Volcanic Eruptions and Magma Types
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Questions and Answers

What type of eruption may produce explosive clouds of hot ash and transition into plumes termed eruption columns?

Highly viscous, silica-rich magmas

What type of volcano does Mauna Loa represent?

  • Composite cone volcano
  • Shield volcano (correct)
  • Caldera
  • Stratovolcano

    • Match the following types of calderas with their descriptions:

    Crater Lake-Type Calderas = 1. Exceed 1km in diameter Hawaiian-Type Calderas = 2. Eruptions on the sides (flanks) of volcanoes that extrude lava that produce small features Yellowstone-Type Calderas = 3. Map of the extent of the ashfalls for the last 3 caldera-forming eruptions of Yellowstone

    The Ring of Fire is located around the Atlantic Ocean.

    <p>False</p> Signup and view all the answers

    Where are volcanoes of the deep-ocean basin primarily located?

    <p>Divergent plate boundaries</p> Signup and view all the answers

    What was the date of the Mount St. Helens eruption?

    <p>Sunday, May 18, 1980</p> Signup and view all the answers

    What was the impact on the elevation of Mount St. Helens after the eruption?

    <p>It decreased by over 1350 feet.</p> Signup and view all the answers

    How many lives were lost in the Mount St. Helens eruption?

    <p>59</p> Signup and view all the answers

    What was the area affected by the flattening of trees?

    <p>400 km2</p> Signup and view all the answers

    How far did the mudflows flow down the Toutle River?

    <p>18 miles</p> Signup and view all the answers

    What was the height ash was blown into the atmosphere?

    <p>11 miles</p> Signup and view all the answers

    What is characteristic of the eruption of Hawaii's Kilauea volcano?

    <p>Quiet eruptions with fluid, basaltic lava</p> Signup and view all the answers

    What factors contribute to whether a volcano erupts gently or violently?

    <p>The magma's composition and temperature</p> Signup and view all the answers

    What is the main factor affecting the magma's viscosity?

    <p>Chemical composition</p> Signup and view all the answers

    What happens to the magma's mobility when it cools and begins to solidify?

    <p>It decreases</p> Signup and view all the answers

    What is the effect of water dissolved in magma on its viscosity?

    <p>It decreases its viscosity</p> Signup and view all the answers

    What type of magma is associated with violent eruptions?

    <p>Granitic magma</p> Signup and view all the answers

    What happens to the dissolved gases in magma when it rises to the Earth's surface?

    <p>They expand and form bubbles</p> Signup and view all the answers

    What is the characteristic of highly viscous, silica-rich magmas?

    <p>They may produce explosive clouds of hot ash</p> Signup and view all the answers

    What percentage of lava on Earth has a basaltic composition?

    <p>90%</p> Signup and view all the answers

    What is the main characteristic of basaltic lava flows?

    <p>They are very fluid and fast</p> Signup and view all the answers

    What happens to the lava's viscosity when it reaches the Earth's surface and loses its volatiles?

    <p>It increases</p> Signup and view all the answers

    What is the result of the collapse of a volcano's flank?

    <p>An explosive eruption</p> Signup and view all the answers

    What is a common feature of volcanic activity?

    <p>Long periods of inactivity</p> Signup and view all the answers

    What is the term for a funnel-shaped depression at the summit of most volcanoes?

    <p>Crater</p> Signup and view all the answers

    What type of volcanoes are generated from the accumulation of fluid basaltic lavas?

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

    What is the characteristic shape of shield volcanoes?

    <p>Broad and slightly domed</p> Signup and view all the answers

    What is unique about Mauna Loa?

    <p>It is the largest volcano on Earth</p> Signup and view all the answers

    What is the name of the volcano located on the island of Hawaii in the shadow of Mauna Loa?

    <p>Kilauea</p> Signup and view all the answers

    What is the characteristic of the eruption style of shield volcanoes?

    <p>Quiet and gentle</p> Signup and view all the answers

    What is the term for small features that extrude lava on the sides of volcanoes?

