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

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