Volcanoes

Question 1

Igneous rocks form as _____ rocks _____ and ______

Answer 1

• molten
• cool
• solidify

Question 2

intrusive/plutonic rocks

Answer 2

rocks that crystallize at depth

Question 3

extrusive/volcanic rocks

Answer 3

magma that reaches the surface

Question 4

Magma consists of which 3 components?

Answer 4

• melts
• solids
• volatiles

Question 5

solids are generally _______ that have already _______ from the melt

Answer 5

• silicate minerals

- crystallized

Question 6

volatiles

Answer 6

gases dissolved in the melt

Question 7

rocks in the lower crust and upper mantle are near their _____ and any extra heat may induce ______

Answer 7

• melting points

- melting

Question 8

an ______ in confining pressure causes an ______ in a rock’s melting temperature

Answer 8

increase

Question 9

when confining pressures drop, _____ occurs

Answer 9

decompression melting

Question 10

most volcanoes are located within or near ______

Answer 10

ocean basins

Question 11

the main source of basaltic magma is

Answer 11

spreading centres slong mid-ocean ridges

Question 12

hot spots form ______ sources in oceanic crust and ______ sources in continental crust

Answer 12

• basaltic magma

- felsic magma

Question 13

magma at depth is ____ dense than the surrounding rock

Answer 13

less

Question 14

magma differentiation

Answer 14

• Separation of a melt from earlier formed crystals to form a different magma composition

Question 15

assimilation

Answer 15

Changing a magma’s composition by incorporation of foreign matter (country rock) into a magma

Question 16

fractional crystallization

Answer 16

progressive changes in the chemistry of slowly cooling magma because of sequential crystallization of different minerals

Question 17

batholith

Answer 17

• largest intrusive body

- frequently form the cores of mountains

Question 18

Largest known eruption

Answer 18

Yellowstone, 2500 km3

Question 19

shield volcanoes are _______ and composed primarily of _______

Answer 19

• broad and slightly dome-shaped

- basaltic lava

Question 20

shield volcanoes are produced by

Answer 20

mild, eddusive eruptions of large volumes of lava

Question 21

composite/stratovolcanoes are ______

Answer 21

large, classic-shaped volcanoes

Question 22

cinder cones are built from _______, are ______ in size, and frequently occur in ______

Answer 22

• ejected lava
• small
• groups or on flanks of other volcanoes

Question 23

domes are a _____ mass of ______, and can block openings leading to _______ of _______ magma

Answer 23

• bulbous
• congealed
• explosive eruptions
• gas-rich

Question 24

crater

Answer 24

steep-walled depression at the summit, generally <1 km diameter

Question 25

vent

Answer 25

opening connected to the magma chamber via a pipe

Question 26

caldera

Answer 26

- large depression at the summit of a volcano -formed when magma is withdrawn/erupted from a shallow underground magma reservoir

Question 27

as magma reaches Earth's surface, which 3 things occur?

Answer 27

- crystallisation - fractionation - exolution of volatiles

Question 28

Which factors control eruptive style by increasing explosivity?

Answer 28

- silica content - volatile content - high viscosity

Question 29

Subduction zones can be _____ and _____

Answer 29

- continental/oceanic | - oceanic/oceanic

Question 30

rift zones/spreading centres and hot spots can be _____ and _____

Answer 30

- oceanic | - continental

Question 31

Lava flows move _____ and reach temperatures of _____

Answer 31

- slowly | - 500 to 1,000 degrees C

Question 32

Aa basaltic lava has ____ viscosity, _____ texture, and forms _____ surfaces

Answer 32

- high - blocky - rough

Question 33

Pahoehoe basaltic lava has _____ viscosity, _____ texture, and forms ______ surfaces

Answer 33

- low - ropey - smooth, unbroken

Question 34

eruption columns can ______ and have potential _____ effects

Answer 34

- collapse | - climatic

Question 35

tephra fall is transported by _____, causes _____ collapse, ______ illness, and lead to ______

Answer 35

- wind and rain - building - respiratory - lahars

Question 36

ash impacts _____

Answer 36

airplanes

Question 37

pyroclastic flows have ____ velocity and temperatures of ______

Answer 37

- high | - 100 to 800 degrees C

Question 38

What is the most direct cause of death in eruptions?

Answer 38

pyroclastic flows

Question 39

lahars are hyperconcentrated __________, have _____ density, are highly _____, and can occur ________ an eruption

Answer 39

- volcanic mudflows - high - erosive - during or after

Question 40

Landslides are caused by

Answer 40

- magma intrusion - explosive eruption - gravitational collapse - earthquake

Question 41

tsunmis are responsible for _____ percent of volcano-related fatalities

Answer 41

25

Question 42

volcanic gases are directly responsible for ___ perfect and indirectly responsible for ___ percent of volcano-related fatalities

Answer 42

- 3 | - 40

Question 43

How do volcanic gases cause death?

Answer 43

- crop destruction - starvation - disease

Question 44

Volcano monitoring methods

Answer 44

- seismic - ground deormation - microgravity - geochemical - thermal

Question 45

We can prevent volcanic hazards by _____ lahars, _______ lava flows, and avoiding building in ______

Answer 45

- canalizing - water and solidifying - high-risk zones

Question 46

The Nevado del Ruiz eruption was _____ but had a ______ death toll

Answer 46

- small | - large

Question 47

the Mt. Pinatubo eruption was _____ but had a ______ death toll

Answer 47

- large | - smaller