    <p>Parasitic cones</p> Signup and view all the answers

    What is the name of the region where most volcanic activity occurs on Mauna Loa?

    <p>East Rift Zone</p> Signup and view all the answers

    What is unique about the Paricutin volcano?

    <p>It is one of the few volcanoes that has been observed from initial eruption to extinction</p> Signup and view all the answers

    What is the composition of the magma that typically generates composite volcanoes?

    <p>Andesitic</p> Signup and view all the answers

    What is the name of the type of flow that covered much of the town of San Juan Parangaricutiro?

    <p>Aa flow</p> Signup and view all the answers

    Where are most composite volcanoes located?

    <p>In a narrow zone surrounding the Pacific Ocean</p> Signup and view all the answers

    What is the name of the type of volcano that is the most abundant type of major volcanic types?

    <p>Cinder cone volcano</p> Signup and view all the answers

    What is the typical size range of cinder cones?

    <p>100-1,000 feet in elevation</p> Signup and view all the answers

    What is the name of the type of flow that can develop associated with the explosive eruption of composite cones?

    <p>Pyroclastic flow</p> Signup and view all the answers

    What is the characteristic of the magma that generates composite volcanoes?

    <p>Thick and viscous</p> Signup and view all the answers

    What is the name of the volcano that erupted in 1980 in the United States?

    <p>Mount St. Helens</p> Signup and view all the answers

    What is the typical velocity of lahars?

    <p>3-5 m/sec</p> Signup and view all the answers

    What is the name of the volcano that erupted in 1902, causing the destruction of the town of St. Pierre?

    <p>Mount Pele</p> Signup and view all the answers

    What is the name of the lake that formed in a caldera in Oregon?

    <p>Crater Lake</p> Signup and view all the answers

    What is the depth of Crater Lake?

    <p>3,800 feet</p> Signup and view all the answers

    What is the name of the type of caldera that forms due to the collapse of a shield volcano?

    <p>Hawaiian-type</p> Signup and view all the answers

    What is the name of the volcano that erupted in 1985, causing lahars that flowed down three river valleys?

    <p>Nevado del Ruiz</p> Signup and view all the answers

    What is the typical distance that pyroclastic flows can travel from their source?

    <p>60 miles</p> Signup and view all the answers

    What is the name of the volcano that erupted in 1980, causing lahars that flowed down the Toutle River?

    <p>Mount St. Helens</p> Signup and view all the answers

    What is the name of the small cinder cone that formed in Crater Lake?

    <p>Wizard Island</p> Signup and view all the answers

    How many people survived the eruption of Mount Pele in 1902?

    <p>1</p> Signup and view all the answers

    What is the primary source of magma generation?

    <p>Partial melting of rocks</p> Signup and view all the answers

    What is the term for the process where rocks melt at higher temperatures at depth due to greater confining pressures?

    <p>Pressure-induced melting</p> Signup and view all the answers

    What role does water content play in determining the temperature at which a rock will melt?

    <p>Decreases the melting temperature</p> Signup and view all the answers

    What is the estimated temperature at the core-mantle boundary?

    <p>4,500°C</p> Signup and view all the answers

    What is the term for the change in temperature with depth in the Earth's crust?

    <p>Geothermal gradient</p> Signup and view all the answers

    What type of magma is generated when basaltic magma rises and 'ponds' beneath crustal rocks?

    <p>Silica-rich</p> Signup and view all the answers

    What is the primary location of volcanoes of the deep-ocean basin?

    <p>Mid-ocean ridges</p> Signup and view all the answers

    What is the effect of increasing confining pressures on a rock's melting temperature?

    <p>It increases the melting temperature</p> Signup and view all the answers

    What is the role of heat in the generation of magma?

    <p>It lowers the melting temperature of rocks</p> Signup and view all the answers

    What is the term for the process where a rock ascends due to convective upwelling, resulting in decompression melting?

    <p>Decompression melting</p> Signup and view all the answers

    What is the name of the geologic rock formation that is 1,200 feet thick in some locations, produced by the ash deposit of the Yellowstone super-eruption?

