Questions and Answers
What type of eruption is fed by silica-rich magma?
Which type of volcano is fed by mafic (basaltic) magma?
The upper lithosphere is associated with magma that has the greatest silica content.
True
What type of magma is found in the lower lithosphere?
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What is the definition of the asthenosphere?
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Which composition is associated with fast lava flow, flows in sheets, and comprises 90% of lava on Earth?
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What type of lava flow is characterized by silica-rich, slow-moving lava?
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_____ has a rough, broken surface. It is caused by rapidly moving basalt that cools quickly.
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_____ has a smooth, billowy surface. It is caused by slowly moving basalt that is still hot.
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_____ results from a relatively fluid lava cooling and forming an outer shell. The lava continues to flow inside the outer shell.
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_____ has a rough surface composed of smooth-sided fragments. It is formed by viscous lava cooling quickly.
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_____ is composed of solid, bubble-like masses. It is caused by extremely quick lava quenching.
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What type of volcanism characterizes the ring of fire?
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What type of boundary is present along the eastern boundary of the North American plate?
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At what tectonic setting is Hawaii located?
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What drives melting at divergent boundaries?
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Which tectonic setting does NOT produce volcanism?
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In order to cover such large expanses of seafloor, shield volcanoes erupt _____ lava.
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What interpretations can be made about the gas content of eruptions from cinder cone volcanoes compared to those of shield volcanoes?
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What information do geologists use to classify volcanoes?
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Cinder cones are made of _____.
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In general, how often do most cinder cones erupt?
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What are shield volcanoes generally made of?
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What is the range of shield volcano height?
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What are composite volcanoes made of?
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Why are shield volcanoes wider than composite volcanoes?
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What type of magma erupts out of dome complexes?
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What type of volcanoes are the highest?
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What is the range of dome complex height?
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Lavas erupting from composite cones are generally _____-rich, making them very viscous.
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Study Notes
Eruption Types
- Explosive eruption: Occurs with silica-rich magma, resulting in violent eruptions.
- Nonexplosive eruption: Involves mafic (basaltic) magma at high temperatures (around 1,000°C) and low dissolved gases, leading to less violent outflows.
Lithosphere and Magma Density
- Upper Lithosphere/Crust: Contains magma with equal or lesser density than the crust, rich in silica and experiences degassing.
- Lower Lithosphere: Composed of magma with density lower than the lower lithosphere but higher than the crust, undergoing partial crystallization of heavy minerals.
Magma Conditions
- Asthenosphere: Holds the hottest magma, crucial for volcanic activity.
Lava Composition and Flow
- Basaltic composition: Characterized by fast lava flow and accounts for 90% of Earth's lava, usually flowing in sheets.
- Andesitic composition: Represents intermediate lava flow.
- Rhyolitic composition: Features silica-rich, slow lava flow, making up only 1% of lava on Earth.
Lava Flow Types
- Aa flow: Rough, broken surface caused by rapidly cooling basalt.
- Pahoehoe flow: Smooth, billowy surface formed by slowly moving hot basalt.
- Lava tube: Formed when fluid lava cools and creates an outer shell while flowing inside.
- Block lava: Rough surface with smooth-sided fragments, resulting from quickly cooling viscous lava.
- Pillow lava: Composed of bubble-like mass formations caused by rapid lava quenching.
Volcanic Settings
- Ring of Fire: Characterized by convergent oceanic-continental and oceanic-oceanic boundaries, leading to significant volcanism.
- Eastern North American Plate: Features a divergent oceanic-oceanic boundary influencing geological activity.
- Hawaian Volcanoes: Located at an oceanic hot spot, showcasing unique volcanic characteristics.
Melting Mechanisms
- Divergent boundaries: Melting driven by decompression melting after the tectonic plates separate.
- Transform boundaries: Not associated with volcanism as they do not create magma.
Volcano Types and Eruptions
- Shield volcanoes: Erupt basaltic lava, capable of covering large areas; heights range from 300 to 10,000 meters.
- Cinder cones: Composed of pyroclastic deposits, generally erupt only once, and are characterized by more gas content in eruptions than shield volcanoes.
- Composite volcanoes: Also made of pyroclastic deposits, with eruptions involving more viscous, silica-rich lava.
Dome Complexes
- Erupt felsic magma and typically range in height from 500 to 2,000 meters, generally producing more viscous eruptions.
Volcano Classification
- Geologists classify volcanoes based on their shape and types of deposits produced, providing insight into eruption types and gas content.
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Description
Explore the fascinating world of volcanoes through this quiz that covers different types of eruptions, magma density, and lava compositions. Test your knowledge on explosive vs. nonexplosive eruptions and the conditions of magma in various layers of the lithosphere.
