The Volcanic Explosivity Index (VEI) rates eruptions on a scale that starts at 0, and the biggest eruptions in history are rated 8. The 1815 eruption of Mount Tambora in Indonesia was the largest volcanic explosion in recorded history.

The 1783 Laki eruption in Iceland came from a fissure 27 kilometers long. It was one of the largest lava eruptions in historic times.

Yellowstone has had three huge caldera-forming eruptions in the past 2.1 million years. They were separated by gaps of roughly 600,000 to 800,000 years.

Volcanoes also erupt under the sea. Lava that erupts under water often piles into rounded mounds called pillow lava.

Volcanic eruptions can cause tsunamis when a volcano is near a large body of water.

Ash can melt inside a jet engine and make the engine stall or fail. Wind can carry ash hundreds of miles from the volcano.

As of November 2026, a Kilauea eruption in 2018 in Hawaii added about 875 acres of new land to the island.

After the 1883 eruption of Krakatau, sunsets and the sky took on unusual colors around the world.

Many of Earth's volcanoes and earthquakes are found along the Ring of Fire, a path that partly circles the Pacific Ocean.

Volcanoes can build whole chains of islands, like the Hawaiian Islands.

The Hawaiian Islands formed over a hot spot: the Pacific Plate slowly carries volcanoes away from it, so the chain gets older in one direction.

When lava flows out and cools, it hardens into solid rock. Basalt, the dark rock that forms from runny lava, makes up most of the ocean floor.

Before Mount Pinatubo's big eruption in June 1991, scientists made forecasts and recommendations. They led to more than 60,000 people being evacuated from around the volcano in the Philippines.

Words to know

• explosivity: explosive strength
• fissure: long crack
• evacuated: moved away
• pillow: rounded lava mound