Volcanology

🌋Volcanology Unit 1 – Volcanology: Earth's Fiery Structure

Volcanology explores Earth's fiery underbelly, studying how volcanoes form, behave, and impact our world. From shield volcanoes to explosive stratovolcanoes, this field examines diverse volcanic structures, eruption types, and the complex interplay of magma composition and behavior. Volcanic hazards like pyroclastic flows and lahars pose significant risks to communities. Scientists use various monitoring techniques to predict eruptions and assess risks. Volcanoes also play a crucial role in shaping landscapes, influencing climate, and even creating fertile soils that support life.

Key Concepts and Terminology

  • Volcanology studies the formation, behavior, and effects of volcanoes and volcanic phenomena
  • Magma molten rock beneath Earth's surface consists of liquid rock, crystals, and dissolved gases
  • Lava magma that reaches the surface during a volcanic eruption can flow and solidify into various formations
  • Volcanic arc chain of volcanoes formed by subduction of oceanic plates beneath continental or other oceanic plates (Aleutian Islands)
  • Pyroclastic flow fast-moving, ground-hugging avalanche of hot ash, pumice, rock fragments, and volcanic gas (Mount Vesuvius eruption in 79 AD)
  • Lahar volcanic mudflow or debris flow composed of volcanic ash, rock, and water from a volcano (Nevado del Ruiz eruption in 1985)
    • Can be triggered by heavy rainfall, rapid snowmelt, or collapse of a volcanic dam
  • Caldera large circular depression formed by the collapse of a volcano's summit or the emptying of its magma chamber (Yellowstone Caldera)
  • Fumarole opening in or near a volcano that emits steam and volcanic gases (Sulphur Springs in St. Lucia)

Types of Volcanoes and Eruptions

  • Shield volcanoes broad, gently sloping volcanoes built from fluid lava flows (Mauna Loa in Hawaii)
    • Produce effusive eruptions with low-viscosity lava that can flow great distances
  • Stratovolcanoes tall, conical volcanoes composed of layers of lava, ash, and pyroclastic debris (Mount Fuji in Japan)
    • Often associated with explosive eruptions due to high-viscosity lava and gas buildup
  • Cinder cone volcanoes small, steep-sided volcanoes built from accumulations of ejected lava fragments (Parícutin in Mexico)
  • Lava domes rounded, steep-sided mounds formed by viscous lava piling up around a volcanic vent (Lassen Peak in California)
  • Phreatic eruptions steam-driven explosions that occur when water comes into contact with hot rock or magma (Taal Volcano in the Philippines)
  • Plinian eruptions violent, explosive eruptions characterized by tall eruption columns and widespread ash dispersal (Mount Vesuvius eruption in 79 AD)
  • Strombolian eruptions moderate-sized explosions that eject incandescent cinders, lapilli, and lava bombs (Stromboli in Italy)
    • Named after the Italian volcano Stromboli, known for its frequent, mildly explosive eruptions

Volcanic Structures and Formations

  • Volcanic plug solidified magma that fills and seals the conduit of a volcano (Ship Rock in New Mexico)
  • Lava tubes cave-like structures formed by the drainage of lava beneath the hardened surface of a lava flow (Thurston Lava Tube in Hawaii)
  • Lava plateaus extensive, flat areas of solidified lava formed by large-scale effusive eruptions (Columbia River Basalt Province)
  • Volcanic necks erosional remnants of the central vent or plug of a volcano (Devil's Tower in Wyoming)
  • Columnar jointing distinctive pattern of hexagonal columns formed by the contraction of cooling lava (Giant's Causeway in Northern Ireland)
  • Maar broad, shallow volcanic crater formed by a phreatic or phreatomagmatic eruption (Crater Elegante in Mexico)
    • Often filled with water to form a crater lake
  • Fumarolic fields areas with numerous fumaroles and hydrothermal activity (Bumpass Hell in Lassen Volcanic National Park)
  • Lava trees vertical molds formed when lava flows around and solidifies around tree trunks (Lava Tree State Park in Hawaii)

Magma Composition and Behavior

  • Magma composition influences volcanic behavior and eruption style through variations in silica content, viscosity, and gas content
  • Mafic magma low-silica, high-temperature magma that produces fluid lava flows and effusive eruptions (basaltic magma)
    • Associated with shield volcanoes and lava plateaus
  • Felsic magma high-silica, lower-temperature magma that generates viscous lava flows and explosive eruptions (rhyolitic magma)
    • Often found in stratovolcanoes and lava domes
  • Magma viscosity measure of a magma's resistance to flow determined by silica content, temperature, and dissolved gas content
    • Higher viscosity magmas tend to trap gases, leading to explosive eruptions
  • Magma differentiation process by which magma composition evolves due to crystallization and removal of minerals (fractional crystallization)
  • Magma mixing blending of two or more magmas of different compositions, which can trigger volcanic eruptions
  • Volatiles dissolved gases in magma (water vapor, carbon dioxide, sulfur dioxide) that exsolve and expand as magma rises and decompresses
    • Contributes to the explosivity of volcanic eruptions
  • Magma chamber large underground pool of magma beneath a volcano that feeds volcanic eruptions (Yellowstone magma chamber)