    <p>Lava Creek Tuff</p> Signup and view all the answers

    What type of volcanic activity is associated with the largest volume of volcanic material being extruded?

    <p>Fissure eruptions</p> Signup and view all the answers

    What is the term used to describe the low-viscosity basaltic lava that can cover a large geographic area?

    <p>Flood basalts</p> Signup and view all the answers

    What type of geologic structure is formed when magma is injected into fractures that cut across rock layers?

    <p>Dike</p> Signup and view all the answers

    What is the term used to describe the tabular bodies of magma that are injected along sedimentary bedding surfaces?

    <p>Sills</p> Signup and view all the answers

    What is the characteristic of magma that allows it to stay molten long enough to flow 90 miles from its source?

    <p>Low viscosity</p> Signup and view all the answers

    What is the term used to describe the largest intrusive igneous bodies?

    <p>Batholiths</p> Signup and view all the answers

    What is the term used to describe the volcanic necks that form when the rock of the volcanic pipe is more resistant to weathering than the surrounding pyroclastic material?

    <p>Volcanic necks</p> Signup and view all the answers

    What is the term used to describe the geologic structures that form when magma is injected into fractures that cut across rock layers, resulting in a lens-shaped mass that arches the overlying strata upward?

    <p>Laccoliths</p> Signup and view all the answers

    What is the term used to describe the smaller intrusive bodies that are similar to batholiths?

    <p>Stocks</p> Signup and view all the answers

    What is a characteristic of pahoehoe flows?

    <p>They have higher temperatures than aa flows.</p> Signup and view all the answers

    What is the purpose of lava tubes?

    <p>They allow for lava to flow great distances from its source.</p> Signup and view all the answers

    What is the composition of gases in magma?

    <p>Water vapor (70%), carbon dioxide (15%), nitrogen (5%), and smaller amounts of chlorine, hydrogen, and argon.</p> Signup and view all the answers

    What is the result of high temperatures of magma?

    <p>The magma generates cracks.</p> Signup and view all the answers

    What is the term for particles produced as gases expand and blow pulverized rock, lava, and glass fragments?

    <p>Pyroclastic material</p> Signup and view all the answers

    What is an example of a volcanic landform that is produced from intermittent volcanic activity over hundreds of thousands of years?

    <p>Mt. Hood</p> Signup and view all the answers

    What is the term for vesicular ejecta with a basaltic composition?

    <p>Scoria</p> Signup and view all the answers

    What is the result of gases rising with magma?

    <p>The gases expand, creating larger cracks.</p> Signup and view all the answers

    What is the term for particles larger than lapilli made of incandescent lava?

    <p>Bombs</p> Signup and view all the answers

    What is the percentage of gases in magma by weight?

    <p>1% to 6%</p> Signup and view all the answers

    What is the primary reason for the melting of mantle rocks, generating magma, in the context of plate tectonics?

    <p>Decompression</p> Signup and view all the answers

    What type of magma is typically generated along convergent plate boundaries?

    <p>Basaltic</p> Signup and view all the answers

    What is the term used to describe the process of mantle rocks melting due to a reduction in overlying pressure?

    <p>Decompression melting</p> Signup and view all the answers

    What is the characteristic of volcanic arcs formed when oceanic crust subducts beneath continental lithosphere?

    <p>They have a high concentration of volatiles</p> Signup and view all the answers

    What is the characteristic of intraplate volcanic activity?

    <p>It results from excessively hot mantle material rising to the surface</p> Signup and view all the answers

    What is the term used to describe the area in which basaltic magma erupts due to intraplate activity?

    <p>Hot spot</p> Signup and view all the answers

    What is the characteristic of the magma generated at mid-ocean ridges?

    <p>It is of basaltic composition</p> Signup and view all the answers

    What is the result of the melting of mantle rocks in the context of plate tectonics?

    <p>The generation of magma</p> Signup and view all the answers

    What is the primary location of volcanic activity along divergent plate boundaries?

    <p>Mid-ocean ridges</p> Signup and view all the answers

    What is the characteristic of the magma generated in the environment of continental volcanic arcs?

