Incredible Volcanoes!

Underground, DEEP, DEEP, DEEP underground in the earth's crust, rocks can get SO HOT that they MELT!

This molten rock (magma) sometimes reaches the surface. When it does it is called: "lava". After the lava and magma cool, they harden and form volcanic rocks of incredible shapes and sizes.

Most volcanoes are cone-shaped mountains ("cinder cone" volcanoes) made of many layers of cool hardened lava. (There are also "shield" volcanoes which have a rounder top and "composite" volcanoes which are a combination of a cinder-cone volcano and a shield volcano). A volcano grows during cycles. As a volcano erupts, lava shoots out of the hole and flows down the sides of the forming volcano.

Then it becomes solid and VOILA! --> the volcano has grown!

Volcanic rocks are really igneous "extrusive" rocks. Extrusive igneous rocks are formed when magma (molten rock underground) erupts from a volcano as lava and then cools at the earth's surface. The other type of igneous rocks are "intrusive" which first solidify and cool within the earth's crust and appear at the surface after all the other rocks above them have eroded away.

Some of the rocks that form from volcanic activity are incredible. There are volcanic bombs which are blobs of lava thrown out of a volcano and solidify in the air!

Another two rocks that form when lava cools very quickly are pitchstone and obsidian. Check them out!

But the far most common extrusive rock is basalt.

If you would like to find out more about volcanoes, go check out this site on the web . . .

Visit Volcano World!