How Volcanoes Change the World

Most volcanic explosions are local events, but Earth’s volcanic system has produced global changes from the start. In fact, an Earth without volcanoes would be a pretty lonely place.


	Digging Deeper Find out more about
who Vulcan was and where he lived.

Very early in the planet’s history, massive and frequent eruptions created the vital conditions for life to exist. The explosions freed carbon dioxide and other gases that were in the ground to form an atmosphere. The atmosphere held in heat and allowed rain to fall. Fueled by the Sun and carbon dioxide—the process of photosynthesis—plants thrived. Volcanoes fertilized those plants by spreading ash, which is rich in nutrients—phosphorus, potassium, and magnesium.

Today, volcanic lands are still some of the most fertile lands on Earth. Farmers risk living in the shadow of a volcano to yield productive crops—which explains why volcanic areas can be surprisingly populous.

Towns have been built close to volcanoes
Photo courtesy of volunteer Andrew Cutts.

In many parts of the world cities and towns have been built close to volcanoes. On the island of Lipari, the volcanoes are relatively quiet, so the residents have built houses further and further up the mountain.
As with Anak Krakatau, the “child” of Krakatau, volcanoes are constantly producing new land—new ocean floors, islands, and extensions of coastlines. In Hawaii, as hot lava meets seawater, it explodes into tiny bits, creating beautiful black beaches.

Towns have been built close to volcanoes Photo courtesy of volunteer Jenni James Jayne.

The hot lava from Hawaii’s volcanoes is cooled instantly when it reaches the ocean, causing it to explode into little sandy bits. This creates the famous black sand of the island.

Towns have been built close to volcanoes
Photo courtesy of volunteer Yoko Morikami.

The direction of the ash plume from Japan’indicates the larger direction of the winds in that area.

Volcanoes also help regulate Earth’s global climate. In contrast to global warming, massive explosions like Krakatau or Pinatubo cool the planet for a few years. They unleash high clouds of ash and dust that circle in the upper atmosphere, blocking some of the Sun’s energy.

That ash can disrupt the modern world in other ways. Airplanes flying through clouds of volcanic ash can stall, as the engines get clogged with debris. Because of this, flights may be grounded. Iceland’s Eyjafjallajokull volcano, located under a glacier, erupted on April 13, 2010, and sent large plumes of ash airborne. However, many airplanes fly across Iceland as they travel from Europe to North America, and on to other destinations around the world. Because of the danger of clogged engines, these flights were cancelled for days, forcing major disruptions in world air travel.

The products of volcanoes are useful. Volcanoes move diamonds and metals toward the surface. Galeras in Colombia even spit up gold! Countries such as Iceland depend on volcanoes to provide geothermal energy—drawing heat from the natural furnaces below ground.

Finally, don’t underestimate the power of beauty. Volcanoes are some of the most stunning natural wonders on Earth.

Major Volcanic Eruptions in History
Date	Volcano	What happened
79 CE	Vesuvius, Italy	Eruption of falling ash, pumice, and rocks buries Pompeii, and lahars (mudflows generated by volcanic eruptions) engulf Herculaneum; 3,360 die.
1586	Kelut (Kelud), Java, Indonesia	Lava erupting into the crater lake breaks through side of mountain, causing lahars; approximately 10,000 die.
1669	Mount Etna, Sicily	A series of eruptions generates an enormous lava flow, which destroys 16 villages and a small portion of the city of Catania.
1754	Taal, Philippines	Major eruption destroys the towns of Taal, Sala, Lipa, and Tanauan. The towns are moved to new locations.
1783	Laki, or Lakagigar, Iceland	Eight-month eruption generates poisonous gases and a thick haze that kills crops and livestock, and interrupts fishing on surrounding ocean. Most of Iceland’s livestock die from eating contaminated grass; about one-fourth of the people die from starvation.
1792	Mount Unzen, Japan	A post-eruption earthquake causes old lava dome to collapse into the sea. This causes a huge rock avalanche and a tsunami; 15,000 people are killed.
1815	Tambora, Sumbawa, Indonesia	The largest volcanic eruption in historic time produces ash covering a wide area. The falling ash kills crops, causing the starvation deaths of about 90,000 people. The fine ash circulates the globe and is likely responsible for the “year without summer” in 1816 in Europe and North America—cold weather into June, weak sunlight, crop failures.
1877	Cotopaxi, Ecuador	The world's highest active volcano erupts, causing snow and ice on summit to melt. This produces lahars that travel 100 km (60 mi) from the volcano; about 1,000 die.
1883	Krakatau, Indonesia	In the most violent volcanic eruption in historic time, two-thirds of the island is destroyed. The eruption and subsequent earthquakes and tsunamis kill 36,417.
1902	La Soufrière, St. Vincent, West Indies	Violent eruptions cause nuées ardentes that kill 1,680.
1902	Mount Pelée, Martinique	Hours after eruption in nearby St. Vincent, an eruption heats the water in the crater lake, causing the rim to fail. This sends hot water and pyroclastic debris hurdling down the mountain, causing nuées ardentes that destroy city of St. Pierre; 29,025 are killed.
1912	Novarupta and Katmai, Alaska	The eruption of 21 cu km (5 cu mi) of volcanic material, largest eruption of the 20^th century, at Novarupta causes the collapse of the nearby Katmai volcano, creating a huge caldera.
1919	Kelut (Kelud), Java, Indonesia	Eruption causes the crater lake, boiling from volcanic activity, to break through side of mountain, causing lahars and destroying 104 villages and part of city of Blitar. Over 5,100 people are killed.
1943	Paricutín, Mexico	Scoria cone builds in a farmer’s field, with Strombolian eruptions until 1952.
1951	Lamington, Papua New Guinea	Pyroclastic flows devastate the region around the volcano, causing 3,000 deaths.
1980	Mount St. Helens, Washington, United States	Immediately following an earthquake, a massive eruption sends tons of ash and debris into the sky and blows off north face of mountain. The surrounding forest is leveled and 65 people are killed.
1982	El Chichón, Mexico	Three explosive eruptions produce a giant crater, and send out pyroclastic flows and surges that destroy numerous nearby villages, killing about 2,000 people. Large volumes of sulfur dioxide in lower stratosphere are dispersed globally, producing brilliant sunrises and sunsets.
1985	Nevado de Ruiz, Colombia	Eruption creates lahars that bury most of town of Armero and devastate Chinchiná. About 25,000 people die.
1991	Mount Pinatubo, Philippines	Second-largest eruption of the 20^th century sends ash cloud into the stratosphere. Subsequent lahars deposit ash and debris, causing roof collapses and at least 300 deaths. Environmental impact from ash cloud circulating in the atmosphere felt for years.

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