EXPLAINER - Why volcanoes erupt, and what we’ve learned from 10 years of fire and ash

Volcanoes can ground planes, bury towns, and reshape landscapes in hours. With over 850 eruptions since 2015, Earth is constantly reminding us of its raw power, but why does it erupt, and what can we expect next?

 What causes an eruption?

Volcanoes act as channels allowing magma (molten rock) to reach Earth’s surface. As magma rises, dissolved gases expand, increasing pressure until the rock breaks. Whether an eruption gently flows or explosively bursts depends on magma viscosity and gas content.

“Volcanic eruptions are really about pressure release. Gas wants to escape, and the magma is its vehicle,” — Dr. Jessica Johnson, volcanologist.

“It’s like shaking a soda bottle and releasing the cap too fast—it blows,” — Dr. Janine Krippner, Smithsonian volcanologist.

 Where and how they form?

Most eruptions occur at tectonic plate boundaries, especially subduction zones like the Ring of Fire, or at hotspots such as the Hawaiian Islands. Volcanoes also form along ocean ridges beneath the sea.

Volcanoes types:

• Stratovolcanoes: tall, explosive (e.g., Fuji)
• Shield volcanoes: broad, flowing lava (e.g., Mauna Loa)
• Calderas/Supervolcanoes: summit collapses after massive eruption (e.g., Yellowstone)

“Supervolcanoes like Yellowstone can erupt over 1,000 km³ of material,” said Professor Ray Cas, Monash University.

Major eruptions (2015–2025)

Recorded global eruptions totaled roughly 850+, from minor flows to devastating explosions. Here are the most significant:

 Earthquake-triggered volcanism in Russia

• On July 29, 2025, an M 8.8 megathrust earthquake struck off the Kamchatka Peninsula, generating Pacific-wide tsunami alerts.
• Within days, Krasheninnikov Volcano erupted, its first in six centuries, sending ash 6 km into the sky. Scientists from Russia’s Institute of Volcanology said the quake “activated magmatic centers, pumped additional energy into them.”
• Meanwhile, Klyuchevskaya Sopka, Kamchatka’s tallest and most active volcano, also erupted soon after, suggesting a seismic-volcanic link.

 Why it matters

• On any given day, around 40–50 volcanoes may erupt; globally, that's roughly 850+ eruptions in a decade.
• Large eruptions like VEI 5–6 can disrupt flights, climate, and local populations. Examples: Tonga (2022) and Lewotobi (2024–25).
• Earthquake-triggered eruptions—such as Krasheninnikov following the 8.8 quake, highlight how tectonic shocks can awaken long-dormant volcanoes.
• Monitoring seismic activity is vital for anticipating volcanic behavior, especially in densely active zones like Indonesia, Kamchatka, and Japan.

Quick facts

850+ eruptions (2015–2025), but only one VEI 5–6 event (Tonga)
Average of 40–50 eruptions daily
Earthquakes can trigger nearby volcanoes if conditions are primed
Indonesia and Kamchatka were hotspots of outbreak activity
Avalanche, ash inhalation, toxic gas, and climate cooling are key impacts

 Final word

Volcanoes are critical to understanding Earth’s dynamism, but they are also unpredictable. The 2025 Kamchatka earthquake and subsequent eruption at Krasheninnikov illustrate just how connected the planet’s tectonic systems truly are.

“With seismic activity, you can’t say volcanoes follow a schedule—but you can see the strings connecting them,”
— Dr. Ed Venzke, Smithsonian Institution Global Volcanism Program.

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