Bobby Yang, age 10, of Schenectady, New York, for his question:
How does a volcano form?
The patient earth may take a hundred million years to build up a mighty mountain. But the recipe for building a volcano can go much faster. It is true that some of our active volcanoes have been erupting and growing through thousands of years. But a sizeable volcano can form in five years or so. Not so long ago, this actually happened and scien¬tists had a chance to watch it, step by fiery step.
This particular volcano was born early in 1943, in a cornfield about 200 miles west of Mexico City. There had been a lot of earthquakes in the neighborhood—but on February 19 there were 300 of them. The next day, Dionisio Pulido was tending to his cornfield when, to and behold, he saw a plume of steamy smoke coming up from a small hole in the ground.
Some say that Dionisio tried stuffing rocks down the hole. Maybe he did, but certainly it could not stop what was on the way. That night the ground was shaken by explosions and rocks were hurled through the air. Obviously something fierce and fiery was trying to burst forth from deep down in the ground. In the morning, the scared villagers saw that the eruptions had piled up a heap of rubble 100 feet high.
And things got worse in a hurry. Day and night, the young volcano coughed up choking clouds of steamy fumes, rained ashes far and wide, hurled great rocks through the air and erupted rivers of red hot lava. At night the sky was lit with fiery flames from the crater at the top of the tapering cone.
The news soon spread and volcano scientists arrived in a few days to record the astonishing details. Soon Dionisio’s farm was buried, then the whole village of Paricutin.
Still the seething materials kept on erupting from the bowels of the earth. After a year of its seething fury, it was 1,400 feet high. Its red hot lava had wiped out miles of farmlands and villages.
After the first year, the volcano, named Paricutin, slowed down and ten years later it was nothing more than a steep sided cone of volcanic debris. Most volcanoes erupt and rest, erupt and rest—taking centuries to form. But all of them form more or less in the same way.
The cause seems to be far down in the earth, perhaps 30 miles below the surface. We do not know everything there is to know, but most experts suspect that the roots of a volcano reach a buried pocket of molten rock and steamy gases under enormous pressure. When there is a crack or weak section in the crust, the seething mixture erupts—somewhat like a giant sized bottle of pop.
Where there is one volcano, there tend to be others not far away. Most of them are steered in certain parts of the world, where there are deep weak spots, in the earth’s crust. For example, there is a long chain of volcanoes through the Mediterranean. Another chain forms a gigantic circle—around the Pacific Ocean. It is called the Ring of Fire.