Ten Interesting Facts . . . Volcanoes

Mount St. Helens 2005

Mount St. Helens 2005


1.Biggest Volcano

The biggest volcano in our solar system is on Mars. Olympus Mons is 600 km (373 miles) wide and 21 km (13 miles) tall.

2.Most Explosive

Volcanoes are measured by the Volcano Explosivity Index.

VEI Ejecta volume Classification Description Plume Frequency Examples
0 < 10,000 m³ Hawaiian non-explosive < 100 m constant Kilauea
1 > 10,000 m³ Hawaiian / Strombolian gentle 100–1000 m daily Stromboli
2 > 1,000,000 m³ Strombolian / Vulcanian explosive 1–5 km weekly StromboliGaleras, 1992
3 > 10,000,000 m³ Vulcanian / Peléan severe 3–15 km few months Ruiz, 1985
4 > 0.1 km³ Peléan / Plinian cataclysmic 10–25 km ≥ 1 yr Pelée (1902), Eyjafjallajökull (2010)
5 > 1 km³ Plinian paroxysmic 20–35 km ≥ 10 yrs Vesuvius (79) St. Helens (1980)
6 > 10 km³ Plinian / Ultra-Plinian colossal > 30 km ≥ 100 yrs Pinatubo (1991)
7 > 100 km³ Ultra-Plinian mega-colossal > 40 km ≥ 1,000 yrs Tambora (1815)
8 > 1,000 km³ Supervolcanic apocalyptic > 50 km ≥ 10,000 yrs Yellowstone (640,000 BC)

3. Largest Eruptions

Five Largest Volcanic Eruptions in Recent History

Location When Volcanic
Explosivity Index (VEI)
Tambora Sunda Islands,
April 10, 1815 7
Krakatoa Indonesian
island of Krakatoa
Aug. 27, 1883 6
Novarupta Alaska Peninsula June 6, 1912 6
Pinatubo Philippines June 15, 1991 6
Santa Maria Pacific coast of
Oct. 24, 1902 6

4. Locations

Volcanoes may be found on the ocean floor and under the icecaps.

5. Eruptions

Volcanic eruptions can send ash over 30 km (17 miles) into the atmosphere.

6. Effects of Eruptions

Erupting volcanoes can trigger tsunamis, flash floods, earthquakes, mud flows, and rock falls.

7. Locations on Earth

More than half of the 500 active volcanoes found on Earth are in a circle around the Pacific Ocean known as the “Ring of Fire.” The United States has active volcanoes in Hawaii, Alaska, California, Oregon, and Washington.

8. Active, Dormant, and Extinct Volcanoes

Volcanoes can be active, dormant, or extinct. Active means the volcano has had an eruption in the last few thousand years. Dormant means the volcano has the potential to erupt although it hasn’t erupted recently. Extinct means the volcano is not likely to erupt again.

9. Deadliest

The deadliest eruption in what is now the United States took place 200 years ago. Kilauea erupted on the Hawaiian Islands killing more than 400 people.

10.Types of Volcanoes

There are different kinds of volcanoes.

Shield VolcanoShield Volcanoes


When the lava contains less gas, the eruption is gentler. Flow after flow of thin streams of lava flows out in all directions from the volcano’s vent. This creates a flat, dome-shaped mountain with broad slopes.

Lava DomeLava Domes

 Lava domes are formed by small spherical masses of lava. These are too thick to flow. The lava piles around the vent. Lava domes often grow larger by expansion within the volcano.

Composite or strata volcanoes contain a lot of gas mixed in with the lava. Because of the built-up gas, the eruptions are violent. The volcano spews out gases, ash, and hot lava. The lava doesn’t travel far. It piles up creating a volcano that is built of many layers of ash and solidified lava.
CinderCinder Cones
Cinder cones are formed when a volcano violently erupts. The lava quickly congeals and falls around the vent in a circular shape.

 Information Sources

Photo Mount St.Helens

Fun Volcano Facts

11 Facts About Volcanoes

Volcanic Explosivity Index

Five Biggest Volcano Eruptions in Recent History

50 Amazing Volcano Facts

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Ten Interesting Facts . . Volcanoes


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