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 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.