John Mysliwiec
Conversations with the Earth

November 29th, 2012

Volcanoes

A volcano is a landform that generally is circular in cross-section that is constructed from lava and tephra erupted onto the Earth’s surface, usually the crust. The opening through which the lava and tephra are emitted is called the volcanic vent. Lava is magma that reaches the Earth’s surface. Magma is melted rock at high pressure and temperature. Magma rises because it is initially less dense than the rock surrounding rock. It eventually equals the density of the surrounding rock and becomes a magma chamber. Tephra is pumice or ash that is blown into the air during eruptions. Volcanoes are generally found where tectonic plates converge and diverge; but are usually not created where tectonic plates slide past one another. As a result volcanoes can be found in all sorts of climate locations. There are four primary types of volcanoes which all have varying effects on the environment. This paper will explore these various types of volcanoes and show how they differ, as well as giving examples of eruptions for each of the types discussed.

Principle Types of Volcanoes

Cinder cones:

Cinder cones are built from particles and blobs of congealed lava ejected from a single vent; they are the simplest forms of volcanoes. Gas charged lava is violently blown into the air and breaks up into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most of these types of volcanoes have a bowl shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. Lava flow can flow from a breach on the side of the crater or a vent from an outside flank. Lava actually rarely comes from the top because the unmolded cinders are too weak to support the pressure exerted by molten rock as it rises to the