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What component of magma is responsible for its liquid nature?
What component of magma is responsible for its liquid nature?
A dormant volcano is one that will never erupt again.
A dormant volcano is one that will never erupt again.
False
What is the primary gaseous component of magma responsible for explosive eruptions?
What is the primary gaseous component of magma responsible for explosive eruptions?
Water vapor
Magma is primarily found at depths of _____ to _____ km in the Earth's mantle.
Magma is primarily found at depths of _____ to _____ km in the Earth's mantle.
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Match the types of volcanoes with their definitions:
Match the types of volcanoes with their definitions:
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Which type of magma is rich in silica and characterized as felsic?
Which type of magma is rich in silica and characterized as felsic?
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Mafic lavas are associated with gentle volcanic eruptions.
Mafic lavas are associated with gentle volcanic eruptions.
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What are the three main factors that determine the eruptive behavior of a volcano?
What are the three main factors that determine the eruptive behavior of a volcano?
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The viscosity of rhyolitic magma is generally considered to be ______.
The viscosity of rhyolitic magma is generally considered to be ______.
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Match the types of magma with their corresponding silica content:
Match the types of magma with their corresponding silica content:
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What is the eruptive behavior of andesitic magma?
What is the eruptive behavior of andesitic magma?
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Dissolved gases in magma decrease the fluidity of the magma.
Dissolved gases in magma decrease the fluidity of the magma.
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Which type of magma typically results in violent eruptions?
Which type of magma typically results in violent eruptions?
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Which type of volcano is characterized by a broad base and gentle slopes, often resulting from the eruption of basaltic lava?
Which type of volcano is characterized by a broad base and gentle slopes, often resulting from the eruption of basaltic lava?
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Cinder cones are formed from the ejection of lava fragments that cool and harden during flight.
Cinder cones are formed from the ejection of lava fragments that cool and harden during flight.
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What is the most picturesque type of volcano that typically erupts explosively and has both lava and pyroclastic deposits?
What is the most picturesque type of volcano that typically erupts explosively and has both lava and pyroclastic deposits?
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The largest shield volcano on Earth is __________.
The largest shield volcano on Earth is __________.
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Match the following types of volcanoes with their characteristics:
Match the following types of volcanoes with their characteristics:
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Which of the following is NOT a characteristic of fissure eruptions?
Which of the following is NOT a characteristic of fissure eruptions?
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Lava domes are composed of low-viscosity lava that can flow easily over long distances.
Lava domes are composed of low-viscosity lava that can flow easily over long distances.
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What is the term for the structure formed from a narrow linear fracture through which lava erupts?
What is the term for the structure formed from a narrow linear fracture through which lava erupts?
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Which material is described as being ejected during a volcanic eruption in a semi-solid condition?
Which material is described as being ejected during a volcanic eruption in a semi-solid condition?
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Pumice is a heavy volcanic rock that sinks in water.
Pumice is a heavy volcanic rock that sinks in water.
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What is the general term used for airborne volcanic ejecta of any size?
What is the general term used for airborne volcanic ejecta of any size?
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____ is formed when gas-charged lava cools in flight and falls as dark volcanic rock.
____ is formed when gas-charged lava cools in flight and falls as dark volcanic rock.
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Match the pyroclastic materials with their descriptions:
Match the pyroclastic materials with their descriptions:
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Which pyroclastic material is characterized as having a size of 2-64 mm?
Which pyroclastic material is characterized as having a size of 2-64 mm?
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Lahars are a mixture of volcanic ash and snow.
Lahars are a mixture of volcanic ash and snow.
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What are the long-term effects of lahars on streams?
What are the long-term effects of lahars on streams?
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What type of lava flow is characterized by a smooth, undulating surface and is known as 'Pāhoehoe'?
What type of lava flow is characterized by a smooth, undulating surface and is known as 'Pāhoehoe'?
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Volcanic domes generally form from low-viscosity lava.
Volcanic domes generally form from low-viscosity lava.
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What is the term for fragments less than 2 mm in diameter produced during an explosive eruption?
What is the term for fragments less than 2 mm in diameter produced during an explosive eruption?
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The lava flow known as 'A‘ā' has a surface composed of ______ blocks.
The lava flow known as 'A‘ā' has a surface composed of ______ blocks.
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Match the following types of volcanic materials with their descriptions:
Match the following types of volcanic materials with their descriptions:
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Which of the following describes 'Pillow lava'?
Which of the following describes 'Pillow lava'?
