1. A mountain opens downward toward a pool of molten rock, which is called magma. This all happens below the surface of the earth. So a volcano is essentially hole in the Earth from which molten rock and gas erupt.
2. The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology.
3. As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up through fissures, which are narrow cracks in the earths crust. Once the magma erupts through the earth’s surface it’s called lava.
4. Magma is liquid rock inside a volcano. Fresh lava ranges from 1,300° to 2,200° F (700° to 1,200° C) in temperature and glows red hot to white hot as it flows.
5. There are around 1,510 active volcanoes in the world. We currently know of 80 or more which are under the oceans. At any given time, there is an average of about 20 volcanoes that are erupting.
6. The Earth's crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. When two plates collide, one section slides on top of the other, the one beneath is pushed down. Magma is squeezed
7. Volcanoes are like giant safety valves that release the pressure that builds up inside the Earth.
8. Over half of the world’s volcanoes arise in a belt around the Pacific Ocean called the Ring of Fire.
9. The largest volcano (and mountain) in our Solar System is Olympus Mons on the planet Mars. The volcano is 17 miles (27 km) tall and over 320 miles (520 km) across.
10. Mauna Loa is one of the five volcanoes that form the island of Hawaii. It is 60 miles long and 30 miles wide, it makes up half of the entire island. Mauna Loa, and Kilauea are the only active volcanoes. Mount St. Helens, in the state of Washington, is one of more than 65 active or potentially active volcanoes in the continental United States, Alaska, and Hawaii. Only Indonesia and Japan have more!