Volcanoes and Eruptions

Question 1

Where do most volcanoes form?

Answer 1

Most volcanoes form over a hot spot or at plate boundaries above subduction zones

Subduction zones are areas where one tectonic plate moves under another, leading to volcanic activity.

Question 2

What is a subduction zone?

Answer 2

A subduction zone is where one plate dives beneath another plate

This process can lead to the formation of volcanoes and mountain ranges.

Question 3

At a subduction zone, what happens to metamorphic rocks?

Answer 3

Metamorphic rocks re-melt, making new magma that erupts through a volcano

This process is part of the rock cycle and contributes to volcanic activity.

Question 4

Volcan de Pacaya is classified as a:

Answer 4

Volcan de Pacaya is classified as a composite volcano

Composite volcanoes are characterized by a combination of explosive activity and lava flows.

Question 5

What type of volcano results from divergent plates moving apart?

Answer 5

Volcanoes that result from divergent plates moving apart are known as fissure volcanoes

These volcanoes often create new crust as magma rises to the surface.

Question 6

The three types of volcanoes with a steep slope are ash cinder-cone, composite, and:

Answer 6

The three types of volcanoes with a steep slope are ash cinder-cone, composite, and dome

Dome volcanoes are formed from the slow eruption of viscous lava.

Question 7

What is a caldera volcano?

Answer 7

A caldera volcano is formed from a violent eruption, where a big portion of the cone is destroyed leaving a depression

This depression can often fill with water, forming a lake.

Question 8

What are the largest volcanoes with quiet eruptions and a low slope called?

Answer 8

The largest volcanoes with quiet eruptions and a low slope are called shield volcanoes

Shield volcanoes are broad and have gentle slopes, formed by the flow of low-viscosity lava.

Question 9

What are solid particles, ashes, and hot gases spewed from composite volcanoes called?

Answer 9

They are called pyroclastic flows

Pyroclastic flows are extremely hazardous due to their high speed and temperature.

Question 10

When a pyroclastic flow combines with water, it forms a _______.

Answer 10

lahar

Question 11

What is a fissure volcano?

Answer 11

Long cracks in the Earth’s surface where lava erupts without a central cone

Example: Laki Fissure (Iceland), Krafla (Iceland)

Question 12

What type of lava is associated with fissure volcanoes?

Answer 12

Low-viscosity basaltic lava that spreads over large areas

Question 13

What is the eruption style of a fissure volcano?

Answer 13

Effusive eruptions, creating lava plateaus

Question 14

What is a shield volcano?

Answer 14

Broad, dome-shaped volcanoes with gentle slopes

Example: Mauna Loa (Hawaii), Galápagos Volcanoes

Question 15

What type of lava is found in shield volcanoes?

Answer 15

Low-viscosity, basaltic lava that flows easily and spreads widely

Question 16

What is the eruption style of a shield volcano?

Answer 16

Mostly effusive (lava flows rather than explosive eruptions)

Question 17

What is a lava dome?

Answer 17

A rounded, steep-sided mound formed by thick lava that piles up near the vent

Example: Mount St. Helens Lava Dome (USA), Novarupta (Alaska)

Question 18

What type of lava is associated with lava domes?

Answer 18

Highly viscous lava (rhyolitic or andesitic) that doesn’t flow far

Question 19

What is the eruption style of a lava dome?

Answer 19

Slow lava extrusion, but can have violent explosions if pressure builds up

Question 20

What is a cinder cone volcano?

Answer 20

Small, steep-sided cones built from volcanic debris (cinders, ash, and small lava fragments)

Example: Parícutin (Mexico), Sunset Crater (USA)

Question 21

What type of lava is associated with cinder cone volcanoes?

Answer 21

Basaltic to andesitic, often ejected explosively

Question 22

What is the eruption style of a cinder cone volcano?

Answer 22

Short-lived but explosive, creating loose cinder piles

Question 23

What is a composite volcano?

Answer 23

Large, steep-sided volcanoes made of alternating layers of lava, ash, and rock

Example: Mount Fuji (Japan), Mount St. Helens (USA), Mount Vesuvius (Italy)

Question 24

What type of lava is found in composite volcanoes?

Answer 24

High-viscosity lava (andesitic to dacitic), leading to explosive eruptions

Question 25

What is the eruption style of a composite volcano?

Answer 25

Explosive eruptions with ash clouds, pyroclastic flows, and lava

Question 26

What is a caldera?

Answer 26

A large crater formed when a volcano collapses after a massive eruption ## Footnote Example: Yellowstone Caldera (USA), Crater Lake (Oregon)

Question 27

What type of lava is associated with calderas?

Answer 27

Can vary, but often linked to supervolcanic eruptions with highly viscous magma

Question 28

What is the eruption style of a caldera?

Answer 28

Catastrophic eruptions, releasing enormous ash clouds and lava

Question 29

What is a Plinian Eruption?

Answer 29

Extremely violent eruptions with towering ash columns (over 30 km high) ## Footnote Produces large pyroclastic flows and widespread ashfall. Examples include Mount Vesuvius (79 AD) and Mount St. Helens (1980).

Question 30

What characterizes a Vulcanian Eruption?

Answer 30

Short, powerful explosions that eject ash, gas, and volcanic bombs ## Footnote More explosive than Strombolian but less sustained than Plinian. Examples include Sakurajima (Japan) and Anak Krakatau (Indonesia).

Question 31

Describe an Icelandic Eruption

Answer 31

Gentle eruptions from fissures, producing widespread lava flows ## Footnote Minimal explosion, mainly lava fountains and lava plateaus. Examples include Laki Fissure (Iceland) and Fagradalsfjall (Iceland).

Question 32

What is a Hawaiian Eruption?

Answer 32

Mild eruptions with fluid lava flows and lava fountains ## Footnote Low-viscosity lava spreads over large areas with little explosive activity. Examples include Kīlauea (Hawaii) and Mauna Loa (Hawaii).

Question 33

What characterizes a Strombolian Eruption?

Answer 33

Moderate explosions with bursts of lava ejected in arcs ## Footnote Occurs regularly and is less violent than Vulcanian eruptions. Examples include Stromboli (Italy) and Mount Erebus (Antarctica).

Question 34

What is a Pelean Eruption?

Answer 34

Highly destructive eruptions with pyroclastic flows ## Footnote Dome collapse or explosive blasts send hot ash and gases rushing down slopes. Examples include Mount Pelée (1902) and Soufrière Hills (Montserrat).

Question 35

What are pyroclastic flows?

Answer 35

Fast-moving, extremely hot (700°C+) clouds of ash, gas, and rock that race down volcano slopes. ## Footnote Pyroclastic flows are one of the most dangerous volcanic hazards due to their speed and temperature.

Question 36

What is the speed of pyroclastic flows?

Answer 36

Can travel over 100 km/h, destroying everything in their path. ## Footnote Their high speed and temperature make them particularly deadly.

Question 37

Name one historical example of a pyroclastic flow.

Answer 37

Mount Pelée (1902) or Mount Vesuvius (79 AD). ## Footnote Both events resulted in significant loss of life and property due to pyroclastic flows.