Even volcanic eruptions that are considered minor can cause a great deal of damage, eject hundreds or thousands of tons of ash, rock, or lava, and have the potential to be very deadly. Generally, volcanic eruptions are classified as minor, moderate, or major, and of the 13 to 17 volcanoes that erupt yearly on average about half are minor. Usually only two or three are considered to be major.
However, there is a fourth classification that is not often used because it deals with an eruption from a kind of volcano that is extremely rare. The classification is catastrophic, and it refers to the eruption of a super volcano. Note that if a major eruption results in a great loss of life or major destruction, such as in the case of the eruption of Krakatoa where most of the volcano was literally blown away, some scientists may refer to this as catastrophic, but for the purposes of this discussion, that classification is only used in reference to a super volcano.
Defining super volcanoes
To understand what a super volcano is, it is best to look deeper into what volcanoes are and how they function. The difference between regular volcanoes and super volcanoes should then be readily apparent.
Volcanoes are formed when molten rock from the mantle of the earth works its way through fissures and vents to the surface. Along the way, this super heated rock usually melts surrounding rocks and produces a chamber that fills with hot, liquid rock to form a magma chamber. The magma chamber may be located relatively near the surface, or it can be many miles deep. Occasionally it can even link to other nearby magma chambers. One thing that is common in most volcanoes, though, is the size of the chambers are often similar; usually around 5 cubic miles or less. To make it a little easier to visualize, this is less than 2 miles by 2 miles, 2 miles deep. That is obviously a lot of liquid rock.
Occasionally, the chamber is substantially larger, and these larger chambers usually lead to the longer lasting or more violent eruptions. This is the case of Vesuvius and Kilauea. Eruptions from these can be classified as major eruptions.
The heart of a super volcano
Very rarely, a truly immense magma chamber forms. This is the heart of a super volcano. Yellowstone National Park is an example of a super volcano, though there have been no catastrophic eruptions in recorded history, thankfully. For many years, scientists have been attempting to map the size of the magma pocket that exists beneath the park, most of which is actually a shallow volcanic caldera of huge proportions. There are some problems with figuring out the size, and there is some conflicting data. However, some of the more moderate estimates place the pocket at about 20 miles wide, 50 miles long, and as much as 30 miles deep. If true, that would be 30,000 cubic miles of magma, or 6,000 times more than in the ‘normal’ volcano.
Worse yet, we know that it will erupt one day, we just don’t know when. It might be tomorrow; it might not be for ten thousand years. We do know, however, that when it does, it will live up to its classification: Catastrophic.
If it was to erupt today, this is a sampling of what we’d see (NOTE: this is extrapolation, since nobody has been around to witness the eruption of a super volcano.) There would be wide spread earthquakes of large magnitude felt in all states near Yellowstone and possibly from ocean to ocean. When the eruption actually occurred, there would be numerous major vents, spewing ash and lava. This is an advantage to us, as the more there are, the more material can be vented and the shorter that the eruption will probably last. If there are only a few vents, the eruptions could continue for years.
Depending on the prevailing winds, the ash would cover roughly half of the US. Crops would fail if the eruption took place in the spring or summer, and average temperatures would fall, globally, as ash in the atmosphere would block sunlight. Even if the eruptions were very short lived, lasting just days, this effect would be around for years because fine ash in the upper atmosphere takes a very long time to settle back to the ground.
Since the US, especially the plains states, produces an enormous amount of crops to feed people worldwide, every nation on Earth would be impacted by such an eruption, either directly or indirectly, and most likely both.
Again, though, we don’t know when it will erupt, and the scientific data collection continues. It is far too early to panic, and panic will do little good in any event. One thing is for sure. Super volcanoes have shaped our world for most of the world’s history, and they will continue to do so. Much of that change has been beneficial. We can be thankful, though, that they occur so rarely.
