Questions and Answers
Where do most volcanoes occur on Earth's surface?
Most volcanoes occur along diverging plate boundaries or in subduction zones around the edges of oceans.
What process forms island arcs?
Island arcs are formed from subduction.
What causes hot spot volcanoes to form?
Magma from deep within the mantle melts through the crust.
What will eventually happen to the active volcano on the island of Hawaii, which is now over the hot spot?
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What are the stages that lead up to a volcanic eruption?
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Compare and contrast quiet and explosive volcanoes.
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Describe some of the hazards posed by volcanoes.
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What type of lava is formed from fast-moving lava that hardens into a rippled surface?
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Describe five landforms formed from lava and ash.
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Describe the process that creates a lava plateau.
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What features form as a result of magma hardening beneath Earth's surface?
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Describe how a dome mountain can form out of magma that hardened beneath Earth's surface.
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Study Notes
Volcanoes Location and Formation
- Most volcanoes occur along diverging plate boundaries and subduction zones near oceans.
- Island arcs are created through subduction, with magma rising through the crust to form underwater volcanoes.
Hot Spot Volcanism
- Hot spot volcanoes are formed when magma from deep within the mantle melts through the crust.
- The Hawaiian Islands are moving away from their hot spot as tectonic plates shift.
Volcanic Eruption Process
- Magma rises due to its lower density, leading to decreased pressure and gas bubble formation.
- Eruptions occur when pressure builds enough to create openings in weak rock, allowing gases and magma to escape.
Types of Volcanic Eruptions
- Quiet eruptions happen with easily flowing magma, producing pahoehoe and aa lava types.
- Explosive eruptions occur with thick, sticky magma, resulting in violent outbursts and hazardous volcanic gases.
Hazards Associated with Volcanoes
- Volcanic ash can damage infrastructure, disrupt air travel, and pose risks like roof collapses.
- Eruptions may trigger landslides and mudflows, exacerbating the hazards.
Characteristics of Lava Types
- Pahoehoe lava is characterized by fast movement and a smooth, rippled surface, typically produced by low-silica basalt magma.
Volcanic Landforms
- Various landforms result from lava and ash, including:
- Shield Volcanoes: Broad and gently sloping from repeated quiet eruptions.
- Composite Volcanoes: Alternating layers of lava and ash from both quiet and explosive eruptions.
- Cinder Cone Volcanoes: Cone-shaped hills formed from explosively ejected cinders.
- Calderas: Large depressions formed from the collapse of a volcano's magma chamber.
- Lava Plateaus: High, level areas created by multiple layers of lava flows.
Formation of Lava Plateaus
- Lava plateaus form through repeated flows from long cracks, building up over time as lava cools and solidifies.
Features from Hardened Magma
- Underground magma formations create features like volcanic necks, dikes, sills, batholiths, and dome mountains.
Dome Mountain Formation
- Dome mountains arise when rising magma bends overlying rock layers upward into a dome shape; erosion eventually exposes the dome.
Volcanic Landform Depletion
- A volcanic landform may form when a volcano depletes its magma chamber, resulting in enormous eruptions that alter the landscape.
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Description
Test your knowledge on the key concepts of volcanoes with these flashcards from Chapter 3. Learn about the locations of most volcanoes and the processes that create island arcs. Perfect for students seeking to reinforce their understanding of volcanic activity.
