How Does a Volcano form?

In February, 1943, in the middle of a cornfield in Mexico, people saw a rare and amazing thing taking place. A volcano was being born ! In three months it had formed a cone about 300 metres high. Two towns were destroyed and a wide area damaged by the falling ash and cinders.

What makes a volcano form? The temperature under the earth becomes higher and deeper you go. At a depth of about 20 miles, it is hot enough to melt most rocks.

When rocks melts, it expands and needs more space. In certain areas of the world, mountains are being uplifted. The pressure becomes less under these rising mountains ranges, and a reservoir of melted rock ( called "magma" ) may form under them.

This material rises along cracks formed by the uplift. When the pressure in the reservoir is greater than the roof of rock over it, it bursts fourth as a volcano.

In eruption, hot gaseous liquid, or solid material blown out. The material piles up around the opening, and a cone-shaped mound is formed. The "crater" is depression at the top of the cone where the opening reaches the surface. The cone is he result of a volcano.

The material coming out of a volcano is mainly gaseous, but large quantities of "lave" and solid particles that look like cinders and ash are also thrown out.

Actually, lava is magma that have been thrown up by the volcano. When the magma comes near the surface, the temperature and the pressure drop, and a physical and chemical change takes place that changes the magma to lava.