by Janet Spencer

At any given moment, about 20 volcanoes are exploding somewhere round the world. Approximately 350 million people live within “danger range” of an active volcano. Come along with Tidbits as we admire volcanoes from afar!


Yellowstone is actually the crater of an ancient— but still active— volcano. The entire area is rising regularly at the rate of half-inch per year. Yellowstone explodes about once every 600,000 years. The last explosion occurred about 600,000 years ago. When Yellowstone erupted 2 million years ago, it left a hole in the ground larger than Rhode Island.

• Yellowstone is one of about 30 “hot spots” in the Earth’s crust with super-volcano potential.

• The reason potatoes grow so well in Idaho today is because Mt. Mazama erupted 6,600 years ago, spreading mineral-rich ash over the entire area. Today, Mt. Mazama is known as Crater Lake. When the volcano was spent, the empty magma chambers collapsed upon themselves, and the deep volcanic crater filled with water.

• “Magma” is molten rock that’s still underground; “lava” is molten rock that’s been expelled and is above ground.

On April 5, 1815, the Lieutenant Governor of Java in Indonesia heard what he thought was booming cannon fire coming across the ocean. Thinking a ship might be in distress, he immediately dispatched two ships to search the Java Sea to find out what was going on. He also ordered a detachment of troops to march into the city, just in case rebels were attacking a nearby outpost. The ships found nothing during their search and no rebels appeared in town. Days later, news reached Java that the volcanic mountain of Tambora, on an island 750 miles (1,200 km) away, had exploded and destroyed itself. That was the source of the booming.

• When Tambora erupted in Indonesia, the gas and dust circled the globe, causing extreme weather and unusual cold worldwide. A 19-year-old woman named Mary Wollstonecraft Shelley was vacationing in Switzerland that summer. Since it was too cold to go outside to enjoy the mountains, she stayed inside and wrote a novel called “Frankenstein.”

• Global temperatures fell by an average of half a degree Fahrenheit after Mount Pinatubo exploded in 1991. The volcano released some 30 million metric tons of sulfur dioxide into the stratosphere, which are highly reflective and bounced sunlight back into space. The sulfates circulated for about a year before dissipating.

• On August 26, 1883, Krakatoa erupted in Indonesia. It’s thought that an earthquake opened a rift in the side of the volcano which allowed sea water to pour into the magma chambers. This resulted in a series of cataclysmic eruptions and catastrophes that lasted all day, all night, and into the next day. The blast was equal to 3,000 Hiroshima-size atom bombs, and 18 times more powerful than the Mount Saint Helens blast. It’s said to have been the loudest sound ever heard on Earth since humans have been around.

The cinder cone volcano Paricutin appeared in a Mexican cornfield on February 20, 1943. Within a week it was 5 stories tall, and by the end of a year it had grown to more than 1,100 feet (336 m) tall. It ended its growth in 1952, at a height of 1,391 feet (424 m).

• In El Salvador, the mountain called Volcan Izalco had been erupting almost constantly for years. The government decided money could be made by opening the place to tourists. So they declared it a national park, paved a road, built a hotel, a bar, and a restaurant, and announced the grand opening. As the ribbons were being cut, the volcano stopped erupting. It has been quiet ever since.


In 1973 the Helgafell volcano off the coast of Iceland began erupting. The 5,300 residents of the island were evacuated, but 300 people stayed to try to save the town from the slowly advancing lava. The 120 foot tall (37 m) 1,000 foot wide (305 m) wall of lava threatened to seal off the town’s only harbor, ruining many industries that depended on access to the ocean, killing the town.

• In desperation, their fire engines pumped water on the advancing flow. Small tongues of lava solidified under the steady barrage of water, and a small dam built up, slowing the flow. Then a sand dredger with Iceland’s most powerful pumps started throwing sea water onto the flow. Workers found that by piping the water to a point behind the flow’s front, a series of small dams formed internal barriers in the flow. Plastic pipes laid on top of the hot rock would not melt as long as water continued to flow through them.

• 19 miles (30 km) of pipes and 43 pumps were used to pump water for nearly four months straight. Finally the volcano settled down. The harbor— and most of the town— had been saved.


There is a hot spot in the earth’s crust under Hawaii, which allows magma to escape, building new land. The hot spot remains in one place, but continental drift causes the plate of the earth’s crust to slowly float over it. This has resulted in the building up of Hawaii’s chain of islands one at a time.

• The volcanic mountain named Mauna Loa in Hawaii is the tallest mountain in the world if you include the part that’s submerged beneath the sea. It’s about 30,000 feet (91 km) tall from sea floor to peak (that’s 5.6 miles), and it’s still growing. Mt. Everest is only 26,000 feet (9 km) tall.

• Kilauea Crater in Hawaii is one of the world’s most active volcanoes, erupting regularly about once a month. The sugar cane fields belonging to the Ola Sugar Co. were being destroyed by a advancing lava. Their New York insurance company refused to pay for damages, saying that the crop was insured against fire, not lava. The Ola Sugar Co. insisted a claims agent fly out to Hawaii to look at the situation. The agent, never having seen a lava flow, was very nervous as he was driven closer and closer to the lava. It was explained to him as he became increasingly frightened, that the heat from the advancing lava first burned the crop before covering it. As a fountain of lava roared up near the car, the agent agreed to pay the claim if only they would drive him away from the place!


“Volcano” comes from Vulcan, the Roman god of fire. “Crater” is Latin for “cup.”

• “Lava” comes from the Latin word meaning “to wash” which also gives us “lavage” and “lavatory.” The word originally meant a downpour of rain that washed the streets clean, but then came to mean a flow of melted rock that scoured the mountainside clean of plants and trees.