Volcanoes and Eruptions Flashcards
Where do most volcanoes form?
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.
What is a subduction zone?
A subduction zone is where one plate dives beneath another plate
This process can lead to the formation of volcanoes and mountain ranges.
At a subduction zone, what happens to metamorphic rocks?
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.
Volcan de Pacaya is classified as a:
Volcan de Pacaya is classified as a composite volcano
Composite volcanoes are characterized by a combination of explosive activity and lava flows.
What type of volcano results from divergent plates moving apart?
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.
The three types of volcanoes with a steep slope are ash cinder-cone, composite, and:
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.
What is a caldera volcano?
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.
What are the largest volcanoes with quiet eruptions and a low slope called?
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.
What are solid particles, ashes, and hot gases spewed from composite volcanoes called?
They are called pyroclastic flows
Pyroclastic flows are extremely hazardous due to their high speed and temperature.
When a pyroclastic flow combines with water, it forms a _______.
lahar
What is a fissure volcano?
Long cracks in the Earth’s surface where lava erupts without a central cone
Example: Laki Fissure (Iceland), Krafla (Iceland)
What type of lava is associated with fissure volcanoes?
Low-viscosity basaltic lava that spreads over large areas
What is the eruption style of a fissure volcano?
Effusive eruptions, creating lava plateaus
What is a shield volcano?
Broad, dome-shaped volcanoes with gentle slopes
Example: Mauna Loa (Hawaii), Galápagos Volcanoes
What type of lava is found in shield volcanoes?
Low-viscosity, basaltic lava that flows easily and spreads widely
What is the eruption style of a shield volcano?
Mostly effusive (lava flows rather than explosive eruptions)
What is a lava dome?
A rounded, steep-sided mound formed by thick lava that piles up near the vent
Example: Mount St. Helens Lava Dome (USA), Novarupta (Alaska)
What type of lava is associated with lava domes?
Highly viscous lava (rhyolitic or andesitic) that doesn’t flow far
What is the eruption style of a lava dome?
Slow lava extrusion, but can have violent explosions if pressure builds up
What is a cinder cone volcano?
Small, steep-sided cones built from volcanic debris (cinders, ash, and small lava fragments)
Example: Parícutin (Mexico), Sunset Crater (USA)
What type of lava is associated with cinder cone volcanoes?
Basaltic to andesitic, often ejected explosively
What is the eruption style of a cinder cone volcano?
Short-lived but explosive, creating loose cinder piles
What is a composite volcano?
Large, steep-sided volcanoes made of alternating layers of lava, ash, and rock
Example: Mount Fuji (Japan), Mount St. Helens (USA), Mount Vesuvius (Italy)
What type of lava is found in composite volcanoes?
High-viscosity lava (andesitic to dacitic), leading to explosive eruptions
What is the eruption style of a composite volcano?
Explosive eruptions with ash clouds, pyroclastic flows, and lava
What is a caldera?
A large crater formed when a volcano collapses after a massive eruption
Example: Yellowstone Caldera (USA), Crater Lake (Oregon)
What type of lava is associated with calderas?
Can vary, but often linked to supervolcanic eruptions with highly viscous magma
What is the eruption style of a caldera?
Catastrophic eruptions, releasing enormous ash clouds and lava
What is a Plinian Eruption?
Extremely violent eruptions with towering ash columns (over 30 km high)
Produces large pyroclastic flows and widespread ashfall. Examples include Mount Vesuvius (79 AD) and Mount St. Helens (1980).
What characterizes a Vulcanian Eruption?
Short, powerful explosions that eject ash, gas, and volcanic bombs
More explosive than Strombolian but less sustained than Plinian. Examples include Sakurajima (Japan) and Anak Krakatau (Indonesia).
Describe an Icelandic Eruption
Gentle eruptions from fissures, producing widespread lava flows
Minimal explosion, mainly lava fountains and lava plateaus. Examples include Laki Fissure (Iceland) and Fagradalsfjall (Iceland).
What is a Hawaiian Eruption?
Mild eruptions with fluid lava flows and lava fountains
Low-viscosity lava spreads over large areas with little explosive activity. Examples include Kīlauea (Hawaii) and Mauna Loa (Hawaii).
What characterizes a Strombolian Eruption?
Moderate explosions with bursts of lava ejected in arcs
Occurs regularly and is less violent than Vulcanian eruptions. Examples include Stromboli (Italy) and Mount Erebus (Antarctica).
What is a Pelean Eruption?
Highly destructive eruptions with pyroclastic flows
Dome collapse or explosive blasts send hot ash and gases rushing down slopes. Examples include Mount Pelée (1902) and Soufrière Hills (Montserrat).
What are pyroclastic flows?
Fast-moving, extremely hot (700°C+) clouds of ash, gas, and rock that race down volcano slopes.
Pyroclastic flows are one of the most dangerous volcanic hazards due to their speed and temperature.
What is the speed of pyroclastic flows?
Can travel over 100 km/h, destroying everything in their path.
Their high speed and temperature make them particularly deadly.
Name one historical example of a pyroclastic flow.
Mount Pelée (1902) or Mount Vesuvius (79 AD).
Both events resulted in significant loss of life and property due to pyroclastic flows.
