How much new land is formed each year because of volcanoes?

Emily Vaughan

Dear Emily,

Volcanoes add new land both vertically (by adding layers on the old land surface) and horizontally (by extending the coast of islands and continents). I don't think anyone has tried to measure how much new land is created each year on a global scale. We can look at some numbers add maybe get some idea of what is added.

In an average year eruptions with VEI>2 add about 42 million cubic meters of tephra to the land each year. This would cover and area 1 km on a side 42 m deep or square six city blocks on each side 140 feet deep. Typically, tephra is a thin deposit that covers a large area (with these numbers that is about 10 square miles buried 6 inches deep). These estimates are minimums. They do not include big eruptions that happen once every 10, 100, or 10,000 years. The largest eruptions (the ones that happen every 100,000 years), like Yellowstone, can produce 600 square miles (2,500 cubic km) of ash that cover areas as large as the western United States. This rough estimate does not include lava flows.

More than 500 acres (200 hectometers) of new land has been added to the island of Hawaii since 1983. There are 640 acres to a square mile. So that is an estimate for islands above hot spots.

Thanks for a good question.

Steve Mattox, University of North Dakota

Source of Information:

Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience=20 Press, Tucson, Arizona, 349 p.

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