Week 5

Question 1

Volcanoes

Answer 1

• Normally found on plate boundary
• Very destructive

Question 2

Good Side of Volcanoes

Answer 2

• Volcanic rocks decompose very fast and are very rich agricultural soil
• The largest gold, copper, silver deposits are related to volcanoes
• Supply geothermal energy
• Recreation enjoyment

Question 3

The Ring of Fire

Answer 3

• Most volcanoes found here in pacific

Question 4

Magma

Answer 4

Molten rock inside of volcano

Question 5

Lava

Answer 5

Molten rock outside of volcano

Question 6

Pyroclastic material

Answer 6

Molten rock violently ejected from the volcano containing bombs, ash, and noxious gases

Question 7

Bombs

Answer 7

Blobs of molten rock thrown into the air

Question 8

Ash

Answer 8

Finely pulverized rock made up of fragments of the volcano walls, very light and can travel hundreds to thousands of km’s

Question 9

Basaltic

Answer 9

Low viscosity magma containing 45-55% silica, cooling to a black to dark-grey rock called Basalt.

Question 10

Andesitic

Answer 10

Intermediate viscosity magma containing 55-65% silica, cooling to a medium- to light-grey rock called Andesite.

Question 11

Rhyolitic

Answer 11

High viscosity magma containing 65-75% silica, cooling to a white, pink, or light-coloured rock called Rhyolite

Question 12

Rocks and Magmas: Silica

Answer 12

• The chemical compositions of many magmas are based on one mineral class, Silicates
• Made up up Silicon and Oxygen

Question 13

Volatiles

Answer 13

• Gasses dissolved in magma
• Water most common volatile
• High volatile means low viscosity, and violent eruptions

Question 14

Rocks and Magmas: Basalt

Answer 14

• 80% of the Earth’s igneous rocks are Basaltic;
• There are two textural types of Basaltic lavas:
• Aa(High viscous, rough)
• Pahoehoe (Low viscous, smooth)

Question 15

Rocks and Magmas: Andesite & Rhyolite

Answer 15

• Chemically-altered Basalts
• The main ”modification” is the SiO2 content – though water content does play a large role in determining eruptive style and rock type

Question 16

spreading centers

Answer 16

Magma that erupts at spreading centers is not melted; instead it’s described as a hot plastic that flows at just under its own melting temperature

Question 17

Subduction Zones

Answer 17

• Here, the water-saturated oceanic crust plays a huge role in the production of magmas that feed often violent terrestrial volcanoes
• Most dangerous and violent volcanoes

Question 17

Subduction Zones

Answer 17

Here, the water-saturated oceanic crust plays a huge role in the production of magmas that feed often violent terrestrial volcanoes

Question 18

Pyroclastic Flow

Answer 18

• Avalanche-like rush of hot gas and pyroclastic material that can cover hundreds of meters in just seconds;
• Pompeii deaths
• Nuée ardente is a pyroclastic flow that glows red due to heat

Question 19

Lahar

Answer 19

• Mudflows that contain pyroclastic material, water, trees, and anything else picked up on the way down the mountain

Question 20

Volcanic Degassing

Answer 20

Noxious and greenhouse emissions released by a volcano

Question 21

Lake Nyos, Cameroon (1986):

Answer 21

volcanic degassing occurred into Lake Nyos by underground volcanic vents, filling the summit lake with noxious gases; when a landslide triggered by an earthquake fell into the lake, it disturbed the gases that accumulated at the bottom, which spilled down the mountainside and onto the settlements below, choking the residents to death in their sleep; 1,700 people had died due to CO2 poisoning

Question 22

Volcanoes States

Answer 22

Active, Repose, Dormant, and Extinct.

Question 23

Short-Term Predictions

Answer 23

Precise and up-to-date, with danger zones identified; often use physical measurements of changes in the volcano to predict an eruption, based of its ”restlessness”

Question 24

ST: Seismic Disturbances

Answer 24

• Common for volcanoes to be covered with seismic monitoring stations to diagnose the magmas within
• Short-period/High-frequency earthquakes indicate fracturing within the magma chamber;
• Long-period/Low-frequency EQs indicate the magma has left the chamber and is heading up to erupt

Question 25

ST: Ground Deformation

Answer 25

As the magma builds up in the volcano reservoir, the ground will often bulge and deform; especially in the neck, where a magma dome can form

Question 26

ST: Degassing Evolution

Answer 26

The composition of the gases expelled by a volcano can be used to predict whether an eruption is likely

Question 27

Long-Term Predictions

Answer 27

General and observational, rooted in long-standing hazard assessment studies, rather than the current state of the volcano

Question 28

Hazard Assessment

Answer 28

• Studying the current and historical behaviours of a volcano are integral in hazard assessment
• Historical record is not always reliable, so we look to the Geological evidence left by volcanoes

Question 29

Other Indicators

Answer 29

Summit Lakes
Thermal Anomalies
Gravitational Tides