Jimmy Murray, age 12, of Atlanta, Georgia, for his question:
How does a volcano erupt?
Most of the worlds volcanoes are in mountainous regions near the sea. The famous ring of fire is a necklace of volcanoes, some active, some dormant and some extinct, running clear around the shores of the Pacific Ocean. These fire mountains are named for Vulcan, ancient god of fire and blaeksmithing. Each one is a mighty forge, hot enough to melt rock. The hammer of the forge is seething steam, powerful enough to beat a tunnel through 20 to 40 miles of surface rock
Mountain regions are weak areas in the earths crust where great slabs and layers of rocks push up, crack and buckle. Volcanoes seem to occur where there are weaknesses, stresses and strains in the huge layers which form the earths s crust. Their roots may be 20 to 40 miles below the surface. The deeper we go into the earths crust, the hotter it becomes. In areas of stress and strain, the deep layers are hotter than normal.
In certain deep regions, we have pockets of melted rock called magma. All sorts of gases are dissolved in the molten rock but, because of the pressure from the rocks above, it is hidden, just as the gas in soda pop is hidden so long as the cap is on the bottle. From time to time, the buried reservoir of magma goes into action. The seething rocks melt the roof above them. Water trapped in the pores of the rooks becomes superheated steam. This steam explodes and hammers a path upward to the surface.
This is the vent which connects the deep pool of magma to the outside air. The cap is now off the soda bottle. Gases come pouring up and more vents are hammered through the crust rocks.
The pressure is now off the pool of molten magma and up it surges. The volcano erupts.
The molten rock pours forth in a red hot river and the first thing it does is to change its name. It is called lava] from an older word meaning to flow. Magma is coined from an older word meaning t o squeeze. As a rule, a volcano erupts with flame and fury. Explosions and changes in the rocks below ground often cause earthquakes. Steam, smoke, cinders and dust of all kinds is pitched miles into the air. Hot cinders and seething lumps of rock are tossed far and wide. Rivers of red hot molten lava pour over the land. In a single day, an erupting volcano may pour forth 16,000 tons of water vapor and 100,000 tons of lava.
Though every volcano erupts from deep underground, each one is different. Different minerals are in the lava and some have more gas bubbles than others. The cooled lava may become granites, pumice or dark basalt. It may set in ropy twists or solid foam, After countless ages of weathering, lava rocks form fertile soils.