5: volcanoes and volcanic hazards

Question 1

the two factors that determine the nature of a volcanic eruption

Answer 1

magmas viscosity and gas content

Question 2

volcanoes erupt

Answer 2

lava, gases, and solid pyroclastic material

Question 3

roughly viscosity basaltic lava can flow ____ distances

Answer 3

great

Question 4

when lava erupts underwater and the outer surface is instantly chilled while the inside continues to flow, it creates

Answer 4

pillow lavas

Question 5

gases most commonly emitted by volcanoes

Answer 5

water vapor and carbon dioxide

Question 6

gases that rapidly expanded upon reaching the earth’s surface that generate a mass of lava fragments

Answer 6

pyroclastic materials

Question 7

bubbles of gas in lava preserved as voids in rocks called

Answer 7

vesicles

Question 8

spots on volcanoes where only gas is expelled

Answer 8

fumaroles

Question 9

most shield volcanoes begin as

Answer 9

seamounts

Question 10

successive flows of low viscosity basaltic lava and lack of pyroclastic debris

Answer 10

shield volcano eruption

Question 11

consists of pyroclastic material and lava flows

Answer 11

composite volcano

Question 12

classic symmetrical cone shape

Answer 12

composite volcanoes

Question 13

erupts silica rich magmas of andesite or rhyolite

Answer 13

composite volcano

Question 14

volcano eruptions greatest threat to humans

Answer 14

pyroclastic flow

Question 15

a mix of hot gas and pyroclastic materials that race downhill at great speeds and incinerate anything and everything in it’s path

Answer 15

pyroclastic flow

Question 16

the welded deposit of pyroclastic materials

Answer 16

welded tuff

Question 17

steep sided structures composed mainly of pyroclastic debris and a basaltic composition

Answer 17

cinder cone volcano

Question 18

cinder cones easily succumb to

Answer 18

weathering and erosion

Question 19

volcano that forms from multiple erosions over millions of years

Answer 19

composite volcano

Question 20

mudflows that form on volcanoes that are rapidly moving ash and debris that suspend in water and follow stream valleys

Answer 20

lahars

Question 21

volcanoes that erupt at sea level can cause

Answer 21

tsunamis

Question 22

forms when the lava above a magma chamber can’t be supported and collapses causing a broad depression

Answer 22

caldera

Question 23

on what volcano does a caldera form slowly as lava drains from magma chambers beneath the volcano?

Answer 23

shield volcano

Question 24

on what volcano does a caldera collapse often follow an explosive eruption?

Answer 24

composite volcano

Question 25

volcanos form at both

Answer 25

convergent and divergent boundaries

Question 26

convergent boundaries that involve the subduction of oceanic crust are the most common site for

Answer 26

explosive volcanos

Question 27

what are large cracks in the crust called?

Answer 27

fissures

Question 28

thick masses of high viscosity silica rich lava that accumulates in the summit crater or caldera of a composite volcano

Answer 28

lava domes

Question 29

a column of mantle rock that is warmer and more buoyant than the surrounding mantle

Answer 29

mantle plume