Monitoring and Predicting Volcanic Activity

  • Seismic monitoring detection and analysis of earthquakes and seismic waves to assess volcanic activity and potential eruptions
    • Volcanic tremor continuous, rhythmic seismic signal often preceding or accompanying volcanic eruptions
  • Ground deformation measurements of changes in the shape of a volcano's surface using GPS, tiltmeters, and satellite radar interferometry (InSAR)
    • Inflation of a volcano can indicate magma accumulation and increased eruption potential
  • Gas monitoring sampling and analysis of volcanic gases to determine changes in magma chemistry and degassing (sulfur dioxide, carbon dioxide)
    • Increased gas emissions often precede volcanic eruptions
  • Remote sensing use of satellite imagery, thermal imaging, and other techniques to detect surface temperature changes and ash plumes
  • Lahar detection systems networks of acoustic flow monitors, trip wires, and rain gauges to provide early warning of lahars
  • Eruption precursors observable phenomena that often precede volcanic eruptions (increased seismicity, ground deformation, gas emissions)
    • Used in combination to assess the likelihood and timing of an eruption
  • Hazard mapping creation of maps that delineate areas potentially affected by volcanic hazards (lava flows, pyroclastic flows, ash fall)
    • Essential for risk assessment and emergency planning

Hazards and Risk Assessment

  • Pyroclastic flows fast-moving, ground-hugging avalanches of hot ash, pumice, rock fragments, and volcanic gas (Mount Pelee eruption in 1902)
    • Can travel at speeds up to 700 km/h and reach temperatures of 1,000°C
  • Lava flows streams of molten rock that pour from a volcano during an effusive eruption (Kilauea eruption in 2018)
    • Can destroy infrastructure and reshape landscapes but generally move slowly enough for people to evacuate
  • Volcanic ash fine particles of pulverized rock and glass ejected during an explosive eruption (Mount St. Helens eruption in 1980)
    • Can cause respiratory problems, damage aircraft engines, and collapse roofs under heavy accumulation
  • Volcanic gases emissions of water vapor, carbon dioxide, sulfur dioxide, and other gases from volcanoes
    • Can cause acid rain, air pollution, and contribute to climate change
  • Lahars volcanic mudflows or debris flows composed of volcanic ash, rock, and water from a volcano (Nevado del Ruiz eruption in 1985)
    • Can travel great distances, inundate valleys, and destroy infrastructure
  • Volcanic tsunamis waves generated by the displacement of water during a volcanic eruption or flank collapse (Krakatoa eruption in 1883)
  • Volcanic edifice collapse sudden failure and downslope movement of a volcano's flank or summit (Mount St. Helens eruption in 1980)
    • Can generate debris avalanches, lahars, and lateral blasts
  • Risk assessment evaluation of the potential impacts and likelihood of volcanic hazards on communities and infrastructure
    • Considers factors such as population exposure, vulnerability, and resilience

Environmental and Climate Impacts

  • Volcanic ash and aerosols can affect climate by reflecting solar radiation and promoting atmospheric cooling (Mount Pinatubo eruption in 1991)
    • Sulfur dioxide emissions can lead to the formation of sulfuric acid droplets in the stratosphere
  • Volcanic CO2 emissions contribute to greenhouse gas concentrations and long-term climate change
    • Volcanoes release an estimated 180 to 440 million tonnes of CO2 per year
  • Volcanic eruptions can cause short-term regional cooling and global temperature fluctuations (Laki eruption in 1783)
    • Injection of ash and sulfur dioxide into the upper atmosphere can disrupt weather patterns
  • Volcanic soils weathering of volcanic ash and rocks can create fertile soils rich in nutrients (Andisols)
    • Support diverse ecosystems and agricultural productivity in volcanic regions
  • Hydrothermal systems networks of hot springs, geysers, and fumaroles associated with volcanic activity (Yellowstone hydrothermal system)
    • Host unique thermophilic microbial communities and provide geothermal energy resources
  • Volcanic lakes water-filled volcanic craters that can host endemic species and provide water resources (Crater Lake in Oregon)
    • Can also pose hazards such as lake overturn and limnic eruptions due to dissolved gas accumulation
  • Volcanic island formation creation of new land by submarine or subaerial volcanic eruptions (Surtsey in Iceland)
    • Contributes to the growth and evolution of oceanic islands and archipelagos

Notable Volcanoes and Case Studies

  • Mount Vesuvius (Italy) infamous for its catastrophic eruption in 79 AD that buried the Roman cities of Pompeii and Herculaneum
    • Provides a valuable archaeological record of Roman life and the impacts of volcanic eruptions
  • Krakatoa (Indonesia) explosive eruption in 1883 generated devastating tsunamis and global climate effects
    • Collapse of the volcanic edifice created a 6-km-wide caldera and new volcanic islands
  • Mount St. Helens (USA) major eruption in 1980 featuring a massive debris avalanche, lateral blast, and ash column
    • Significant ecological disturbance and recovery, now a natural laboratory for studying volcanic processes
  • Kilauea (Hawaii) one of the world's most active volcanoes, known for its continuous effusive eruptions and lava flows
    • Eruptions have added over 500 acres of new land to the island of Hawaii since 1983
  • Yellowstone Caldera (USA) largest volcanic system in North America, characterized by extensive hydrothermal activity and geysers
    • Potential for future supereruptions, though the likelihood is low on human timescales
  • Mount Pinatubo (Philippines) major eruption in 1991 that injected large amounts of sulfur dioxide into the stratosphere
    • Caused global temperature drop of 0.6°C and disrupted global weather patterns for several years
  • Eyjafjallajökull (Iceland) eruption in 2010 that disrupted air travel across Europe due to the widespread dispersal of volcanic ash
    • Highlighted the vulnerability of modern transportation systems to volcanic hazards
  • Nevado del Ruiz (Colombia) eruption in 1985 triggered destructive lahars that killed over 23,000 people in the town of Armero
    • Emphasized the importance of volcano monitoring, hazard mapping, and early warning systems


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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.