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Hot spots are associated with higher concentrations of radioactive elements.
Hot spots are associated with higher concentrations of radioactive elements.
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In volcanic activity, what is formed when gas pressure in magma is released?
In volcanic activity, what is formed when gas pressure in magma is released?
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Study Notes
What is a Volcano?
- A volcano is a mountain formed when magma reaches the Earth's surface.
- Magma rises because it's less dense than the surrounding solid rock.
- Magma is molten rock found deep within the Earth.
- Magma collects in a magma chamber before being released as lava or pyroclastic ejecta through volcanic vents.
- Lava is molten rock that flows on the Earth's surface.
- Pyroclastic ejecta are fragments of rock and volcanic ash expelled during eruptions.
Magma Composition
- Magma is composed of a liquid melt, solid crystals, and a gaseous phase.
- The liquid melt consists of common Earth elements like silica, aluminum, potassium, calcium, sodium, iron, and magnesium.
- The solid component consists of crystallized silicate minerals.
- The gaseous phase includes water vapor, carbon dioxide, and sulfur dioxide.
Magma Sources
- Magma primarily originates in the upper mantle at depths of 50-250 kilometers.
- Temperatures are high enough, and pressure is low enough for rocks to partially or fully melt.
Volcano Activity
- Volcano activity is categorized as active, dormant, or extinct.
- Active volcanoes have erupted in recent history.
- Dormant volcanoes are inactive for the present but have the potential to erupt again.
- Extinct volcanoes are highly unlikely to erupt again.
Magma Composition and Eruptions
- Magma composition significantly influences the character of volcanic eruptions.
- Basaltic magma: Richer in iron and magnesium (mafic), produces less violent eruptions, and often forms shield volcanoes.
- Rhyolitic magma: Richer in silica (felsic), produces more violent eruptions, and often forms lava domes.
- Andesitic magma: Intermediate composition, produces eruptions of varying intensity, and often forms composite cones.
Factors Affecting Eruption Violence
- Magma composition: Viscosity (resistance to flow) is a crucial factor.
- Magma temperature: Hotter magma is less viscous and flows more easily.
- Dissolved gas content: Higher gas content increases pressure and can lead to more explosive eruptions.
Types of Volcanoes
- Shield volcanoes: Large, gently sloping volcanoes formed by the eruption of fluid basaltic lava.
- Cinder cones: Conical volcanoes built up from ejected lava fragments (cinders or scoria).
- Composite cones (stratovolcanoes): Large, steep-sided volcanoes formed by alternating layers of lava flows and pyroclastic deposits.
Volcanic Features
Fissure Eruptions
- Lava erupts from narrow fractures or cracks in the Earth's crust, often without explosive activity.
Lava Domes
- Mound-shaped accumulations of highly viscous lava, typically rhyolite or dacite.
- Can be unstable and prone to collapse, potentially generating pyroclastic flows.
Volcanic Pipes
- Vertical conduits through which magma rises.
Volcanic Necks
- Hardened magma within the pipe, exposed after surrounding rock erodes away.
Volcanic Materials
-
Lava flows: Molten rock that flows on the Earth's surface, categorized by their surface texture.
- Pāhoehoe flows: Smooth, billowy surfaces.
- 'A'ā flows: Rough, jagged blocks with sharp edges.
- Pillow lava: Rounded masses formed by underwater eruptions.
-
Pyroclastic materials: Fragments of rock ejected during explosive eruptions.
- Ash and dust: Fine volcanic particles.
- Welded tuff: Ash particles fused together by heat and pressure.
- Blocks: Large, angular fragments.
- Volcanic bombs: Lava chunks that solidify in flight.
- Lapilli: Small volcanic fragments (pea- to walnut-size).
- Scoria: Dark, vesicular volcanic rock (contains gas bubbles).
- Pumice: Light, frothy volcanic rock that floats.
- Tephra: General term for all sizes of volcanic ejecta.
Other Hazardous Volcanic Phenomena
- Lahars: Volcanic mudflows, a mixture of volcanic ash and water.
- Toxic gases: Volcanic gases can be poisonous, such as carbon monoxide, sulfur gas, and hydrochloric acid.
- Gas release: Large sudden releases of gas can be dangerous and unpredictable.
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Description
This quiz explores the fascinating world of volcanoes, focusing on the formation, composition, and sources of magma. Learn how magma rises to the surface, the elements that compose it, and its role in volcanic eruptions.
