Traditional media do not hesitate to cover volcanic eruptions and their destructive potential, but generally they do not do much to explain their functioning or basic characteristics. Today we are going to do a brief review of the parts of a volcano, its most relevant details, and other associated events.
Parts of a volcano: More than we think
Volcanoes are usually classified according to their levels of activity and the type of eruption they record. For example, there are important differences between a shield volcano like the Hawaiian Kīlauea (which is considered more "tranquil", but no less threatening), and an andesitic volcano that can react with extreme violence, almost without warning.
However, there are several common elements worth highlighting. Generally, the diagrams used to describe the parts of a volcano take as a model the stratovolcano (think of the Chilean Osorno, the Mexican Popocatépetl, or the Spanish Teide), a decision that helps a lot in the visualization process.
The parts of a volcano
- Magma chamber: It all starts here. It is an underground reservoir containing magma at very high pressure. The eruption itself is the product of its escape to the surface.
- Rock bed
- Volcanic chimney: In essence, the main exit route for magma. An interesting fact is that chimneys can be connected to magma chambers or not. One of those exceptions is the kimberlite pipe, source of diamonds and other precious stones.
- Base
- Sheet or sill: This describes a tabular mass (i.e., table-shaped) of magmatic rock that installs between very ancient layers of sedimentary rock, or layers of volcanic tuff. The sills represent one of several forms of "intrusion" in geology.
- Fissure or dike: Another example of intrusion. Its thickness can vary considerably (from a few millimeters to several meters), traversing preexisting layers or rock bodies. Its tendency is towards the vertical.
- Layers of ash: Volcanic ash tends to be hard, abrasive, with very small particles (less than 2 millimeters in diameter), insoluble in water, conductive, and with corrosive properties when exposed to humidity.
- Cone
- Layers of lava: The term "lava" simply identifies the expelled magma that managed to reach the surface. Its viscosity is about 100,000 times that of water, but that does not prevent it from traveling enormous distances before cooling and becoming solid.
- Throat
- Secondary or parasitic cone
- Lava flow: Also known as a "flow". A flow with linear characteristics descends along the slope, while it can form large fields if it emerges from fissures. There are three basic types of flow: ʻAʻā or "blocky", Pāhoehoe or "smooth", and pillow, shaped like small cushions.
- Fumarole
- Crater: The "mouth" of the volcano, so to speak. It can take a cone shape at the top, or be a hole in the ground where lava stirs. There are also volcanoes that are all crater and almost no mountain (such as the so-called "maar"). If a volcano manages to empty a large part of its magma chamber, the subsequent collapse gives rise to a caldera.
- Eruption column: Or alternatively, "ash cloud". However, ash is just one component. Columns also emit pyroclast or tephra, that is, fragments of solid material that were expelled during the eruption. If the fragments are more than 64 millimeters in diameter, they are called "volcanic bombs".
Conclusion
We hope this quick guide on the parts of a volcano serves as a starting point, but we want to emphasize that: This is a starting point, not a complete article. Our idea is not to imitate the Rincón del Vago, take what appears here and expand your content when you need to develop it. Good luck!
