Volcanic eruptions come in six main types, each with unique characteristics and hazards. From gentle Hawaiian flows to explosive Plinian blasts, these eruptions shape landscapes and pose risks to nearby communities. Understanding their differences is key to predicting and managing volcanic threats.

Monitoring volcanoes involves tracking seismic activity, gas emissions, ground deformation, and other signs of unrest. These methods help scientists forecast eruptions and assess risks. Volcanic hazards include lava flows, pyroclastic currents, ash fall, and lahars, which can devastate surrounding areas and impact global climate.

Volcanic Eruption Types

Classification and Characteristics

• Volcanic eruptions are classified into six main types based on their eruptive style, which is determined by the magma composition, gas content, and other factors influencing the eruption process
• Hawaiʻian eruptions are characterized by effusive, low-viscosity basaltic lava flows and lava fountains, typically resulting in the formation of shield volcanoes and lava lakes
• Strombolian eruptions involve moderate-viscosity magma and are characterized by intermittent explosive bursts of gas and incandescent lava fragments, often forming scoria cones
• Vulcanian eruptions are characterized by short-lived, violent explosions of ash, gas, and fragmented lava, often resulting in the formation of lava domes and pyroclastic density currents

Explosive and Destructive Eruptions

• Pelean eruptions involve high-viscosity, silicic magma and are characterized by the slow extrusion of lava domes, which can collapse and generate pyroclastic density currents and lahars
• Plinian eruptions are the most explosive and destructive type, characterized by sustained, powerful eruption columns that can reach stratospheric heights and disperse large volumes of ash and pumice over vast areas
  • Plinian eruptions are often associated with the formation of calderas and can have global climatic impacts due to the injection of volcanic gases and aerosols into the atmosphere (Mount Pinatubo, 1991)
• Phreatomagmatic eruptions occur when magma interacts with water, resulting in highly explosive, steam-driven eruptions that produce fine ash and form tuff rings or maars (Taal Volcano, 2020)

Volcanic Hazards

Destructive Flows and Falls

• Lava flows are streams of molten rock that can travel significant distances from the vent, causing destruction and burying landscapes, with their impact dependent on the lava's composition, temperature, and flow rate
  • Basaltic lava flows are typically less viscous and faster-moving (Kilauea, Hawaii), while silicic lava flows are more viscous and slower-moving but can still cause significant damage (Chaitén, Chile)
• Pyroclastic density currents (PDCs) are ground-hugging, high-velocity flows of hot ash, pumice, and volcanic gases that can travel at speeds up to 700 km/h and devastate areas up to 100 km from the vent (Mount St. Helens, 1980)
  • PDCs are among the deadliest volcanic hazards, as they can cause asphyxiation, severe burns, and destruction of infrastructure in their path
• Ash fall is the deposition of fine volcanic particles ejected during an explosive eruption, which can accumulate in thick layers and cause respiratory issues, damage to crops and infrastructure, and disruption of transportation networks (Eyjafjallajökull, Iceland, 2010)

Other Hazardous Phenomena

• Volcanic gases, such as sulfur dioxide, carbon dioxide, and hydrogen sulfide, can pose health risks to nearby populations, contribute to acid rain, and impact local air quality
• Lahars are destructive mudflows or debris flows generated by the mixing of volcanic ash, debris, and water, which can travel rapidly down river valleys and cause significant damage to infrastructure and loss of life (Nevado del Ruiz, Colombia, 1985)
• Volcanic earthquakes and ground deformation can cause damage to buildings and infrastructure, trigger landslides, and create hazardous conditions in the vicinity of the volcano

Monitoring Volcanic Activity

Seismic and Gas Monitoring

• Seismic monitoring involves the use of seismometers to detect and analyze earthquakes and other seismic events associated with magma movement and volcanic unrest
  • Changes in the frequency, magnitude, and location of seismic events can provide insights into the likelihood and timing of an impending eruption
• Monitoring volcanic gas emissions, particularly sulfur dioxide, carbon dioxide, and hydrogen sulfide, can provide valuable information about the magma's depth, composition, and degassing processes
  • Increases in gas emissions or changes in the ratios of different gases can indicate rising magma and the potential for an eruption

Deformation, Thermal, and Hydrological Monitoring

• Ground deformation monitoring uses techniques such as GPS, tiltmeters, and satellite radar interferometry (InSAR) to measure the swelling or deflation of the volcano's surface caused by magma intrusion or withdrawal
  • Rapid or accelerating ground deformation can be a sign of imminent eruption, while gradual deformation may indicate long-term changes in the magmatic system
• Thermal monitoring using infrared cameras and satellite imagery can detect heat anomalies associated with lava flows, lava domes, and other volcanic features, providing insights into the volcano's activity level
• Hydrological monitoring of springs, streams, and lakes near the volcano can detect changes in water chemistry, temperature, and flow rates that may be indicative of volcanic unrest
• Integrating data from multiple monitoring techniques and using advanced data analysis and modeling tools can improve the accuracy and timeliness of eruption forecasting and risk assessment

Impacts of Volcanic Eruptions

Human and Infrastructure Impacts

• Volcanic eruptions can cause direct loss of life through exposure to lava flows, pyroclastic density currents, ash fall, and volcanic gases, particularly in populated areas near the volcano
• Destruction of homes, buildings, and critical infrastructure, such as roads, bridges, and power plants, can occur due to lava flows, pyroclastic density currents, lahars, and heavy ash fall, leading to long-term displacement of affected populations and economic losses
• Disruption of transportation networks, including roads, airports, and seaports, can hamper evacuation efforts, emergency response, and the delivery of essential supplies to impacted areas
• Agricultural losses can result from the burial of croplands by ash and lava, contamination of soil and water sources, and damage to irrigation systems, leading to food insecurity and economic hardship for farming communities

Health and Environmental Consequences

• Volcanic ash can cause respiratory issues, eye irritation, and other health problems for exposed populations, particularly those with pre-existing respiratory conditions
  • Ash can also contaminate water supplies, leading to water shortages and the need for extensive water treatment
• Long-term environmental impacts can include changes in local and regional climate, alteration of ecosystems due to the destruction of habitats, and the introduction of new volcanic substrates that may influence soil formation and plant succession
• Secondary hazards, such as wildfires ignited by lava flows or pyroclastic density currents, can cause additional damage to the environment and human infrastructure
• Effective volcanic risk assessment, emergency planning, and public education can help mitigate the potential impacts of volcanic eruptions on human populations and infrastructure, while also promoting resilience and recovery in affected communities