Ten Interesting Facts . . . Volcanoes

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

Volcano	Location	When	Volcanic Explosivity Index (VEI)
Tambora	Sunda Islands, Indonesia	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 Guatemala	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 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 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

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.

Cinder Cones