Volcanoes

Volcanoes



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by Jacaranda Lopez
Submitted to Instructor Hutchinson
GE101 Fall 2003

Introduction
A volcano is a location on the surface of the Earth where magma has eruptedout of the interior of the planet. Magma is molten rock, which has melted from the extreme heat (2200C to 5000C) and pressure that exists inside the Earth. Once molten rock has erupted onto the Earth’ssurface, it is called lava. As lava spreads out on the surface, it cools and becomes solid rock again. The buildup of lava forms hills and mountains on land, and it forms islands if the volcano beganon the ocean floor. The Hawaiian Islands, for example, exist because of volcanoes.
Volcano Facts
Stages of Volcanic Activity
Volcanoes are classified as active or inactive. Inactive volcanoes areolder and have usually erupted many times. A volcano is described as active if it is currently erupting or expected to erupt eventually.
Eruption Stage
A volcanic eruption occurs when lava, gasses,and other subterranean matter come out of the ground. The exact location of where they come out of is called a vent. A volcano usually has more than one vent. The following table lists three volcanoesand the date of the last eruption:

Eruptions can be violent or quiet. Some eruptions send lava high above the surface in spectacular fountain shapes. Violent eruptions such as these often includechunks of solid rock that were blown off the interior walls of the vent. Quiet eruptions consist of lava simply flowing out of vents. Both types of eruptions can also have gasses, such as sulfur andfluorine gas, coming out of vents.
Cooling and Inactive Stage
Even after a volcano stops erupting, gasses and vapors are still released. Some volcanoes, however, can end one period of eruptions andbegin another after many years. Eventually, the volcano reaches the cooling stage. While the volcano cools, it reduces in size from water and weather erosion.
Types of Volcanoes
The different types...