The mechanics of how volcanoes erupt is rather complicated, and there are stages that are critical to it. A volcano is like a tunnel into the earth's how interior, where molten rock flows. Another thing is that magma flow generated magnetic force, and has affected.
Volcanoes are the oldest features of the earth when the mantle formed over its molten core, tectonic plates formed one big continent called Pangaea. A volcano is usually found along with open points in tectonic plates (jigsaw pieces) that float on a sea of magma. These geological structures are vents that lead into the earth's interior.
What really makes a volcano so destructive is the molten rock or magma, this the earth's upper mantle or lower crust that is melted by the head of the earth's molten core. Up on top is the vent-hole (volcano) made of rock that is pushed up or down, depending on the movement of tectonic plates. Another material that is vented out by volcanoes is dissolved gases from inside the mantle. Most of the time, everything is regular, and the earth continues its usual activities. If a volcano decides to be active, there are several causes.
Should these three conditions be present, an eruption is not far behind and will have a great impact too. They are magmatic buoyancy, pressure causes by gases inside channels in the crust, and when the magma chambers are locked and loaded with magma. These conditions will prime the volcano for an eruption at any time.
The severity of eruptions depends on the pressure, density, and other factors that are studied by volcanologists to better predict an eruption. When rock melts under the crust, it retains then same mass with a rise in its volume. The melted rock is less solid and lighter, is very distinguishable from the solid crust. Lighter magma rises as pressures push it up, and is buoyant as well. Volcanic explosions will be a great possibility when magma is more liquid than its surrounding rock layers, with pressure generated. It will be expelled, and nothing can stop it from coming out.
The inside of the earth is closed, with openings to be compared to a champagne bottle. Open the cork, the pressure inside will be released. The earth is the champagne bottle, the wine inside is the magma. There are several kinds of magma like the andesitic and rhyolitic with contents that include water, sulfur dioxide, and carbon dioxide. More dissolved gas present in magma is not so, but the pressure in the vents makes the difference.
When magma moves upward, and water in it is less soluble, and excess water is released as bubbles in it. Moving upward water is separated from magma, which creates more pressure caused by vaporizing water. Gas volume should never exceed the 75% margin it becomes very pressurized, and an imminent explosion might follow. When it does blow, there will be pyroclasts that are harmful to animals, becoming a cloud of deadly ash (normal or super-heated). Every one of these stages is a prelude to a small or larger volcanic explosion. Depending on the pressure or kind of magma, how much pressure is produced by vaporized water. All these lead to the earth's fury before a volcano blows.
Volcanologists are studying volcanoes with a frenzy and yet no accuracy when an eruption will happen. Improvements have been gained but based on the frequency of eruptions known about a volcano. There are better chances of detecting an eruption from active volcanoes. Another method is to detect seismic activity (earthquakes), deformations on the ground, and gas emitted that are signs of probable eruption. One good example of an accurate guess was Mt. Pinatubo in 1991, which allowed early evac from surrounding areas around the active volcano.
Related Article: What Causes a Volcano to Erupt, and How Do Scientists Predict Eruptions?
