VOLCANOES

Mount Vesuvius (Italy) – 79 AD

• Located on the Campanian volcanic arc.
• Formed by the subduction of the African Plate under the Eurasian Plate.
• Classified as a stratovolcano.
• Experienced a Plinian eruption.
• Ejected molten rock, pumice, and gas at 1.5 million tons per second.
• Pyroclastic flows incinerated Pompeii and Herculaneum.
• Over 16,000 fatalities resulted.
• Dormant for several centuries before the 79 AD eruption.
• Likely reawakened due to magma accumulation and tectonic stress.
• Has erupted dozens of times since, with the last eruption in 1944.
• Currently closely monitored.
• Pliny the Younger's records provide a detailed eyewitness account.
• The modern hazard includes Naples, with approximately 3 million people nearby.

Huaynaputina (Peru) – 1600

• Part of the Andean Volcanic Belt.
• Formed by the subduction of the Nazca Plate beneath South America.
• Eruption was a VEI 6 (Volcanic Explosivity Index).
• Ash spread across the globe.
• Triggered climate anomalies, including famines in Russia and harsh winters in Europe and Asia.
• No major eruptions occurred for centuries prior.
• Reawakened likely due to tectonic magma injection.
• Still considered active, and geothermal activity continues.
• An estimated 2 million deaths occurred globally, mostly indirectly via famine.
• Little remains of the original summit, which collapsed into a caldera.

Mount Unzen (Japan) – 1991

• Located on the Pacific Ring of Fire at a convergent plate boundary.
• Classified as a lava dome complex.
• Dormant since 1792.
• Seismic swarms and phreatic explosions signaled magma intrusion in 1990–91.
• Pyroclastic flows in 1991 killed 43 people, including volcanologists Katia and Maurice Krafft.
• Earthquakes and ground deformation preceded the eruption.
• Magma rich in silica created thick, sticky lava prone to explosive activity.
• An excellent case study in volcano monitoring.
• Led to a greater understanding of lava dome collapse and flow dynamics.

Mount Tambora (Indonesia) – 1815

• Formed from the subduction of the Indo-Australian Plate beneath the Eurasian Plate.
• Classified as a stratovolcano.
• Eruption was VEI 7, one of the most powerful in recorded history.
• Exploded with the force of 1000 Hiroshima bombs.
• Produced global ash fallout and a 43 km-high plume.
• Immediate deaths numbered around 12,000.
• Indirect deaths (famine, disease) numbered around 80,000.
• Dormant for centuries before 1815.
• Massive magma accumulation occurred beneath the caldera.
• Reawakened explosively, losing 1,400 meters of summit.
• Caused “The Year Without a Summer” in 1816.
• Resulted in famines and crop failures in North America and Europe.
• Inspired works like Mary Shelley's Frankenstein.

Krakatoa (Indonesia) – 1883

• Located in the Sunda Strait between Java and Sumatra.
• Formed by the subduction of the Indo-Australian Plate.
• Began with earthquakes and small eruptions in May 1883.
• The final explosion (August 27) was VEI 6, one of the loudest sounds in recorded history.
• Collapsed into a caldera, triggering tsunamis up to 40m high.
• Dormant for over 200 years.
• Built up gas-rich magma over time.
• Explosive pressure resulted from the interaction of magma with seawater.
• Killed over 36,000 people, mostly from tsunamis.
• Ash darkened skies worldwide, and global temperatures dropped.
• The child volcano Anak Krakatoa (“Child of Krakatoa”) began forming in 1927.

Lake Nyos (Cameroon) – 1986

• A volcanic crater lake on the Cameroon Volcanic Line.
• Magma beneath the lake leaks CO₂, which dissolves into the water.
• Not a volcanic eruption but a limnic eruption (gas burst).
• CO₂-rich water suddenly overturned (possibly due to landslide), releasing 100,000–300,000 tons of CO₂.
• Killed 1,746 people and 3,500 livestock in surrounding valleys.
• The lake had been building up CO₂ over decades.
• A small disturbance (like a landslide or rainfall) disrupted lake stratification.
• Gas release suffocated people silently.
• Led to the development of degassing tubes to prevent future disasters.
• Raised awareness about CO₂ hazards in volcanic lakes.

Mount St. Helens (USA) – 1980

• Part of the Cascade Range.
• Formed by the subduction of the Juan de Fuca Plate under the North American Plate.
• Classified as a stratovolcano.
• Precursors included earthquakes and bulging of the north flank.
• On May 18, an earthquake triggered a lateral blast as the bulge collapsed.
• Largest landslide in recorded history occurred, along with a vertical eruption.
• Dormant since 1857.
• Rising magma, gas accumulation, and hydrothermal activity signaled reawakening.
• Resulted in 57 deaths and $1.1 billion in damage.
• Transformed the landscape, creating a new dome and crater.
• A benchmark for modern volcano science.

Eyjafjallajökull (Iceland) – 2010

• Sits atop the Mid-Atlantic Ridge and under a glacier.
• Classified as a glaciovolcano (subglacial eruptions).
• March 2010: effusive phase, minor lava.
• April: explosive due to magma-ice interaction.
• Fine ash was ejected high into the atmosphere.
• Last erupted in 1821–23.
• Reawakened due to tectonic spreading and magma intrusion.
• Increased seismicity and melting were detected weeks before.
• Air travel across Europe was grounded for over a week.
• Global cost exceeded $5 billion.
• Demonstrated the global reach of even moderate eruptions.

Hunga Tonga–Hunga Haʻapai (Tonga) – 2022

• A submarine volcano in the Tonga-Kermadec Arc.
• Convergent boundary: Pacific Plate subducting under the Indo-Australian Plate.
• VEI 5–6: massive underwater explosion.
• Shockwaves circled the globe multiple times.
• Tsunami waves occurred across the Pacific, along with satellite disruptions.
• Previous activity in 2014–15 built new land.
• Increased venting was observed in 2021.
• Reawakened with a massive magma-seawater explosion.
• Destroyed the island, and ash covered Tonga.
• The greatest atmospheric explosion since Krakatoa.

Yellowstone Caldera (USA) – Dormant Supervolcano

• A continental hotspot system.
• Gigantic magma chamber beneath Yellowstone National Park.
• Three major eruptions occurred: 2.1M, 1.3M, and 640k years ago.
• Ejected thousands of cubic kilometers of ash.
• Created a caldera approximately 45 miles across.
• No eruption in 640,000+ years, but geothermal activity continues.
• Uplift, gas emissions, and thousands of small earthquakes are monitored constantly.
• Considered active but dormant.
• A potential eruption would be catastrophic, with global climate effects and massive destruction.
• Regular monitoring is conducted via GPS, gas sensors, and seismometers.