Chapter 06: Volcanoes

Question 1

Volcanic activity causes (2)

Answer 1

Plate tectonics

Hot spots

Question 2

Violent eruption causes

Answer 2

High viscosity due to chemical composition (silicates; andesitic and granitic composition)

High gas content means gas under pressure, when pressure released, eruptions are more explosive

Question 3

Mild eruption causes

Answer 3

Low viscosity, basaltic composition

Low gas content

Question 4

Volcanic hazards (5)

Answer 4

High viscosity:
global hazards
climate conditions
air traffic

Low viscosity:
local hazards
lava flows

Question 5

Mount Tambora

Answer 5

Volcanic eruption in Indonesia, 1815

Caused the year without summer

Composite volcano (stratovolcano)

Question 6

Toba

Answer 6

Volcanic eruption occurred about 75kya

Caldera volcano

Global effects, killed off most humans, which affected the genetic makeup of current humans (population bottleneck)

Question 7

Gases of volcanic activity

Answer 7

Water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂)

Carbon dioxide: greenhouse gas, traps heat

Sulfur dioxide: Increases albedo of Earth’s atmosphere, deflecting heat from Earth

Question 8

Development of pyroclastic flows

Answer 8

Pyroclastic material erupts up, creating eruption column

Part of eruption column collapses (particles begin to settle) and flow downslope of the volcano

Question 9

Shield volcanoes

Answer 9

Mild eruptions

Basaltic composition, low gas content

Gradual sloping to volcanoes

Only hazard really is lava flows

Question 10

Composite volcanoes (stratovolcanoes)

Answer 10

Violent eruptions

Silica-rich magma/lava, high viscosity, granitic/andesitic composition

Steep slope of topographical profile

Question 11

Hot spot volcanoes

Answer 11

Topographical profile depends on composition of magma/lava

Formed by hot spot of mantle plume not associated with tectonic activity

Question 12

Caldera volcanoes

Answer 12

Volcanoes with depressions that formed from the evacuation of a magma chamber/resevoir and ground surface collapse

Type of sinkhole (not a crater)

Formed by subsidence and collapse rather than explosion or impact

Question 13

Mt. St. Helens

Answer 13

Violent eruption in 1980

Earthquake caused a landslide, leading to lateral eruption, then vertical (which lessened the regional impact by keeping debris localized)

Question 14

Plate tectonics & igneous activity

Answer 14

Igneous activity is not random

Most volcanoes are in or near oceans

Basaltic rocks - oceans & continents

Granitic rocks - continents

Question 15

Predicting volcanic activity (5)

Answer 15

Study history of eruptions

Topographic changes (e.g. swelling of volcano)

Seismic activity

Increased gases

Groundwater changes

Question 16

Yellowstone

Answer 16

2mya, 1.2mya, 600kya

Caldera volcano/supervolcano

Will most likely cause extinction

(Last time something like this happened = Toba)