For thousands of years, volcanoes were thought to be as a result of angry Gods, and could never be thought of as a natural occurrence that has been going on since the forming of the planet. They are pretty mysterious when you think of it. We stand on solid ground, unaware of the potential for danger when living near one, and it isn’t until it’s too late for those who may have never seen one erupt, or know that they eventually do for that matter.
Over the years, man has accumulated knowledge about these natural occurrences, and has used that knowledge to prepare for evacuating the area that poses the most danger. Still, hundreds, if not thousands of lives are lost, even today, as a result of an eruption. However, knowledge of what signs to look for of an impending eruption doesn’t provide an answer as to why they erupt.
I think it’s truly amazing how science has made the causes of these eruptions easily understood via illustrations of what takes place below the crater. When you think of it, we are seeing what our earth was all about before any living creature inhabited this planet. No oceans, no vegetation, not anything that would resemble what we now call our comfortable home.
When we see the magnitude of what these eruptions can do as far as changing the landscape, and the damage they cause, it’s no small wonder why they are respected so much. We in the 21st century have little to fear compared to our ancestors. We get plenty of warning before they do erupt as a result of scientific research that allows us to predict with a fair amount of accuracy when they will blow their top.
What actually causes it to happen is when parts of the earth’s upper mantle and lower mantle crust melts, and magma forms. A vent which is an opening for the discharge of gases that are formed, which in itself can be considered a volcano, is what we see and considered an eruption.
The volume of rock inside the earth melts and remains the same size in mass as the volume increases, which produces a melting that is less dense than the rock around it.
The lighter magma rises to the surface, and if the density is less than that of the surrounding rocks, then it reaches the surface and erupts.
Sometimes new magma is injected into chambers already filled with magma of a different composition which forces some of the magma in the chamber to move up through the vent and erupts at the surface. Pretty elementary now that we know, but for those in the past who didn’t, just blame it all on the Gods.