    <p>It is of andesitic or granitic composition</p> Signup and view all the answers

    Study Notes

    Types of Volcanic Eruptions

    • Highly viscous, silica-rich magmas may produce explosive clouds of hot ash and transition into plumes termed eruption columns.

    Anatomy of a Volcano

    • A composite cone volcano can exceed 1km in diameter and are termed calderas.
    • Eruptions on the sides (flanks) of volcanoes can produce small features that extrude lava.

    Famous Volcanoes

    • Mauna Loa and Kilauea are examples of volcanoes.
    • Paricutin is a volcano in Mexico.

    Types of Calderas

    • Crater Lake-Type Calderas, Hawaiian-Type Calderas, and Yellowstone-Type Calderas are three types of calderas.

    Yellowstone Caldera

    • The map shows the extent of the ashfalls for the last 3 caldera-forming eruptions of Yellowstone.

    Flood Basalts

    • The Columbia Plateau has an illustration of the extent of flood basalts.

    Arizona Palisades Sill

    • An example of a sill.

    Factors Affecting Volcanic Eruptions

    • The role of heat, pressure, and volatiles can affect volcanic eruptions.
    • The introduction of water can lower the melting points by as much as 100° C.

    Global Distribution of Volcanoes

    • The Ring of Fire is located around the Pacific Ocean.
    • Volcanoes can also be found in the deep-ocean basin and irregularly distributed on the interiors of continents.
    • Convergent Plate Boundaries and Divergent Plate Boundaries can also affect the distribution of volcanoes.

    Here are the study notes:

    Volcanic Eruptions

    • Mount St. Helens Eruption (1980)
      • Largest human-recorded volcanic eruption in North America
      • 59 lives lost
      • Entire north flank of the volcano blown out, lowering elevation by 1350 feet
      • Trees flattened within a 400 km2 area
      • Mudflows flowed 18 miles down the Toutle River
      • Nearly one cubic kilometer of ash and debris ejected
      • Ash cloud reached 11 miles into the atmosphere
      • Ash fallout was over 2 meters deep in the immediate area
      • Measurable ash deposits developed in Oklahoma and Minnesota
      • Crops damaged as far east as Montana

    Types of Volcanic Eruptions

    • Quietest Eruptions (Kilauea, Hawaii)
      • Fluid, basaltic lava flows
      • Occasional lava fountains
      • Over 180 homes destroyed since 1983
    • Violent Eruptions (Mount St. Helens)
      • More silica-rich magma, thicker and more viscous
      • Greater gas content leading to more explosive eruptions

    Factors Affecting Eruptions

    • Magma Composition
      • Affects viscosity and explosivity
    • Magma Temperature
      • Affects viscosity and mobility
    • Dissolved Gases
      • Affects viscosity and explosivity

    Lava Flows

    • Basaltic Lava
      • Hot, fluid, and fast-moving (up to 19 mph)
      • Forms in thin, broad sheets or channel-like flows
    • Andesitic/Rhyolitic Lava
      • Cooler, thicker, and slower-moving
      • Shorter flow distances
    • Lava Tubes
      • Form when lava flows beneath the surface
      • Allow lava to flow long distances from its source

    Gas Content and Volcanic Activity

    • Gas Content in Magma
      • Affects explosivity and viscosity
      • Analysis of recent eruptions in Hawaii: water vapor (70%), carbon dioxide (15%), nitrogen (5%), and smaller amounts of chlorine, hydrogen, and argon
    • Volcanic Gases
      • Propel magma from a volcano
      • Generate large gas plumes that rise high into the atmosphere

    Anatomy of a Volcano

    • Shield Volcanoes
      • Broad, gently sloping structures
      • Formed from accumulation of fluid basaltic lavas
      • Examples: Hawaii, Iceland, Galapagos
    • Cinder Cones
      • Small, steep-sided structures
      • Formed from ejected lava fragments
      • Examples: Paricutin, Mexico
    • Composite Cones
      • Large, symmetrical structures
      • Formed from lava and pyroclastic deposits
      • Examples: Mount St. Helens, Mount Rainier, Mount Fuji

