A volcano is an opening in the surface of the earth that emanates melted rocks, or magma, ashes, water vapor and gases. All this comes from huge underground deposits. All the melted material that reaches the surface of the earth is called LAVA.

The lava, contrary to the common opinion, does not emerge from the crater, with the exception of some strong eruptions. In most of the cases, the lava emerges from existing fissures on the sides or the base of the volcano.

When a volcano erupts, the lava flows violently and breaks into fragments, forming a material that is commonly known as PYROCLASTIC; when this material enters in contact with the air, it gets cold and forms the VOLCANIC BOMBS. The smallest fragments are called SLAG, and the material that looks like dust and cold sand is called VOLCANIC ASHES.

The main components of the lava are silicon oxide, aluminum, iron, manganese, calcium, sodium and potassium. The most common is the silicon oxide. The places on the surface of the earth from which gases emerge are called FUMAROLES.

Most of the volcanoes occasionally enter in activity and most of the time they remain inactive. For the welfare of humanity, only a few of them are in continuous eruption.

The period of eruptive activity can last from one hour to several years. This is the case of the Pacaya volcano. The peaceful intervals between eruptions can last months, decades and in a few occasions, even centuries. However, up to this date, they have not yet discovered a safe measure to predict the eruptions.

Lifetime:
The lifetime of volcanoes can be from a few months to thousands of years.

Active Volcanoes:
The active volcanoes are those who enter in eruptive activity.

Sleeping Volcanoes:
The sleeping volcanoes are those that maintain several signs of activity, like thermal waters, or that have sporadically enter in activity.

Extinct Volcanoes:
The extinct volcanoes are those who were active long time ago and do not show any indication of reactivity for the future.

An interesting fact that we must mention is the fact that some of the most devastating eruptions have been from volcanoes that people thought were dead. For example, the eruption of the Vesuvius volcano in Italy destroyed the cities of Pompeii and Herculean in the year 99 before Christ.

In Guatemala there are 324 eruptive sources. Some of them are big (volcanoes) and some are small (in certain cases they are known as hills). The Federación Nacional de Andinismo (The National Mountain-Climbing Federation) recognizes 37 volcanoes and the Instituto Geográfico Nacional (National Geographic Institute) recognizes 32.

Many of these volcanoes have been identified as hills, since they are covered with vegetation or have lost its shape. For example, the Quetzaltepeque volcano, located in the town of the same name, in the Department of Chiquimula, is known as Chiramay Hill; and the La Gabia volcano located in the town of Pueblo Nuevo Viñas, in Santa Rosa is not recognized by The National Mountain-Climbing Federation, neither by the National Geographic Institute.

Some interesting eruptions that have occurred
since the times of the Conquest are: