Volcanic Hazards and Types
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Questions and Answers

Which elements primarily compose the common silicate minerals found in Earth's crust?

  • Aluminum and magnesium
  • Iron and nickel
  • Oxygen and silicon (correct)
  • Calcium and sodium

What is the main characteristic of granite regarding its mineral composition?

  • It is composed of only metallic minerals.
  • It contains various silicate minerals. (correct)
  • It is rich in iron and magnesium.
  • It contains only quartz.

What is the most common mineral group that consists of oxygen and silicon?

  • Silicates (correct)
  • Nitrates
  • Oxides
  • Carbonates

In relation to the viscosity of magma, which type of magma is typically associated with higher silica content?

<p>Rhyolitic magma (A)</p> Signup and view all the answers

What distinguishes volcanic (extrusive) igneous rocks from plutonic (intrusive) igneous rocks?

<p>Volcanic rocks cool rapidly at the surface, while plutonic rocks cool slowly below ground. (B)</p> Signup and view all the answers

What term is used to label igneous rocks that are silica-rich and dominated by light-colored minerals?

<p>Felsic (A)</p> Signup and view all the answers

Which of the following describes mafic igneous rocks?

<p>They are composed mainly of silica-poor minerals. (C)</p> Signup and view all the answers

In terms of crystallization, how do volcanic rocks typically compare to plutonic rocks?

<p>Volcanic rocks crystallize faster and have smaller crystals. (C)</p> Signup and view all the answers

What color are felsic igneous rocks primarily associated with?

<p>Light-colored (C)</p> Signup and view all the answers

What is the primary characteristic that distinguishes mafic rocks from felsic rocks?

<p>Mafic rocks are darker in color. (B)</p> Signup and view all the answers

How do geologists classify igneous rocks based on where they formed?

<p>By texture and composition. (A)</p> Signup and view all the answers

Which of the following is a correct classification of an intermediate igneous rock?

<p>Andesite (D)</p> Signup and view all the answers

What is the relationship between the silica content and the viscosity of igneous rocks?

<p>Higher silica content leads to higher viscosity. (D)</p> Signup and view all the answers

Which igneous rock is identified as the plutonic equivalent of Basalt?

<p>Gabbro (D)</p> Signup and view all the answers

Which of the following rocks is classified as a felsic plutonic rock?

<p>Granite (B)</p> Signup and view all the answers

Which mineral characteristic affects the order of melting during partial melting?

<p>Silica content of the mineral (A)</p> Signup and view all the answers

Which minerals typically remain solid during the partial melting of granite?

<p>Minerals with lower silica content (C)</p> Signup and view all the answers

In terms of viscosity, how do mafic magmas generally compare to felsic magmas?

<p>Mafic magmas have lower viscosity (D)</p> Signup and view all the answers

What process occurs when some minerals melt while others remain solid?

<p>Partial melting (C)</p> Signup and view all the answers

What determines the type of igneous rocks that form when magma cools?

<p>The original composition of the magma and the environmental conditions (B)</p> Signup and view all the answers

What can the identification of minerals in igneous rocks help geologists understand?

<p>The volcanic history of ancient mountain ranges and modern hazards (A)</p> Signup and view all the answers

What type of magma is likely to erupt more violently?

<p>Magma with a higher percentage of silicon and oxygen (D)</p> Signup and view all the answers

What is a defining characteristic of shield volcanoes?

<p>They are built up by a series of lava flows. (C)</p> Signup and view all the answers

What type of volcano is characterized by a steep triangular profile and more violent eruptions?

<p>Composite volcano (C)</p> Signup and view all the answers

Which type of lava is typically associated with composite volcanoes due to their silica-rich magma?

<p>Viscous lava (B)</p> Signup and view all the answers

How do shield volcanoes generally compare in size to cinder cones?

<p>Much larger in magnitude (D)</p> Signup and view all the answers

What characteristic of lava from shield volcanoes allows it to travel long distances?

<p>It is thin and fluid. (C)</p> Signup and view all the answers

What characteristic hazard can arise from the steep slopes of lava domes?

<p>Pyroclastic flows (A)</p> Signup and view all the answers

Which eruption product is considered the most far-flung during a volcanic eruption?

<p>Tephra (A)</p> Signup and view all the answers

What defines the majority of hazards associated with composite volcanoes?

<p>Tephra, lahars, and pyroclastic flows (C)</p> Signup and view all the answers

Which type of volcano is primarily associated with lava production during eruptions?

<p>Shield volcanoes (A)</p> Signup and view all the answers

What are the characteristics of lahars during a volcanic eruption?

<p>They are fast-moving flows that resemble wet cement. (B)</p> Signup and view all the answers

What is the primary danger associated with pyroclastic flows?

<p>They contain toxic gases and can incinerate anything in their path. (C)</p> Signup and view all the answers

Flashcards

Plutonic Igneous Rocks

Igneous rocks that form when magma cools and solidifies below the Earth's surface.

Volcanic Igneous Rocks

Igneous rocks that form when lava cools and solidifies on Earth's surface.

Texture (of Igneous Rocks)

The size and arrangement of mineral crystals within a rock.

Felsic Igneous Rocks

Refers to rocks with high silica content, typically light-colored.

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Mafic Igneous Rocks

Refers to rocks with low silica content, typically dark-colored.

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Intermediate Igneous Rocks

Refers to rocks with a medium silica content, possessing characteristics of both felsic and mafic rocks.

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Color (as a proxy for silica content)

A visual indicator of silica content in igneous rocks. Light-colored rocks are silica-rich, while dark-colored rocks are silica-poor.

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Silica Content (of Igneous Rocks)

The degree to which a rock is composed of silica (SiO2).

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Silicate Minerals

Minerals that form from cooling magma and are found in igneous rocks.

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Igneous Rock Formation

The process of solidifying magma into igneous rocks.

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Magma Composition

The original composition of magma determines the types of igneous rocks it forms.

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Intrusive Igneous Rocks

Igneous rocks formed deep underground.

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Extrusive Igneous Rocks

Igneous rocks formed on the surface.

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Volcanic Eruptions

Igneous rocks with a high percentage of silicon and oxygen tend to erupt more violently.

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Weathering

The process of breaking down rocks into smaller pieces.

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Erosion

The process of transporting weathered rock fragments.

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Sedimentary Rocks

Rocks formed from cemented together rock fragments.

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Igneous to Sedimentary

The breakdown of igneous rocks creates minerals like quartz and feldspar that form sedimentary rocks.

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Plutonic Texture

A texture in igneous rocks that indicates the rock cooled and crystallized slowly beneath the surface.

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Volcanic Texture

A texture in igneous rocks that indicates the rock cooled and crystallized quickly at the surface.

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Rhyolite

A felsic igneous rock with a volcanic texture. Often appears light colored and fine-grained.

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Granite

A felsic igneous rock with a plutonic texture. Often appears light colored and coarse-grained.

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Andesite

An intermediate igneous rock with a volcanic texture. Often appears gray to brown.

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Diorite

An intermediate igneous rock with a plutonic texture. Often appears gray to dark gray.

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Basalt

A mafic igneous rock with a volcanic texture. Often appears dark gray to black.

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Partial Melting

The process where only some minerals in a rock melt, while others remain solid.

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Multi-mineral Rocks

Rocks made up of different minerals that melt at different temperatures.

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Silica Content and Melting Point

The higher the silica content of a mineral, the lower its melting temperature.

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Partially Melted Magma

Magma formed by partial melting of minerals with higher silica content.

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Peridotite

A type of ultramafic rock found in the Earth's mantle. It has a composition similar to the mantle.

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Amphibole

A type of mineral present in peridotite, some varieties have higher silica content than others.

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Magma Solidification

The process where magma generated from partial melting rises and solidifies to form igneous rocks.

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Petrology

The study of how rocks are formed and how they change over time.

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Oxygen and Silicon

The most abundant elements in Earth's crust, making up 75% of its composition. They are essential building blocks of many minerals and rocks.

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Quartz

A mineral found in granite, composed of only silicon and oxygen. It is often clear or white.

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Feldspar

A type of mineral found in granite, containing additional elements like potassium, sodium, and aluminum. It often has a pink or white color.

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Shield Volcano

A type of volcano with a broad, gently sloping profile, often resembling an overturned shield. Formed by repeated eruptions of thin, fluid lava flows that can travel long distances.

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Composite Volcano

A type of volcano characterized by steep slopes, often forming cone-shaped peaks. Built up by a combination of explosive eruptions and lava flows.

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Explosive Volcanic Eruption

A large volcanic eruption where molten rock, ash, and gases are violently ejected from a volcano.

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Effusive Volcanic Eruption

A volcanic eruption where molten rock flows out of the volcano in a relatively slow and less violent way.

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Volcanic Chain

A series of volcanic eruptions along a specific region, often associated with tectonic plate boundaries.

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Cinder Cone

Small, cone-shaped volcanoes formed by the accumulation of ejected volcanic debris (tephra) and lava.

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Lava Dome

Dome-shaped structures created by the slow extrusion of viscous lava. They can be dangerous as their steep slopes can collapse, releasing pyroclastic flows.

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Tephra

Volcanic debris that is ejected into the air during eruptions. It ranges in size from fine ash to large blocks.

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Volcanic Hazard

Any volcanic process that poses a threat to life, property, or infrastructure.

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Pyroclastic Flows

Hot clouds of toxic gas that tumble down the volcanic slopes.

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What is a lahar?

A fast-moving mixture of water, volcanic debris, and sediment that can travel down valleys with great force, often caused by melting glacial ice or heavy rainfall during an eruption.

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Describe a pyroclastic flow.

Hot, dense clouds of toxic gases and volcanic ash that rush down the slopes of a volcano at high speed, capable of incinerating anything in their path.

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Define an effusive eruption.

A type of eruption where lava flows slowly and steadily from a volcano, building up wide, shield-shaped volcanic structures.

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What is tephra?

Volcanic debris, ranging in size from fine ash to large rocks, that is ejected into the air during eruptions

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What is a lava dome?

A dome-shaped structure formed by the slow extrusion of thick, viscous lava. They often develop inside the crater of composite volcanoes after an eruption, and can be dangerous due to potential collapses.

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Study Notes

Volcanic Hazards

  • Volcanic eruptions are among the most spectacular natural hazards.
  • Hazards are any volcanic process that threatens life or infrastructure.
  • Volcanic eruptions rarely directly consume people; instead, burial by mudflows or hot clouds of toxic gas is more common.
  • Cascade volcanoes have erupted roughly once every 1-2 centuries in the past 4000 years.
  • Volcanic eruptions can be violent or mild, depending on magma viscosity and gas content.
  • Lahars (mudflows) are a significant hazard, can rapidly overwhelm populated areas, and have been responsible for significant loss of life.
  • Tephra (volcanic debris) can cause economic disruption, block transportation routes, and create hazards for aviation.
  • Lahars can be destructive and carry large quantities of debris, snow, ice, and rocks, resulting in significant damage.

Volcano Classification

  • Volcanoes have recognizable characteristics based on their form.
  • Shield volcanoes have gentle slopes from fluid, relatively non-explosive eruptions; composite volcanoes have steep slopes from more violent, explosive eruptions.
  • Cinder cones are much smaller types of volcanoes.
  • Lava domes are smaller, bulbous formations.
  • Composite volcanoes are frequently associated with subduction zones where one tectonic plate slides under another.
  • Shield volcanoes are often associated with hot spots, areas of elevated heat rising from deep within the Earth's mantle.
  • Volcanoes can have varied sizes and shapes.

Magma Viscosity and Gas Content

  • Viscosity, the resistance to flow, depends on temperature and composition.
  • Higher-viscosity magma traps gases, leading to explosive eruptions.
  • Lower-viscosity magma releases gases more easily, resulting in less-violent eruptions, or flows.
  • Magma composition, containing dissolved gases, determines the style of eruptions.
  • Silica content significantly influences magma viscosity. Higher silica content leads to higher viscosity and more explosive eruptions.
  • Water content in magma can also dramatically lower its viscosity and increase explosivity.
  • The amount of dissolved gases in magma also impacts explosivity, increasing dramatically as pressure decreases during ascent.
  • The type of magma, volcanic products, and eruptive style can vary depending on the interaction between magma viscosity and gas content.

How Rocks Melt

  • Temperature and pressure are key in determining melting conditions.
  • Rocks melt at specific temperatures, determined by depth in the earth, and presence of water.
  • There are different types of melting conditions: decompression melting, flux melting, and heat transfer melting.
  • Decompression melting occurs when rocks are released from greater to lesser pressures, causing them to melt, commonly at ridges, and hot spots.
  • Flux melting occurs at subduction zones as water-rich minerals are compressed into the mantle, causing melting of the rocks above.
  • Heat transfer melting occurs when heat from the molten magma transfers to rocks above, causing melting.
  • Melting can occur through decompression melting and flux melting, which are associated with specific geological settings, like oceanic ridges and subduction zones. The presence of water plays a crucial role in flux melting, significantly lowering the melting temperature of rocks.
  • Different melting mechanisms, including decompression melting, flux melting, and heat transfer, affect the formation of magma in varying geological settings. Water plays a key role in lowering the melting temperatures of rocks, particularly at subduction zones.

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Volcanoes and Volcanic Rocks Module (1) PDF

Description

Explore the fascinating world of volcanic hazards and classifications. This quiz covers the characteristics of different types of volcanoes, the dangers they pose, and the factors that influence magma viscosity and gas content. Dive into the science behind eruptions and their impact on life and infrastructure.

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