    Pyroclastic Flows and Lahars

    • Pyroclastic Flows
      • Hot ash, dust, and gases that flow down volcano flanks
      • Can reach speeds of up to 125 mph
    • Lahars
      • Volcanic mudflows that form when volcanic debris becomes saturated with water
      • Can form during heavy rainfall or snow/ice melting

    Calderas and Volcanic Landforms

    • Crater Lake-Type Calderas
      • Form from collapse of the composite cone summit after an explosive eruption
      • Example: Crater Lake, Oregon
    • Hawaiian-Type Calderas
      • Form from gradual subsidence as magma drains laterally from the magma chamber
      • Examples: Mauna Loa and Kilauea### Yellowstone-Type Calderas
    • 630,000 years ago, Yellowstone erupted 1,000 km3 of pyroclastic material, creating a caldera 43 miles across.
    • The eruption deposited ash as far away as the Gulf of Mexico.
    • The ash deposit formed the Lava Creek Tuff, which is 1,200 feet thick in some locations.
    • Magma accumulation led to pressure on the overlying rock, causing gas-rich magma to produce vertical fractures and a ring of eruptions.
    • The center of the ring collapsed, forcing more magma to the surface.
    • This process produces the largest calderas.
    • Three caldera-forming episodes have occurred in the Yellowstone region over the last 2.1 million years.

    Volcanic Activity

    • Volcanic activity is not only associated with volcanoes.
    • The largest volume of volcanic material is extruded through fractures in the Earth's crust, called fissures.
    • Fissures produce low-viscosity basaltic lava that can cover a large geographic area.
    • Examples of flood basalts include the Columbia Plateau (western US), Deccan Trapps (India), and Ontong Java Plateau (Pacific Ocean floor).

    Volcanic Pipes and Necks

    • Volcanoes on land are continually weathered and eroded.
    • The rock of the volcanic pipe is more resistant to weathering than the surrounding pyroclastic material.
    • This results in the pipe standing above the surrounding terrain, forming a volcanic neck.
    • Examples include Shiprock, New Mexico.

    Igneous Rocks

    • Volcanic eruptions receive most of the media attention, but most magma crystallizes inside the Earth's surface.
    • These geologic structures are called plutons.
    • Tectonic activity and erosion can expose plutons above the Earth's surface.
    • Plutons vary in size and shape and can be classified as tabular or massive.

    Dikes and Sills

    • Dikes are sheet-like bodies produced when magma is injected into fractures that cut across rock layers.
    • Sills are tabular plutons formed when magma is injected along sedimentary bedding surfaces.
    • Both dikes and sills can have a significant impact on the surrounding rock.

    Igneous Batholiths

    • Batholiths are intrusive bodies with a surface exposure of more than 100 km2.
    • They are by far the largest intrusive igneous bodies.
    • Batholiths are typically discordant and can be hundreds of kilometers long and wide.

    Magma Generation

    • Seismological evidence indicates that the Earth's crust and upper mantle are composed primarily of solid rock.
    • Magma generation occurs through partial melting of existing rocks.
    • The melting point of a rock is a function of three factors: heat, pressure, and volatiles.
    • The geothermal gradient increases with depth, with temperatures reaching 1,200°C to 1,400°C at 100 km within the Earth.

    Distribution of Volcanic Activity

    • The global distribution of volcanic activity is not random and falls within three general groups:
      • Ring of Fire (around the Pacific Ocean)
      • Volcanoes of the deep-ocean basin
      • Irregularly distributed on the interiors of continents
    • The distribution of volcanoes is connected to plate tectonics.

    Plate Tectonics and Volcanic Activity

    • Plate motion provides the mechanism necessary to result in the melting of mantle rocks, generating magma.
    • Three zones of volcanic activity and plate boundaries:
      • Convergent plate boundaries
      • Divergent plate boundaries
      • Areas not associated with plate boundaries (intraplate activity)

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    Description

    This quiz covers volcanic eruptions, magma types, and their characteristics. Topics include the effects of silica-rich magmas and the formation of eruption columns.

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