Donald Marotto, age 13, of Staten Island,'., for his question:
Why are there so many volcanoes around the Pacific?
The vast Pacific ocean covers almost half the globe. It was named the Pacific because its gentle waters seem calm and peaceful when compared with the heaving waves of the Atlantic. But the shorelines of the great ocean are restless with shifting islands, growing mountains and volcanic activity. Its basin is an awesome bite deep into the earth’s crust.
The shores of the Pacific reach from the north to the south polar regions and its width swallows almost half of the equator. Its average depth is about three miles and the floor of the deep basin is gouged with still deeper pits, ridged with mountains and dotted with lonely undersea hills. No one knows the number of islands in the Pacific and around its shores.
The rim of the great ocean is ringed with mountain ranges and arcs of islands, with earthquake faults and belts of volcanic activity, This restless region has been called the earth’s Ring of Fire and several theories have been suggested to explain it. One theory suggests that the floor of the Pacific is rotating, taking about three billion years to make one turn while its shorelines remain stationary.
Another theory suggests that the Ring of Fire is caused by convection currents deep in the earths interior. On a small scale, a convection current occurs when you boil a pot of soup. The soup at the bottom, getting the most heat, rises in a current at the center of the pot. There it turns towards the edges of the pot and plunges down the sides to start another convection cycle. Convection currents on a vast scale may operate deep in the earth.
If this is so, the Pacific area could be a huge commotion cell with currents rising and descending loop in the globe. The motion is perhaps a few inches a year, but this energy would be enough to explain the restless, mountain making, earthquakes and volcanism around the Pacific. A host of new facts about the earths crust were gathered during the IGY, but scientists are still groping for a theory to fit all the facts together. The convection theory seems the most likely explanation for the Pacific’s Ring of Fire .. but more facts are needed to prove it right or wrong.
The lithosphere is the rocky crust of the earth, 20 to 40 miles thick. Below is the mantle, more dense and almost 2,000 miles thick. Convection currents may arise in the intense heat and pressure of the mantle or even deeper. Currents rising from below would 'Wend to push up the crustal blocks of the lithosphere and descending currents would tend to suck them down. Where rising and falling currents brush each other, the lithosphere would be kept in a state of restless turmoil.