Volcanic Eruption

A geological phenomenon in which underground magma erupts onto the surface, causing widespread damage and climatic effects through volcanic ash, lava, and volcanic gases.

Volcanic Eruption

Overview

A volcanic eruption (火山噴火, volcanic eruption) is a geological phenomenon in which magma from the Earth's interior, along with volcanic gases and pyroclastic material, is ejected through fissures or vents on the surface. It occurs mainly at plate boundaries or above hot spots, and depending on the volume and nature of the erupted material, the scale of damage can range from tens of kilometers to global proportions. An eruption is both a disaster that destroys the surface environment and a natural process that decisively influences atmospheric composition, climate, soil fertility, and landform formation.

Main Content

1. Principles of Eruption

Magma generated at depths of 10–100 km beneath the surface rises because it is less dense than the surrounding rock. Magma accumulated in a magma chamber contains dissolved gases (water vapor, carbon dioxide, sulfur dioxide, etc.), and when pressure decreases, these gases expand and form bubbles. The moment this pressure exceeds the strength of the rock, a sudden eruption occurs along with fault rupture. Before and after an eruption, precursor phenomena such as volcanic earthquakes, surface deformation (inflation and deflation), geothermal anomalies, and changes in gas emission rates appear, making these the key clues for prediction.

2. Types of Eruption

The form varies according to lava viscosity and gas content.

Hawaiian: Low-viscosity basaltic lava flows quietly. Explosivity is low.
Strombolian: Characterized by regular intermittent eruptions and lava fountains.
Vulcanian: Highly viscous lava and ash clouds are ejected in short, violent bursts.
Plinian: The highest level of explosive eruption, in which large amounts of volcanic ash and pumice are ejected from a stratovolcano into the stratosphere.
Phreatic (steam) eruption: Magma does not emerge directly; instead, groundwater meets hot rock and causes a steam explosion.

3. Volcanic Explosivity Index (VEI)

Eruptions are classified from 0 to 8 based on the volume of erupted material and the height of the eruption column. A VEI 4 or higher can scatter volcanic ash several kilometers away and paralyze air traffic, while super-eruptions of VEI 7–8 trigger a "volcanic winter" effect that lowers global temperatures by 0.5–1°C for several years. The 1815 eruption of Tambora in Indonesia (VEI 7) is a representative case that caused a "Year Without a Summer" in Europe and North America the following year, leading to famine.

4. Major Eruption Cases

The 79 AD eruption of Mount Vesuvius in Italy buried Pompeii.
The 1883 eruption of Krakatoa caused more than 36,000 deaths and generated a global atmospheric pressure wave.
The 1980 eruption of Mount St. Helens in the United States caused its north slope to collapse and generated large-scale pyroclastic flows.
The 2010 eruption of Eyjafjallajökull in Iceland canceled more than 100,000 European flights.
The 2022 eruption of the Hunga Tonga–Hunga Haʻapai submarine volcano recorded the largest atmospheric shock wave ever observed by satellite.

5. Impacts and Damage

Direct damage includes lava flows, pyroclastic flows (hot avalanches), volcanic mudflows (lahars), volcanic ashfall, and volcanic gas poisoning. Volcanic ash can cause respiratory diseases and stall aircraft jet engines, making it one of the greatest variables in aviation safety. Indirectly, it leads to reduced solar radiation due to stratospheric aerosols, ozone depletion, and decreased agricultural production. On the other hand, volcanic regions also provide economic benefits such as geothermal power generation, hot spring tourism, and fertile volcanic soil.

6. Monitoring and Prediction

Modern volcanology combines seismometers, GPS and InSAR surface deformation observations, satellite thermal infrared imagery, volcanic gas spectroscopy, and drone and robot-based close-range observation. However, quantitative prediction of eruption timing and scale remains a difficult problem, and most efforts remain at the level of presenting probabilistic scenarios.

Recent Trends

From 2023 to 2025, continuous eruptions occurred near Grindavík on Iceland's Reykjanes Peninsula, making resident evacuation and protection of geothermal infrastructure major issues, and the accuracy of magma dike modeling improved significantly. In 2024–2025, machine learning-based volcanic earthquake classification and deep learning volcanic ash dispersion prediction models were introduced into practical use and linked with air traffic control. As satellite constellations (CubeSats) and permanent SAR observation systems expand, gaps in the monitoring of submarine and remote volcanoes are tending to decrease. On the Korean Peninsula, research on the magma chamber beneath the caldera of Mount Baekdu and the seismic and gas monitoring network continue to be expanded, and as of 2025, operation of volcanic ash damage response manuals and an aviation detour route consultative body has become routine. In addition, international joint observation projects are actively underway to quantify the effects of volcanic eruptions on short-term climate change and the ozone layer.