 100,000 flights

Question 42

toxic gases

Answer 42

PRIMARY eruptions emit CO2, carbon monoxide and sulfur dioxide deadly threat to human and livestock populations can causes acid rain also can cause limnic eruptions eg Lake Nyos killed over 1000 people

Question 43

lahars

Answer 43

SECONDARY mud flow with consistency of concrete snow and ice melt and mix with mud and flow rapidly down cone travel at 50km/h bury and destroy everything in their path eg Nevado de Ruiz, Columbia, 23,000 killed

Question 44

floods

Answer 44

SECONDARY eruptions beneath an ice field or glacier cause rapid melting vast quantities of water accumulate until they find an exit from under the ice aka jokulhlaup

Question 45

tsunami

Answer 45

violent eruptions of island volcanoes can cause massive displacement of ocean water and waves travleling at 600km/h eg Krakotoa, killed 36,000