Volcanos

Volcanos


This paper will define and discuss the volcano to include: types of
volcanoes, formation of a volcano, and elements of a volcano; such as, lava,
rock fragments, and gas. This paper also tells a little bit about volcanic
activity in different parts of the world.

What is a volcano?

A volcano is a vent in the earth from which molten rock and gas erupt.
The molten rock that erupts from the volcano forms a hill or mountain around the
vent. The lava may flow out as a viscous liquid or it may explode from the vent
as solid or liquid particles.

Kinds of Volcanic Materials

Three basic materials that may erupt from a volcano are; 1. lava, 2.
rock fragments, and 3. gas.


Lava

Lava is the name for magma that has been released onto the Earth's
surface. When lava comes to the Earth's surface, it is red hot and may have
temperatures of more than 2012 degrees Fahrenheit. Fluid lava flows swiftly down
a volcano's slopes. Sticky lava flows more slowly. As the lava cools, it may
harden into many different formations. Highly fluid lava hardens into smooth,
folded sheets of rock called pahoehoe. Stickier lava cools into rough, jagged
sheets of rock called aa.   Pahoehoe and aa cover large areas of Hawaii, where
the terms originated. The stickiest lava forms flows of boulders and rubble
called block flows. It may also form mounds of lava called domes.

Other lava formations are spatter cones and lava tubes. Spatter cones
are steep hills that can get up to 100 feet high. They build up from the spatter
of geyser-like eruptions of thick lava. Lava tubes are tunnels formed from fluid
lava. As the lava flows, its exterior covering cools and hardens. But the lava
below continues to flow. After the flowing lava drains away, it leaves a tunnel.

Rock Fragments

Rock fragment are usually called tephra and are formed from sticky magma.
This magma is so sticky that its gas can not easily escape when the magma
approaches the surface or central vent. Finally, the trapped gas... [continues]

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