Semester 2

Question 1

What is a volcano?

Answer 1

Surficial manifestation of a planet or moon’s internal thermal processes through emission of solid, liquid or gaseous products at discrete surface locations

Question 2

What was The Volcanic Age of Observation?

Answer 2

• William Hamilton
• 1750-1900
• James Hutten, the father of geology
• Neptunists vs Plutonists

Question 3

What were Neptunists?

Answer 3

• believe earth was static
• every rock was the result of precipitation from recreation ocean

Question 4

What were plutonists?

Answer 4

• earth in a constant state of flux (dynamic earth)

Question 5

How did volcano knowledge change in 1900s?

Answer 5

• pre 1970s volcanology more descriptive (not interpreted)
• Modern been more explanatory and investigative (volcano monitoring, hazard analysis, remote sensors)

Question 6

What is MAGATH? (factors control style of volcanic activity)

Answer 6

• Material (molten rock or ice)
• Available volatiles (gases)
• Gravity
• Atmospheric pressure
• Tectonic environment
• Heat generation mechanism

Question 7

What are the 2 main ways heat is generated?

Answer 7

• Radiation (decay of radioactive isotopes in interior liberates heat)
• Tidal forces (astronomical objects deform the interior, liberating heat)

Question 8

How is heat loss in a volcano?

Answer 8

Convection through plate tectonic snd mantle plumes

• conduction
• convection, mantle plumes
• convection, plate tectonics

Question 9

2 main types of volcanos

Answer 9

• Stratovolcano’s
• Shield volcanos

Question 10

What are stratovolcanoes?

Answer 10

built from layers of viscous lava flows and pyroclastic rocks from explosions

Question 11

What are shield volcanos?

Answer 11

layers of fluid lava flows, convex profile and can be enormous

Question 12

2 types of magma

Answer 12

• low viscosity magma
• high viscosity magma

Question 13

What is low viscosity magma

Answer 13

• magmas such as basalt
• produced at mid-ocean edges and hot spots
• create shield volcanos

Question 14

What is high viscosity magma?

Answer 14

• Andesite and rhyolite give rise to silicic volcanism
• produced at subduction zone settings
• create stratovolcanoes

Question 15

What is eruptive style determined by?

Answer 15

• Magma type
• Viscosity (more silica more viscosity)
• amount go gas present (gas causes explosivity)

Question 16

What are the levels of silica compared to viscosity?

Answer 16

low (50%) - Basalt
medium (50-65%) - Andesite
high (>65%) - Rhyolite

Question 17

What is magma a complex mixture of?

Answer 17

• Melt (molten rock)
• Crystals (solid rock)
• Gas

Question 18

What is andesitic and rhyolitic volcanism?

Answer 18

• gas can’t move freely
• pressure builds up leading to pyroclastic explosions
• eruptions lead to pyroclastic density currents (PDCs), causes column collapse

Question 19

What are 3 features of andesitic and rhyolitic volcanism?

Answer 19

Craters
Domes
Calderas

Question 20

What are components of the cryosphere?

Answer 20

seasonal snow
glaciers
ice sheets
sea ice
ground ice
river/lake ice

Question 21

2 facts about ice

Answer 21

lighter than water, 900kg m3
reflective (high albedo)

Question 22

What happens when snow survives summer melting?

Answer 22

Undergo transformation into ice

Question 23

Characteristics of glaciers?

Answer 23

ice thickness - 10 to 100s m
length - 1 to 10s km
velocity - 1 to 100m/yr

Question 23

Characteristics of glaciers?

Answer 23

ice thickness - 10 to 100s m
length - 1 to 10s km
velocity - 1 to 100m/yr

Question 24

2 ways of accumulation for glacier

Answer 24

Snowfall
Avalanches

Question 25

How does metamorphism of ice work?

Answer 25

Accompanied by densification (pores close of at 800)
- new snow (50-70)
- settled snow
- firn
- glacier ice (830-917)

Question 26

Ways of ablation

Answer 26

wind removal
melting + run-off
(iceberg calving)

Question 27

What is the equilibrium line altitude (ELA)?

Answer 27

located where annual mass balance is zero