Volcanoes

Volcanoes are awesome manifestations of the fiery power contained deep within the Earth. These formations are essentially vents on the Earth's surface where molten rock, debris, and gases from the planet's interior are emitted.

When thick magma and large amounts of gas build up under the surface, eruptions can be explosive, expelling lava, rocks and ash into the air. Less gas and more viscous magma usually mean a less dramatic eruption, often causing streams of lava to ooze from the vent.

The mountain-like mounds that we associate with volcanoes are what remain after the material spewed during eruptions has collected and hardened around the vent. This can happen over a period of weeks or many millions of years.

There are four kinds of volcanoes that have been discovered on earth and in our solar system:

The shield volcano: This volcano is formed from fluid basaltic magma. The explosions made by this volcano are generally less violent than those of other volcanoes. These volcanoes are generally also smaller and flatter than other volcanoes.

The cinder cone: These volcanoes are fomed by basaltic and andesitic magma, and they are named cinder cones because they blow ash into the sky. Eruptions from these volcanoes tend to contain a lot of gas.

The dome: This is a shorter, rounder volcano formed by viscous dacite magma. This volcano has smaller eruptions but more lava flow than the typical volcano.

The stratovolcano: This volcano is the most dangerous kind, due to its huge size and height. Formed by andesite and dacite lava, this volcano tends to be extremely dangerous. Firestorms, mud flows and pyroclastic flows are all caused by this type of volcano.

The caldera: This is a generally dry, extinct volcano formed near or in water.

In conclusion, there are many different kinds of volcanoes. Through these holes in the earth, we can get a better glimpse of what is going on beneath our feet. While volcanoes are less active now than they were at the earth's formation, they can still pose a threat to humans. With new research and geological equipment, however, perhaps we will soon be able to harness the power of the volcano and use our knowledge to keep ourselves, and thriving ecosystems, safe.

http://volcano.oregonstate.edu/education/index.html
www.hotfact.com/facts-about-volcano.html