Chapter 12

Question 1

volcanic geosystem

Answer 1

the rocks, magma, and processes needed to describe the entire sequence of events from melting to eruption

Question 2

three types of lava

Answer 2

basaltic
andesitic
rhyolitic

Question 3

basaltic lavas

Answer 3

most common magma type
product of mantle melting
erupt when hot, fluid magmas fill up a volcano’s plumbing system and overflow

Question 4

pahoehoe

Answer 4

forms when a highly fluid lava spreads in sheets

Question 5

andesitic lava

Answer 5

lower temperatures than basalts

higher silica content - flow slower

Question 6

rhyolitic lava

Answer 6

lowest melting point

richest in silica

Question 7

tuffs

Answer 7

rocks created from smaller fragments such as ash

Question 8

breccias

Answer 8

rocks created from larger fragments

Question 9

types of central-vent volcanoes

Answer 9

shield
domes
cinder cones
stratovolcanoes
craters
calderas
diatremes

Question 10

shield volcano

example

Answer 10

occurs when basaltic lava flows create a shield-shaped volcano 2+ kilometers high and tens of kilometers in circumference
example - Mauna Loa

Question 11

volcanic dome

Answer 11

occurs when andesitic and rhyolitic flows (very viscous) are essentially squeezed out of the volcano with very little lateral spreading

Question 12

cinder cones

Answer 12

these are created when volcanic vents discharge pyroclasts that build up to create a cone
vent can become filled with volcanic debris that falls down the slope

Question 13

what is an angle of repose?

Answer 13

the maximum angle at which fragments in a cinder cone will remain stable rather than sliding down the slope

Question 14

stratovolcano

Answer 14

occur when alternating lava flow of lava and pyroclasts build a concave-shaped composite volcano

Question 15

crater

Answer 15

a bowl shaped pit found at the summit of most volcanoes

Question 16

calderas

Answer 16

when a lot of magma leaves the magma chamber, the chamber can’t support the roof so the roof collapses
can form a lake
yellowstone

Question 17

diatreme

Answer 17

when breccia fills the vent and channel below it after an explosion

Question 18

fissure eruptions

Answer 18

volcanic eruptions that come through vertical cracks in the Earth’s surface

Question 19

flood basalts

Answer 19

when successive flows of highly basaltic lava piles up

Question 20

ash-flow deposits

Answer 20

sheets of hard volcanic tuffs that come from pyroclast eruptinos

Question 21

at what type of plate boundaries are most volcanoes found?

Answer 21

convergent (80%)

Question 22

where do most fissure eruptions occur?

Answer 22

along mid-ocean ridges

Question 23

what forms when oceanic crust subducts below continental crust?

Answer 23

subduction zone volcanoes form volcanic mountain belts on land such as the Andes

Question 24

what forms when overriding lithosphere is oceanic?

Answer 24

subduction zone volcanoes form volcanic island arcs such as the Aleutian Islands

Question 25

intraplate volcanism

Answer 25

volcanoes far from plate boundaries

Question 26

hot spots

Answer 26

intense, localized volcanism far from a plate boundary

Question 27

how are hot spots formed?

Answer 27

hot, solid material rises through narrow jets from deep within the mantle

Question 28

mantle plumes

Answer 28

narrow jets of hot solid material that rise from deep within the mantle

Question 29

volcanic hazards

Answer 29

lahars
flank collapse
caldera collapse
eruption clouds

Question 30

what are lahars and how do they occur?

Answer 30

torrential flow of wet volcanic debris

occur when pyroclastic flows meet a river or snow bank or when a lava flow meets glacial ice

Question 31

flank collapse

Answer 31

the collapse of the side of a volcano
occur four times per century
if they occur underwater it can cause a tsunami

Question 32

eruption clouds

Answer 32

ash clouds than can damage airplanes

Question 33

how can eruptions be predicted

Answer 33

instruments monitor signals from earthquakes, swelling of the volcano, and gas emissions